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Chemistry Exam Questions

This document appears to be a student exam containing multiple choice and short answer questions about various chemistry topics. Question 1 asks about isotopes of bromine detected in a mass spectrometer. Question 2 involves naming and drawing structures of halogenoalkanes and their reaction mechanisms. Question 3 is a multiple choice dilution problem involving methanoic acid. Question 4 covers topics about s-block metals, including ionization energies, solubility rules, and isotopic abundances.

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0% found this document useful (0 votes)

121 views86 pages

Chemistry Exam Questions

Uploaded by

successhustlerclub

We take content rights seriously. If you suspect this is your content, claim it here.

Available Formats

Download as RTF, PDF, TXT or read online on Scribd

You are on page 1/ 86

_______________________

Name:
_
3.1.1.2 Mass number and
isotopes _______________________
Class:
_

_______________________
Date:
_

Time: 346 min.

Marks: 324 marks

Comments:

Page 1 of 86
Q1.
A sample of bromine was analysed in a time of flight (TOF) mass spectrometer and found
to contain two isotopes, 79Br and 81Br

After electron impact ionisation, all of the ions were accelerated to the same kinetic
energy (KE) and then travelled through a flight tube that was 0.950 m long.

(a) The 79Br+ ions took 6.69 × 10–4 s to travel through the flight tube.

Calculate the mass, in kg, of one ion of 79Br+

Calculate the time taken for the 81Br+ ions to travel through the same flight tube.

The Avogadro constant, L = 6.022 × 1023 mol–1

KE = mv2 where m = mass (kg) and v = speed (m s–1)

where d = distance (m) and t = time (s)

Mass of one ion of 79Br+ ____________________ kg

Time taken by 81Br+ ions ____________________ s

(5)

(b) Explain how ions are detected and relative abundance is measured in a TOF mass
spectrometer.

___________________________________________________________________

___________________________________________________________________
(2)
(Total 7 marks)

Page 2 of 86
Q2.
Compound A is a halogenoalkane.

(a) Name Compound A.

___________________________________________________________________
(1)

(b) Compound A has a relative molecular mass (Mr) of 134.5

The main isotope of hydrogen is 1H
The main isotope of carbon is 12C
Chlorine consists of two common isotopes, 35Cl and 37Cl, of which 75% is 35Cl
The mass spectrum of A was recorded when A was ionised by electron impact to
form A+ ions.

Draw, on Figure 1, the peaks for the main molecular ions in the mass spectrum of
A.

Figure 1

(2)

Name the mechanism for this reaction.

Outline the mechanism using the structure of A shown.

Include the structure of the product, alcohol B.

Mechanism _________________________________________________________

Outline of mechanism

Page 3 of 86
(4)

(d) Reaction of A with hot, ethanolic potassium hydroxide gives alkene C.

Name the mechanism for this reaction.

State the role of the hydroxide ions.

Outline the mechanism using the structure of A shown.

Include the structure of the product, alkene C.

Mechanism _________________________________________________________

Role of hydroxide ions ________________________________________________

Outline of mechanism

(6)

(e) The infrared spectrum in Figure 2 is that of either alcohol B or alkene C.

Figure 2

Tick the box that shows the correct compound.

Explain your answer with reference to a bond and the wavenumber of its absorption.

Alcohol B Alkene C

Explanation _________________________________________________________

___________________________________________________________________

___________________________________________________________________
(1)

Page 4 of 86
(f) Compound D reacts with dilute aqueous sodium hydroxide in a similar way to A to
form alcohol B.

Explain why D reacts more quickly than A with dilute aqueous sodium hydroxide at
the same temperature.

___________________________________________________________________

___________________________________________________________________
(1)
(Total 15 marks)

Q3.
A student has a 10 cm3 sample of 1.00 × 10–2 mol dm–3 methanoic acid solution. The
student is asked to dilute the methanoic acid solution to a concentration of
2.00 × 10–4 mol dm–3 by adding distilled water.

Which volume of water should be added?

A 200 cm3

B 490 cm3

C 500 cm3

D 510 cm3

(Total 1 mark)

Q4.
This question is about s-block metals.

(a) Give the full electron configuration for the calcium ion, Ca2+

___________________________________________________________________
(1)

(b) Explain why the second ionisation energy of calcium is lower than the second
ionisation energy of potassium.

Page 5 of 86
___________________________________________________________________

___________________________________________________________________

___________________________________________________________________
(2)

___________________________________________________________________
(1)

(d) Give the formula of the hydroxide of the element in Group 2, from Mg to Ba, that is
least soluble in water.

___________________________________________________________________
(1)

(e) A student added 6 cm3 of 0.25 mol dm–3 barium chloride solution to 8 cm3 of 0.15
mol dm–3 sodium sulfate solution.
The student filtered off the precipitate and collected the filtrate.

Give an ionic equation for the formation of the precipitate.

Show by calculation which reagent is in excess.
Calculate the total volume of the other reagent which should be used by the student
so that the filtrate contains only one solute.

Ionic equation _______________________________________________________

Reagent in excess ___________________________________________________

Total volume of other reagent ___________________________________________

___________________________________________________________________

___________________________________________________________________
(3)

(f) A sample of strontium has a relative atomic mass of 87.7 and consists of three
isotopes, 86Sr, 87Sr and 88Sr
In this sample, the ratio of abundances of the isotopes 86Sr :87Sr is 1:1

State why the isotopes of strontium have identical chemical properties.

Calculate the percentage abundance of the 88Sr isotope in this sample.

Why isotopes of strontium have identical chemical properties

___________________________________________________________________

Page 6 of 86
___________________________________________________________________

___________________________________________________________________

Percentage abundance of 88Sr ____________________ %

(4)

(g) A time of flight (TOF) mass spectrum was obtained for a sample of barium that
contains the isotopes 136Ba, 137Ba and 138Ba

The sample of barium was ionised by electron impact.

Identify the ion with the longest time of flight.

___________________________________________________________________
(1)

(h) A 137Ba+ ion travels through the flight tube of a TOF mass spectrometer with a kinetic
energy of 3.65 × 10–16 J
This ion takes 2.71 × 10–5 s to reach the detector.

KE = mv2 where m = mass (kg) and v = speed (m s–1)

The Avogadro constant, L = 6.022 × 1023 mol–1

Calculate the length of the flight tube in metres.

Give your answer to the appropriate number of significant figures.

Length of flight tube ____________________ m

(5)
(Total 18 marks)

Q5.

Page 7 of 86
This question is about atomic structure.

(a) Write the full electron configuration for each of the following species.

Cl−________________________________________________________________

Fe2+_______________________________________________________________
(2)

(b) Write an equation, including state symbols, to represent the process that occurs
when the third ionisation energy of manganese is measured.

___________________________________________________________________

___________________________________________________________________
(1)

Explain your answer.

___________________________________________________________________

___________________________________________________________________
(3)

(d) A sample of nickel was analysed in a time of flight (TOF) mass spectrometer. The
sample was ionised by electron impact ionisation. The spectrum produced showed
three peaks with abundances as set out in the table.

m/z Abundance / %

58 61.0

60 29.1

61 9.9

Give the symbol, including mass number, of the ion that would reach the detector
first in the sample.

Calculate the relative atomic mass of the nickel in the sample.

Give your answer to one decimal place.

Symbol of ion _______________________________________________________

Page 8 of 86
Relative atomic mass _________________________________________________
(3)
(Total 9 marks)

Q6.
Which statement about time of flight mass spectrometry is correct?

The current in the detector is proportional to the ion

A
abundance

B Sample particles gain electrons to form positive ions

Particles are detected in the order of their kinetic

C
energies

D Ions are accelerated by a magnetic field

(Total 1 mark)

Q7.
Chlorine exists as two isotopes 35Cl and 37Cl in the ratio 3:1

Which statement about peaks in the mass spectrum of Cl2 is correct?

A Peaks at m/z = 70 and 74 in the ratio 3:1

Peaks at m/z = 70, 72 and 74 in the ratio

B
9:6:1
Peaks at m/z = 70, 72 and 74 in the ratio
C
9:3:1

D Peaks at m/z = 70 and 72 in the ratio 3:1

(Total 1 mark)

Q8.
A sample of titanium was ionised by electron impact in a time of flight (TOF) mass
spectrometer. Information from the mass spectrum about the isotopes of titanium in the
sample is shown in the table.

m/z 46 47 48 49

Abundance / % 9.1 7.8 74.6 8.5

(a) Calculate the relative atomic mass of titanium in this sample.

Give your answer to one decimal place.

Page 9 of 86
Relative atomic mass of titanium in this sample ____________________
(2)

(b) Write an equation, including state symbols, to show how an atom of titanium is
ionised by electron impact and give the m/z value of the ion that would reach the
detector first.

Equation ___________________________________________________________

m/z value ___________________________________________________________

(2)

(c) Calculate the mass, in kg, of one atom of 49Ti

The Avogadro constant L = 6.022 × 1023 mol−1

Mass ____________________ kg
(1)

(d) In a TOF mass spectrometer the time of flight, t, of an ion is shown by the equation

In this equation d is the length of the flight tube, m is the mass, in kg, of an ion and E
is the kinetic energy of the ions.

In this spectrometer, the kinetic energy of an ion in the flight tube is 1.013 × 10 −13 J

The time of flight of a 49Ti+ ion is 9.816 × 10−7 s

Calculate the time of flight of the 47Ti+ ion.

Give your answer to the appropriate number of significant figures.

Time of flight ____________________ s

(3)
(Total 8 marks)

Q9.
Magnesium exists as three isotopes: 24Mg, 25Mg and 26Mg

(a) In terms of sub-atomic particles, state the difference between the three isotopes of
magnesium.

___________________________________________________________________

Page 10 of 86
___________________________________________________________________

___________________________________________________________________
(1)

(b) State how, if at all, the chemical properties of these isotopes differ.

Give a reason for your answer.

Chemical properties __________________________________________________

___________________________________________________________________

Reason ____________________________________________________________

___________________________________________________________________

___________________________________________________________________
(2)

Magnesium has Ar = 24.3

Use this information to deduce the percentages of the other two magnesium
isotopes present in the sample.
24
Mg percentage = ________ % 26
Mg percentage = ________ %
(4)

(d) In a TOF mass spectrometer, ions are accelerated to the same kinetic energy (KE).

where m = mass (kg) and v = velocity (m s−1)

where d = distance (m) and t = time (s)

In a TOF mass spectrometer, each 25Mg+ ion is accelerated to a kinetic energy of

4.52 × 10−16 J and the time of flight is 1.44 × 10−5 s.
Calculate the distance travelled, in metres, in the TOF drift region.
(The Avogadro constant L = 6.022 × 1023 mol−1)

Distance = __________________ m
(4)
(Total 11 marks)

Q10.

Page 11 of 86
Bromine exists as two isotopes 79Br and 81Br, which are found in almost equal abundance.

Which of the statements is correct?

The first ionisation energy of 79Br is less than the first

A
ionisation energy of 81Br
The atomic radius of 79Br is less than the atomic radius
B
of 81Br
The mass spectrum of C3H7Br has two molecular ion
C
peaks at 122 and 124

D 79
Br is more reactive than 81Br
(Total 1 mark)

Q11.
This question is about time of flight (TOF) mass spectrometry.

(a) The mass spectrum of element Q has peaks with m/z values shown in the table.

m/z 82 83 84 86

Relative intensity 5 3 26 7

Calculate the relative atomic mass of Q and give your answer to one decimal place.
Identify the element Q.

Relative atomic mass of Q ________

Element Q ____________________
(3)

(b) A sample of the element Q consists of several isotopes. All of the Q+ ions in the
sample of Q that has been ionised in a TOF mass spectrometer have the same
kinetic energy.

kinetic energy of each ion = mv2

where m is the mass, in kg, of one ion of an isotope and v is the velocity of an ion in
m s−1

where d is the length, in m, of the flight tube and t is the time taken, in s, for an ion to
reach the detector

The time of flight of a 82Q+ ion is 1.243 × 10−5 s.

Calculate the time of flight of the 86Q+ ion.

Time of flight of the 86Q+ ion _____ s

(3)

Page 12 of 86
(Total 6 marks)

Q12.
This question is about halogenoalkanes.

(a) Chlorine atoms are formed in the upper atmosphere when ultraviolet radiation
causes C–Cl bonds in chlorofluorocarbons (CFCs) to break.

Write two equations to show how chlorine atoms catalyse the decomposition of
ozone.

1. _________________________________________________________________

___________________________________________________________________

2. _________________________________________________________________

___________________________________________________________________
(2)

(b) Chloroethane reacts with potassium hydroxide in the presence of propan-1-ol to

form ethene.

State the role of potassium hydroxide and the role of propan-1-ol in the reaction.

Role of potassium hydroxide ___________________________________________

Role of propan-1-ol ___________________________________________________

(2)

(c) Name and outline a mechanism for the reaction in part (b) between chloroethane
and potassium hydroxide to produce ethene.

Name of mechanism __________________________________________________

Mechanism

(4)

(d) The structure of polymer A is shown.

Page 13 of 86
Draw the structure of the monomer used to form polymer A.
(1)

(e) Chemical analysis shows that a chlorofluoroalkane, B, contains by mass 51.6%

fluorine, 32.1% chlorine and no hydrogen.

Chlorine exists as two isotopes, 35Cl and 337Cl, in the ratio 3:1
Fluorine only exists as one isotope, 19F.

A mass spectrum of B is obtained using electron impact ionisation. The mass

spectrum shows three molecular ion peaks at m/z = 220, 222 and 224.

Determine the formula of each of the three molecular ions of B.

Predict and explain the ratio of the relative abundancies of each of the three
molecular ion peaks at m/z = 220, 222 and 224.

To gain full marks you must show all your working.

___________________________________________________________________

___________________________________________________________________
(6)
(Total 15 marks)

Q13.
Chromatography is used to identify amino acid sequences in compounds.

The dipeptide cysteine-aspartic acid (cys-asp), J, and the dipeptide aspartic acid-cysteine
(asp-cys), K, are shown.

Page 14 of 86
(a) A mixture of the two dipeptides J and K is analysed by gas chromatography
followed by mass spectrometry (GC-MS).

Explain why J and K can be separated by gas chromatography and why mass
spectrometry using electrospray ionisation does not enable you to identify them.

Gas chromatography explanation ________________________________________

___________________________________________________________________

Mass spectrometry explanation _________________________________________

___________________________________________________________________

___________________________________________________________________
(4)

(b) A tripeptide, L, is partially hydrolysed with concentrated hydrochloric acid to produce

two dipeptides and the amino acids alanine (ala), lysine (lys) and serine (ser).

The two dipeptides are separated by chromatography. The diagram below shows
the chromatogram.

Page 15 of 86
The table below contains the Rf values of some dipeptides.

Dipeptide ala-lys ala-ser lys-ser lys-ala ser-ala ser-lys

Rf value 0.55 0.85 0.10 0.20 0.15 0.45

Use the chromatogram in the diagram above and the Rf values in the table to
identify the two dipeptides present in spots M and N.

Use your answers to deduce the order of the amino acids in the tripeptide L.

Dipeptide responsible for spot M ________________________________________

___________________________________________________________________

Dipeptide responsible for spot N _________________________________________

___________________________________________________________________

Order of amino acids in tripeptide L ______________________________________

___________________________________________________________________
(3)
(Total 7 marks)

Q14.
(a) A sample of sulfur consisting of three isotopes has a relative atomic mass of 32.16.
The following table gives the relative abundance of two of these isotopes.

Mass number of isotope 32 33

Relative abundance / % 91.0 1.8

Use this information to determine the relative abundance and hence the mass

Page 16 of 86
number of the third isotope.
Give your answer to the appropriate number of significant figures.

Mass number = ____________________

(4)

(b) Describe how ions are formed in a time of flight (TOF) mass spectrometer.

___________________________________________________________________

___________________________________________________________________
(2)

Explain why it is necessary to ionise molecules when measuring their mass in a TOF
mass spectrometer.

___________________________________________________________________

___________________________________________________________________
(2)
(Total 8 marks)

Q15.
Which of these atoms has the smallest number of neutrons?

A 3
H

B 4
He

C 5
He

D 4
Li

Page 17 of 86
(Total 1 mark)

Q16.
A sample of ethanedioic acid was treated with an excess of an unknown alcohol in the
presence of a strong acid catalyst. The products of the reaction were separated and
analysed in a time of flight (TOF) mass spectrometer. Two peaks were observed at m / z =
104 and 118.

(a) Identify the species responsible for the two peaks.

___________________________________________________________________

___________________________________________________________________
(2)

(b) Outline how the TOF mass spectrometer is able to separate these two species to
give two peaks.

___________________________________________________________________

___________________________________________________________________
(4)
(Total 6 marks)

Q17.
This question is about electron configuration.

(a) Give the full electron configuration of an Al atom and of a Cr3+ ion.

Al atom ____________________________________________________________

Cr3+ ion ____________________________________________________________

(2)

(b) Deduce the formula of the ion that has a charge of 2+ with the same electron
configuration as krypton.

___________________________________________________________________
(1)

Page 18 of 86
(c) Deduce the formula of the compound that contains 2+ ions and 3− ions that both
have the same electron configuration as argon.

___________________________________________________________________
(1)
(Total 4 marks)

Q18.
(a) Explain how ions are accelerated, detected and have their abundance determined in
a time of flight (TOF) mass spectrometer.

___________________________________________________________________

___________________________________________________________________
(3)

(b) Calculate the mass, in kg, of a single 52Cr+ ion.

Assume that the mass of a 52Cr+ ion is the same as that of a 52Cr atom.

(The Avogadro constant L = 6.022 × 1023 mol−1)

___________________________________________________________________

___________________________________________________________________
(1)

Calculate the velocity of the ion using the equation.

(m = mass/kg and v = velocity/ms−1)

___________________________________________________________________

___________________________________________________________________
(2)

(d) Bromine has two isotopes, 79Br and 81Br, in approximately equal abundance. In a
TOF mass spectrometer bromine forms ions with formula [Br2]+

Sketch the pattern of peaks you would expect to see in the mass spectrum of a
sample of bromine.

Page 19 of 86
(2)

(e) A sample of xenon has Ar = 131.31. The sample consists of four isotopes. The
abundances of three of the isotopes are shown in the table below. The data for one
of the isotopes, mXe, is missing.

Isotope 129
Xe 131
Xe 132
Xe m
Xe

% To be
28.0 25.0 27.0
abundance calculated

Use the data to calculate the abundance of isotope mXe and calculate m, the mass
number of mXe. Show your working.

___________________________________________________________________

___________________________________________________________________
(4)
(Total 12 marks)

Q19.
Ions of two isotopes of iron are
53
Fe2+ 56
Fe2+

Which statement is correct?

A The ions of both the isotopes have the electronic

configuration 1s22s22p63s23p64s23d6

B The ions of both the isotopes contains 26 neutrons

Page 20 of 86
C 53
Fe2+ has fewer protons than 56Fe2+

D After acceleration to the same kinetic energy 56Fe2+

will move more slowly than 53Fe2+
(Total 1 mark)

Q20.
The successive ionisation energies for element X are shown in the following graph.

Which element is X?

A Nitrogen

B Phosphorus

C Aluminium

D Boron
(Total 1 mark)

Q21.
Tellurium is the element with atomic number of 52

(a) Using information from the Periodic Table, complete the electron configuration of
tellurium.

[Kr] ______________________________________________________________
(1)

(b) The mass spectrum of a sample of tellurium is shown in the graph.

Page 21 of 86
(i) Use the graph to calculate the relative atomic mass of this sample of tellurium.
Give your answer to one decimal place.

______________________________________________________________

______________________________________________________________
(3)

(ii) Suggest what might cause the relative atomic mass of this sample to be
different from the relative atomic mass given in the Periodic Table.

______________________________________________________________

______________________________________________________________
(1)

___________________________________________________________________
(1)

(d) State the m / z value of the ions that produce the biggest current at the detector
when the spectrum in the graph is recorded.
Give a reason for your answer.

m / z value _________________________________________________________

Reason ____________________________________________________________

___________________________________________________________________

Page 22 of 86
___________________________________________________________________
(2)

(e) The mass spectrum of tellurium also has a small peak at m / z = 64

Explain the existence of this peak.

___________________________________________________________________

___________________________________________________________________
(2)

(f) Predict whether the atomic radius of 124Te is larger than, smaller than or the same as
the atomic radius of 130Te
Explain your answer.

Atomic radius of 124Te compared to 130Te __________________________________

Explanation _________________________________________________________

___________________________________________________________________

___________________________________________________________________
(2)
(Total 12 marks)

Q22.
(a) Table 1 shows some data about fundamental particles in an atom.
Table 1

Particle proton neutron electron

Mass / g 1.6725 × 10–24 1.6748 × 10–24 0.0009 × 10–24

(i) An atom of hydrogen can be represented as 1H

Use data from Table 1 to calculate the mass of this hydrogen atom.

______________________________________________________________
(1)

(ii) Which one of the following is a fundamental particle that would not be
deflected by an electric field?

A electron

B neutron

C proton

Page 23 of 86
Write the correct letter, A, B or C, in the box.

(1)

(b) A naturally occurring sample of the element boron has a relative atomic mass of
10.8.
In this sample, boron exists as two isotopes, 10B and 11B

(i) Calculate the percentage abundance of 10B in this naturally occurring sample
of boron.

______________________________________________________________

______________________________________________________________
(2)

(ii) State, in terms of fundamental particles, why the isotopes 10B and 11B have
similar chemical reactions.

______________________________________________________________

______________________________________________________________
(1)

First Second Third Fourth Fifth

Ionisation energy / kJ mol–

1 799 2420 25 000 32 800

(1)

(d) Write an equation to show the process that occurs when the second ionisation
energy of boron is measured. Include state symbols in your equation.

___________________________________________________________________
(1)

(e) Explain why the second ionisation energy of boron is higher than the first ionisation
energy of boron.

___________________________________________________________________

Page 24 of 86
(1)
(Total 8 marks)

Q23.
The mass spectrum of the isotopes of element X is shown in the diagram.

m/z

(a) Define the term relative atomic mass.

___________________________________________________________________

___________________________________________________________________
(2)

(b) Use data from the diagram to calculate the relative atomic mass of X.

Give your answer to one decimal place.

___________________________________________________________________

___________________________________________________________________
(3)

(c) Identify the ion responsible for the peak at 72

___________________________________________________________________
(1)

Page 25 of 86
(d) Identify which one of the isotopes of X is deflected the most in the magnetic field of
a mass spectrometer. Give a reason for your answer.

Isotope ____________________________________________________________

Reason ____________________________________________________________
(2)

(e) In a mass spectrometer, the relative abundance of each isotope is proportional to

the current generated by that isotope at the detector.

Explain how this current is generated.

___________________________________________________________________

___________________________________________________________________
(2)

(f) X and Zn are different elements.

Explain why the chemical properties of X and Zn are different.

70 70

___________________________________________________________________

___________________________________________________________________
(1)
(Total 11 marks)

Q24.
(a) State the meaning of the term mass number of an isotope.

___________________________________________________________________

___________________________________________________________________
(1)

(b) Give the symbol of the element that has an isotope with a mass number of 68 and
has 38 neutrons in its nucleus.

___________________________________________________________________
(1)

(c) The following shows a simplified diagram of a mass spectrometer.

Page 26 of 86
(i) State what happens to the sample in the parts labelled P and Q.

P ____________________________________________________________

Q ____________________________________________________________
(2)

(ii) In a mass spectrometer, the isotopes of an element are separated.

Two measurements for each isotope are recorded on the mass spectrum.

State the two measurements that are recorded for each isotope.

Measurement 1 _________________________________________________

Measurement 2 _________________________________________________
(2)

(d) A sample of element R contains isotopes with mass numbers of 206, 207 and 208 in
a 1:1:2 ratio of abundance.

(i) Calculate the relative atomic mass of R. Give your answer to one decimal
place.

______________________________________________________________

______________________________________________________________
(3)

(ii) Identify R.

______________________________________________________________
(1)

(iii) All the isotopes of R react in the same way with concentrated nitric acid.

State why isotopes of an element have the same chemical properties.

Page 27 of 86
______________________________________________________________

______________________________________________________________
(1)
(Total 11 marks)

Q25.
The element rubidium exists as the isotopes 85Rb and 87Rb

(a) State the number of protons and the number of neutrons in an atom of the isotope
Rb
85

Number of protons ___________________________________________________

Number of neutrons __________________________________________________

(2)

(b) (i) Explain how the gaseous atoms of rubidium are ionised in a mass
spectrometer

______________________________________________________________

______________________________________________________________
(2)

(ii) Write an equation, including state symbols, to show the process that occurs
when the first ionisation energy of rubidium is measured.

______________________________________________________________
(1)

Element sodium potassium rubidium

First ionisation
494 418 402
energy / kJ mol–1

State one reason why the first ionisation energy of rubidium is lower than the first
ionisation energy of sodium.

___________________________________________________________________

___________________________________________________________________
(1)

Page 28 of 86
(d) (i) State the block of elements in the Periodic Table that contains rubidium.

______________________________________________________________
(1)

(ii) Deduce the full electron configuration of a rubidium atom.

______________________________________________________________
(1)

(e) A sample of rubidium contains the isotopes 85Rb and 87Rb only.
The isotope 85Rb has an abundance 2.5 times greater than that of 87Rb

Calculate the relative atomic mass of rubidium in this sample.

Give your answer to one decimal place.

___________________________________________________________________

___________________________________________________________________
(3)

(f) By reference to the relevant part of the mass spectrometer, explain how the
abundance of an isotope in a sample of rubidium is determined.

Name of relevant part _________________________________________________

Explanation _________________________________________________________

___________________________________________________________________

___________________________________________________________________
(2)

(g) Predict whether an atom of 88Sr will have an atomic radius that is larger than, smaller
than or the same as the atomic radius of 87Rb. Explain your answer.

Atomic radius of 88Sr compared to 87Rb ___________________________________

Explanation _________________________________________________________

___________________________________________________________________

___________________________________________________________________
(3)
(Total 16 marks)

Q26.
The manufacture of food grade phosphoric acid for use in cola drinks begins with the
production of pure white phosphorus from the mineral fluoroapatite, Ca5F(PO4)3

Page 29 of 86
(a) Complete the following equation for the manufacture of phosphorus.

....Ca5F(PO4)3 + 9SiO2 + ....C 9CaSiO3 + CaF2 + ....CO + ....P

(1)

(b) As the phosphorus cools, it forms white phosphorus, P4

Give the oxidation state of phosphorus in each of the following.

P4______________________________

H3PO4___________________________
(2)

(c) Fertiliser grade phosphoric acid is manufactured from sulfuric acid and calcium
phosphate.
Use the following precise relative atomic mass data to show how mass spectrometry
can be used to distinguish between pure sulfuric acid (H2SO4) and pure phosphoric
acid (H3PO4) which both have Mr = 98 to two significant figures.

Atom Precise relative atomic mass

1
H 1.00794

16
O 15.99491

31
P 30.97376

32
S 32.06550

___________________________________________________________________

___________________________________________________________________
(1)

(d) Concentrated phosphoric acid is used as a catalyst in the hydration of propene to

form the alcohol CH3CH(OH)CH3 as the main organic product.
The industrial name for this alcohol is isopropyl alcohol.

(i) State the meaning of the term catalyst.

______________________________________________________________

______________________________________________________________
(1)

(ii) State the meaning of the term hydration.

______________________________________________________________

Page 30 of 86
______________________________________________________________

______________________________________________________________
(1)

(iii) Write an equation for the hydration of propene to form isopropyl alcohol.
Give the IUPAC name for isopropyl alcohol.

Equation ______________________________________________________

IUPAC name ___________________________________________________

(2)
(Total 8 marks)

Q27.
The mass spectrum of a sample of krypton taken from a meteorite is shown below.

(a) Use this spectrum to calculate the relative atomic mass of this sample of krypton.
Give your answer to one decimal place.

Explain why the value you have calculated is slightly different from the relative
atomic mass given in the Periodic Table.

___________________________________________________________________

___________________________________________________________________
(4)

Page 31 of 86
(b) State how krypton is ionised in the mass spectrometer.

Write an equation, including state symbols, to show the reaction that occurs when
the first ionisation energy of Kr is measured.

Sometimes the mass spectrum of Kr has a very small peak with an m/z value of 42.
Explain the occurrence of this peak.

___________________________________________________________________

___________________________________________________________________
(5)
(Total 9 marks)

Q28.
Mass spectrometry can be used to identify isotopes of elements.

(a) (i) In terms of fundamental particles, state the difference between isotopes of an
element.

______________________________________________________________

______________________________________________________________
(1)

(ii) State why isotopes of an element have the same chemical properties.

______________________________________________________________

______________________________________________________________
(1)

(b) Give the meaning of the term relative atomic mass.

___________________________________________________________________

___________________________________________________________________
(2)

(c) The mass spectrum of element X has four peaks. The table below gives the relative
abundance of each isotope in a sample of element X.

Page 32 of 86
m/z 64 66 67 68

Relative abundance 12 8 1 6

(i) Calculate the relative atomic mass of element X.

Give your answer to one decimal place.

______________________________________________________________

______________________________________________________________
(3)

(ii) Use the Periodic Table to identify the species responsible for the peak at
m/z = 64

______________________________________________________________
(2)

(d) Suggest one reason why particles with the same mass and velocity can be
deflected by different amounts in the same magnetic field.

___________________________________________________________________

___________________________________________________________________
(1)

(e) Explain how the detector in a mass spectrometer enables the abundance of an
isotope to be measured.

___________________________________________________________________

___________________________________________________________________
(2)
(Total 12 marks)

Q29.
Define the term mass number of an atom.

The mass number of an isotope of nitrogen is 15. Deduce the number of each of the
fundamental particles in an atom of 15N

_______________________________________________________________________

Page 33 of 86
_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________
(Total 3 marks)

Q30.
(a) Define the term relative atomic mass.

An organic fertiliser was analysed using a mass spectrometer. The spectrum

showed that the nitrogen in the fertiliser was made up of 95.12% 14N and 4.88% 15N

Calculate the relative atomic mass of the nitrogen found in this organic fertiliser.
Give your answer to two decimal places.

___________________________________________________________________

___________________________________________________________________
(4)

(b) In a mass spectrometer, under the same conditions, 14N+ and 15N+ ions follow
different paths. State the property of these ions that causes them to follow different
paths.

State one change in the operation of the mass spectrometer that will change the
path of an ion.

___________________________________________________________________

___________________________________________________________________
(2)

State and explain whether or not you would expect the chemical reactions of the
nitrogen compounds in the synthetic fertiliser to be different from those in the
organic fertiliser. Assume that the nitrogen compounds in each fertiliser are the
same.

___________________________________________________________________

Page 34 of 86
___________________________________________________________________

___________________________________________________________________

___________________________________________________________________
(2)
(Total 8 marks)

Q31.
The manufacturer supplying concentrated ethanoic acid for the production of vinegar also
supplied other acids. The label had come off a batch of one of these other acids.
A sample of this unknown acid was analysed and found to contain 54.5% of carbon and
9.10% of hydrogen by mass, the remainder being oxygen.

(a) Use these data to calculate the empirical formula of the unknown acid.
Show your working.

___________________________________________________________________

___________________________________________________________________
(3)

(b) A sample of the unknown acid was analysed in a mass spectrometer. The mass
spectrum obtained is shown below.

Use the mass spectrum to determine the Mr of the unknown acid.

___________________________________________________________________
(1)

Page 35 of 86
(c) Use your answers from parts (a) and (b) to determine the molecular formula of the
unknown acid.
(If you could not answer part (b), you should assume that the Mr of the acid is 132.0
but this is not the correct value.)
Show your working.

___________________________________________________________________

___________________________________________________________________
(2)
(Total 6 marks)

Q32.
A mass spectrometer can be used to investigate the isotopes in an element.

(a) Define the term relative atomic mass of an element.

___________________________________________________________________

___________________________________________________________________
(2)

(b) Element X has a relative atomic mass of 47.9

Identify the block in the Periodic Table to which element X belongs and give the
electron configuration of an atom of element X.

Calculate the number of neutrons in the isotope of X which has a mass number 49

___________________________________________________________________

___________________________________________________________________
(3)

(c) The mass spectrum of element Z is shown below.

Use this spectrum to calculate the relative atomic mass of Z, giving your answer to
one decimal place.

Identify element Z.

Page 36 of 86
___________________________________________________________________

___________________________________________________________________

___________________________________________________________________
(4)

(d) State how vaporised atoms of Z are converted into Z+ ions in a mass spectrometer.

State and explain which of the Z+ ions formed from the isotopes of Z in part (c) will
be deflected the most in a mass spectrometer.

___________________________________________________________________

___________________________________________________________________
(4)

(e) Explain briefly how the relative abundance of an ion is measured in a mass
spectrometer.

___________________________________________________________________

Page 37 of 86
___________________________________________________________________

___________________________________________________________________
(2)
(Total 15 marks)

Q33.
In 1913 Niels Bohr proposed a model of the atom with a central nucleus, made up of
protons and neutrons, around which electrons moved in orbits. After further research, the
model was refined when the existence of energy levels and sub-levels was recognised.

(a) Complete the following table for the particles in the nucleus.

Particle Relative charge Relative mass

proton

neutron
(2)

(b) State the block in the Periodic Table to which the element tungsten, W, belongs.

___________________________________________________________________
(1)

(c) Isotopes of tungsten include 182W and 186W

(i) Deduce the number of protons in 182W

______________________________________________________________
(1)

(ii) Deduce the number of neutrons in 186W

______________________________________________________________
(1)

(d) In order to detect the isotopes of tungsten using a mass spectrometer, a sample
containing the isotopes must be vaporised and then ionised.

(i) Give two reasons why the sample must be ionised.

1. ____________________________________________________________

2. ____________________________________________________________
(2)

(ii) State what can be adjusted in the mass spectrometer to enable ions formed by
the different isotopes to be directed onto the detector.

______________________________________________________________
(1)

(e) State and explain the difference, if any, between the chemical properties of the

Page 38 of 86
isotopes 182W and 186W

Difference __________________________________________________________

Explanation _________________________________________________________

___________________________________________________________________
(2)

(f) The table below gives the relative abundance of each isotope in the mass spectrum
of a sample of tungsten.

m/z 182 183 184 186

Relative abundance /% 26.4 14.3 30.7 28.6

Use the data above to calculate a value for the relative atomic mass of this sample
of tungsten. Give your answer to 2 decimal places.

___________________________________________________________________

___________________________________________________________________
(2)
(Total 12 marks)

Q34.
In one model of atomic structure, the atom has a nucleus surrounded by electrons in
levels and sub-levels.

(a) Define the term atomic number.

___________________________________________________________________
(1)

(b) Explain why atoms of an element may have different mass numbers.

___________________________________________________________________
(1)

(c) The table below refers to a sample of krypton.

Relative m/z 82 83 84 86

Relative abundance / % 12 12 50 26

(i) Name an instrument which is used to measure the relative abundance of

isotopes.

______________________________________________________________

(ii) Define the term relative atomic mass.

Page 39 of 86
______________________________________________________________

(iii) Calculate the relative atomic mass of this sample of krypton.

______________________________________________________________

______________________________________________________________
(5)

(d) Give the complete electronic configuration of krypton in terms of s, p and d sub-
levels.

___________________________________________________________________
(1)

(e) In 1963, krypton was found to react with fluorine. State why this discovery was
unexpected.

___________________________________________________________________
(1)

(f) Use a suitable model of atomic structure to explain the following experimental
observations.

(i) The first ionisation energy of krypton is greater than that of bromine.

______________________________________________________________

(ii) The first ionisation energy of aluminium is less than the first ionisation energy
of magnesium.

______________________________________________________________

______________________________________________________________
(4)
(Total 13 marks)

Q35.
(a) Complete the following table.

Relative mass Relative charge

Neutron

Electron
(2)

(b) An atom has twice as many protons as, and four more neutrons than, an atom of
9
Be. Deduce the symbol, including the mass number, of this atom.

___________________________________________________________________

Page 40 of 86
(2)

(c) Draw the shape of a molecule of BeCl2 and the shape of a molecule of Cl2O. Show
any lone pairs of electrons on the central atom. Name the shape of each molecule.

BeCl2 Cl2O

Name of shape Name of shape

(4)

(d) The equation for the reaction between magnesium hydroxide and hydrochloric acid
is shown below.

Mg(OH)2(s) + 2HCl(aq) → MgCl2(aq) + 2H2O(l)

Calculate the volume, in cm3, of 1.00 mol dm–3 hydrochloric acid required to react
completely with 1.00 g of magnesium hydroxide.

___________________________________________________________________

___________________________________________________________________
(4)
(Total 12 marks)

Q36.
Chlorine has two isotopes, 35Cl and 37Cl. The number of molecular ion peaks in the mass
spectrum of a sample of Cl2 is

A 2

B 3

C 4

D 5
(Total 1 mark)

Q37.
(a) Complete the following table.

Relative mass Relative charge

Page 41 of 86
Proton

Electron
(2)

(b) An atom of element Q contains the same number of neutrons as are found in an
atom of 27A1. An atom of Q also contains 14 protons.

(i) Give the number of protons in an atom of 27A1.

______________________________________________________________

(ii) Deduce the symbol, including mass number and atomic number, for this atom
of element Q.

______________________________________________________________
(3)

(c) Define the term relative atomic mass of an element.

___________________________________________________________________

___________________________________________________________________
(2)

(d) The table below gives the relative abundance of each isotope in a mass spectrum of
a sample of magnesium.

m/z 24 25 26

Relative abundance (%) 73.5 10.1 16.4

Use the data above to calculate the relative atomic mass of this sample of
magnesium.
Give your answer to one decimal place.

___________________________________________________________________

___________________________________________________________________
(2)

(e) State how the relative molecular mass of a covalent compound is obtained from its
mass spectrum.

___________________________________________________________________

___________________________________________________________________
(1)
(Total 10 marks)

Page 42 of 86
Q38.
(a) One isotope of sodium has a relative mass of 23.

(i) Define, in terms of the fundamental particles present, the meaning of the term
isotopes.

______________________________________________________________

(ii) Explain why isotopes of the same element have the same chemical properties.

______________________________________________________________

(iii) Calculate the mass, in grams, of a single atom of this isotope of sodium.
(The Avogadro constant, L, is 6.023 × 1023 mol–1)

______________________________________________________________

______________________________________________________________
(5)

(b) Give the electronic configuration, showing all sub-levels, for a sodium atom.

___________________________________________________________________
(1)

___________________________________________________________________

___________________________________________________________________
(1)

(d) An atom has half as many protons as an atom of 28Si and also has six fewer
neutrons than an atom of 28Si. Give the symbol, including the mass number and the
atomic number, of this atom.

___________________________________________________________________
(2)
(Total 9 marks)

Q39.
(a) State the relative charge and relative mass of a proton, of a neutron and of an
electron.
In terms of particles, explain the relationship between two isotopes of the same
element.
Explain why these isotopes have identical chemical properties.

___________________________________________________________________

Page 43 of 86
___________________________________________________________________

___________________________________________________________________

___________________________________________________________________
(7)

(b) Define the term relative atomic mass. An element exists as a mixture of three
isotopes.
Explain, in detail, how the relative atomic mass of this element can be calculated
from data obtained from the mass spectrum of the element.

___________________________________________________________________

___________________________________________________________________
(7)

Page 44 of 86
(Total 14 marks)

Q40.
Assuming that chlorine exists as two isotopes, and that hydrogen and carbon exist as one
isotope each, how many molecular ion peaks will be shown in the mass spectrum of
C4H6Cl4?

A 2

B 3

C 4

D 5
(Total 1 mark)

Page 45 of 86
Mark schemes

Q1.
(a) = 79 / (1000 × 6.022 × 1023) = 1.31 × 10–25 kg
1

Then either follow method 1 (or method 2 below)

Do not mix and match methods

Method 1

= 0.950 / 6.69 × 10–4

= 1420 ms–1

In method 1, M2 can be awarded in M3

KE = ½ mv2

= ½ × 1.312 × 10–25 × (1420)2

= 1.32 × 10–19 J
Mark consequential to their velocity and mass. Allow mass of
79 etc.
1

V81 =

= √ 1.963 × 106

= 1.40 × 103 ms–1

(allow 1.398 × 103 - 1.402 × 103)

Mark consequential to their velocity and mass. Allow mass of
81 etc.
1

= 6.80 × 10–4 s
Mark consequential to their M4
Accept 6.77 – 6.80 × 10–4 s
1

Method 2

m1(d/t1)2 = m2 (d/t1)2

or
m1 / t12 = m2 / t22
1

Page 46 of 86
t22 = t12 (m2/m1)
Or
t22 = (6.69 × 10–4)2 × (81/79)
1

t22 = 4.59 × 10–7

Mark consequential to their M3

t = 6.77 × 10–4 s
Mark consequential to their M4
Accept 6.77 – 6.80 × 10–4 s
1

(b) ion hits the detector / negative plate and gains an electron
1
Not positive plate

(relative) abundance is proportional to (the size of) the current

1
[7]

Q2.
(a) 3-chloro-2,4-dimethylpentane
This answer only apart from slips with commas and dashes
1

(b) M1 lines at 134 and 136

M1 is for drawing the correct two lines (if other lines are
drawn, penalise M1 (but ignore any additional very small
lines at 135 or 137)
1

M2 line at 134 to be three times higher than line at 136

M2 is for the line at 134 being three times as big as the one
at 136 (ignore other lines)
Accept cross to represent top of lines; if bars drawn – they
should be narrow (less than 10% of division) and clear which
value they refer to.
1

(c) M1 nucleophilic substitution

Page 47 of 86
1

M2 curly arrow from lone pair on O of OH– to C of C–Cl

For SN2: penalise M2 for any additional arrow(s) on NaOH,
or for covalent NaOH; penalise M3 for any additional
arrow(s) to/from the Cl to/from anything else
If curly arrows represent an attempt at an elimination
mechanism, cannot score M2 or M3
1

M3 curly arrow from C–Cl bond to the Cl

Penalise M3 for formal charge on C and/or Cl of C–Cl or
incorrect partial charges on C– Cl; ignore other partial
charges on uncharged atoms
For SN2: penalise M2 for any additional arrow(s) on NaOH,
or for covalent NaOH; penalise M3 for any additional
arrow(s) to/from the Cl to/from anything else
If curly arrows represent an attempt at an elimination
mechanism, cannot score M2 or M3
If SN1 mechanism given (loss of Cl first followed by attack by
OH–) then:
M2 curly arrow from C–Cl bond to the Cl
M3 curly arrow from lone pair on O of OH– to positive C atom
of correct carbocation
penalise M2 for any additional arrow(s) to/from the Cl to/from
anything else
penalise M3 for any additional arrow(s) on NaOH
1

M4 correct structure of alcohol (in any form)

M4 is independent
M4 ignore presence of non-organic products
1

(d) M1 elimination
M1 allow base elimination (but nothing else)
1

M2 base

Page 48 of 86
M2 allow proton acceptor
1

M3 curly arrow from lone pair on O of OH– to H on one of the C atoms adjacent to
the C–Cl
If curly arrows represent an attempt at a substitution
mechanism, cannot score M3 or M4
1

M4 curly arrow from a correct C-H bond adjacent to the C–Cl to a correct C-C
bond. Only award if an arrow is shown attacking the H atom of a correct
adjacent C-H bond in M3
If curly arrows represent an attempt at a substitution
mechanism, cannot score M3 or M4
1

M5 curly arrow from C–Cl bond to the Cl (mark is independent

Penalise M5 for formal charge on C and/or Cl of C–Cl or
incorrect partial charges on C–Cl; ignore other partial
charges on uncharged atoms
1

M6 correct structure of alkene (in any form)

M6 is independent
M6 ignore presence of non-organic products
If E1 mechanism given (loss of Cl first followed by attack by
OH–) then:
M3 curly arrow from C–Cl bond to the Cl
M4 curly arrow from lone pair of OH– to a correct H on the
correct C adjacent to C+ on the carbocation
M5 curly arrow from a correct C-H bond to a correct C-C
bond
penalise M3 for any additional arrow(s) to/from the Cl to/from
anything else
penalise M4 for any additional arrow(s) on KOH
1

(e) C as C=C 1620-1680 cm–1 OR no O-H 3230-3550 cm–1

need the correct compound and an explanation

full wavenumber range or value(s) within the range
on this occasion candidates do not need to refer to the O-H
bond being O-H alcohol as opposed to O-H acid – just
reference to O-H with wavenumbers is required
1

(f) C–Br is weaker than C–Cl or

C–Br has lower bond enthalpy than C–Cl or

C–Br breaks more easily C–Cl

Must compare the C–Br and C–Cl bonds specifically
Ignore references to bond length, size of atoms, shielding,
electronegativity and polarity
Penalise idea that bromine is more reactive than chlorine
1

Page 49 of 86
[15]

Q3.
B
[1]

Q4.
(a) 1s2 2s2 2p6 3s2 3p6 (4s0)
1

(b) M1 In Ca(+) (outer) electron(s) is further from nucleus

Or Ca(+) loses electron from a higher (energy) orbital

Or Ca(+) loses electron from a 4(s) orbital or 4th energy level or 4th energy
shell and K(+) loses electron from a 3(p) orbital or 3rd energy level or 3rd
energy shell
Must be comparative
Allow converse arguments
1

M2 More shielding (in Ca+)

(d) Mg(OH)2
1

(e) Ba2+ + SO42– → BaSO4

Ignore state symbols
1

n BaCl2 (6/1000 × 0.25) = 1.5 × 10–3 and n Na2SO4 = (8/1000 × 0.15) = 1.2 × 10–3

and BaCl2 /barium chloride in excess

Working required or 3 × 10–4 of BaCl2
1

10 cm3 (of 0.15 mol dm–3 sodium sulfate)

or 0.01dm3
1

(f) M1 Same electronic configuration / same number of electrons (in outer shell) / all
have 37 electrons (1)
Ignore protons and neutrons unless incorrect numbers
Not just electrons determine chemical properties
1

M2 = 87.7
Alternative M2:

Page 50 of 86
1

M3 x = 10% (or × = 0.1)

M3 y = 8
1

M4 (% abundance of 88 isotope is 100 – 2x10) = 80(.0)%

M4 % of 88 isotope is 100 – 10y = 80(.0) %
Allow other alternative methods
1

(g) 138
Ba+

(h) M1 = 2.275 × 10–25 (kg)

Calculation of m in kg
If not converted to kg, max 4
If not divided by L lose M1 and M5, max 3
1

M2 v2 = = = 3.2088 × 109

For re-arrangement
1

M3 v= (v = 5.6646 × 104)
For expression with square root
1

M4 v = d/t or d = vt or with numbers

M5 d = (5.6646 × 104 × 2.71 × 10–5) = 1.53 - 1.54 (m)

M5 must be to 3sf
If not converted to kg, answer = 0.0485-0.0486 (3sf). This
scores 4 marks
1

Alternative method

M1 = 2.275 × 10–25

M1 Calculation of m in kg
1

M2 v = d/t
M2, M3 and M4 are for algebraic expressions or correct
expressions with numbers

Page 51 of 86
1

M3 d2 =
1

M4 d= (= √ (3.65 × 10–16 × 2 × (2.71 × 10–5)2 / 2.275 × 10–25))

M5 d = 1.53 – 1.54 (m)

M5 must be to 3sf
1
[18]

Q5.
(a) Cl− 1s22s22p63s23p6
1
Fe2+1s22s22p63s23p63d6
1
If [Ne] or [Ar] used then Max 1if both correct
Ignore 4s0
Allow subscripts

(b) Mn2+ (g) ⟶ Mn3+ (g) + e−

1
States symbols are required
Allow Mn2+ (g) − e− ⟶ Mn3+ (g)
Negative charge needed on electron

(c) Al
Mg then CE = 0
1
(Outer) electron in (3)p sublevel / orbital
Not just level or shell
1
Higher in energy / further from the nucleus
so easier to remove OWTTE
Both required for M3
1
Ignore shielding

(d) 58
Ni+

M1 needs mass and charge – allow subscripts

1
Ar= [(58 × 61.0) + (60 × 29.1) + (61 × 9.9)] / 100
1
Ar= 58.9 must be to 1dp
1
[9]

Q6.

Page 52 of 86
A
[1]

Q7.
B
[1]

Q8.

(a)
1

= 47.8
Correct answer scores 2 marks.
Allow alternative methods.
Allow 1dp or more.
Ignore units
1

(b) Ti(g) → Ti+(g) +e−

or Ti(g) + e−→ Ti+(g) +2e−

or Ti(g) − e−→ Ti+(g)

State symbols essential
Allow electrons without − charge shown.
1

46
1

(c) 8.1(37) × 10−26

(d) M1 is for re-arranging the equation

Allow t α square root of m

d = 1.5(47)
This scores 2 marks
Allow this expression for M2

Page 53 of 86
1

= 9.6(14) × 10−7

Correct answer scores 3 marks.

1
[8]

Q9.
(a) 24
Mg has 12n; 25Mg has 13n; 26Mg has 14n

OR They have different numbers of neutrons

(b) No difference in chemical properties

Because all have the same electronic structure (configuration)

OR they have the same number of outer electrons

(c) If fraction with mass 24 = x

Fraction with mass 26 = 0.900 − x

Fraction with mass 25 = 0.100

Ar = 24x + (25 × 0.100) + 26(0.900 − x)

24.3 = 24x + 2.50 + 23.4 −26x

2x = 1.60

x = 0.800 i.e. percentage 24Mg = 80.0(%) (80.0% 3sf)

1
26
Mg = 0.900 − 0.800 = 0.100 ie percentage 26Mg = 10.0(%)
1

(d) m=
1

v2 = 2ke/m or v2 =
1

D = vt =1.48 × 105 × 1.44 × 10−5

D = 2.13 (m)
1

Page 54 of 86
[11]

Q10.
C
[1]

Q11.

(a)
1

84.0
1

Kr
1

(b) 82/(1.243 × 10−5)2 = 86 / t2

So t2 = 86 / 82 × (1.243 × 10−5)2

t2 = 1.6204 × 10−10

t = 1.273 × 10−5 (s)

1
[6]

Q12.
(a) Cl• + O3 ⟶ ClO• + O2

Allow dot in free-radical on either O or Cl.

ClO• + O3 ⟶ 2O2 + Cl•

(b) (KOH acts as a) base

(propan-1-ol acts as a) solvent.

Allow product of reaction between KOH and propan-1-ol /
CH3CH2CH2O− acts as base.
1

(c) (Name of mechanism) Elimination

mechanism: 3 arrows (1 mark each).

Page 55 of 86
3

(d)

(e) This question is marked using levels of response. Refer to the Mark Scheme
Instructions for Examiners for guidance on how to mark this question.

Level 3

All stages are covered & the explanation of each stage is generally correct and
virtually complete. Stages 1 and 2 are supported by correct data. Answer
communicates the whole process coherently and shows a logical progression from
stage 1 to stage 2 and then stage 3.

Steps in stage 3 are in logical order and working is shown. If there is no working for
ratio or statement of ratio then full marks cannot be awarded.

If the formulae of the three molecular ions are not correct (2d) then the
student can’t access Level 3 (any incorrect chemistry drops the student to the
bottom mark within the level they have achieved).
5-6 marks

Level 2

Stage 2 is attempted (2a-2c do not need to be explicitly stated) but the calculation
may contain inaccuracies OR the explanation may be incomplete OR first two
stages are covered and the explanations are generally correct and virtually
complete. Answer is mainly coherent and shows a progression through the first two
stages. Some steps in each stage may be incomplete.

If percentage of carbon is missing or incorrect (1a) then student can’t access

Level 2.
3-4 marks

Level 1

Stage 1 needs to be attempted but may contain inaccuracies.

Page 56 of 86
Stage 3 attempted but may contain inaccuracies / molecular formula not determined.

Answer includes some isolated statements, but these are not presented in a logical
order or show confused reasoning.

1-2 marks

Level 0

Insufficient correct chemistry to warrant a mark.

0 marks
Indicative Chemistry content
Stage 1 (determines empirical formula)
1a 16.3% carbon
1b Divide by Ar
1c Divide by smallest (0.904)
1d Convert ratio in simplest integer (x 2)

C Cl F

= 1.358 = 0.904 = 2.716

3 2 6

Stage 2 (determines formulae of three molecular ions)

2a For E.F. Mr (corresponds to the molecule) = 221
2b since Mr = 221 lies within molecular ion range 220–224
2c Thus empirical formula = molecular formula
2d Three correct formulae
2e Correct Mr for each of three molecules

220 222 224

Stage 3 (explains the ratio of 3 molecular ion peaks)

3a Working
2b Correct (simplified) ratio 9:6:1
Note: 9:3:1 will be a common incorrect answer (max 5).

Working:

220 222 224

Page 57 of 86
and

[15]

Q13.
(a) Gas chromatography explanation

Different retention times / dipeptides appear at different times.

Different balance between solubility in the moving phase / gas carrier and retention
by the stationary phase / column OR different relative affinity for mobile and
stationary phases.
1

Mass spectrometry explanation

Same m/z values.

(Both) dipeptides / J and K have same molecular formula / Mr.

(b) ser-ala
1

ala-lys
1

ser-ala-lys
This order only.
1
[7]

Q14.
(a) Abundance of third isotope = 100 – 91.0 –1.8 = 7.2%
1

= 32.16
1

7.2y = 32.16 × 100 – 32 × 91 – 33 × 1.8 = 244.6

y = 244.6 / 7.2 = 33.97

y = 34
Answer must be rounded to the nearest integer
1

(b) (for electrospray ionisation)

Page 58 of 86
A high voltage is applied to a sample in a polar solvent
1

the sample molecule, M, gains a proton forming MH+

(for electron impact ionisation)

the sample is bombarded by high energy electrons

the sample molecule loses an electron forming M+

Only ions will create a current when hitting the detector

1
[8]

Q15.
D
[1]

Q16.
(a) [CH3OCOCOOH]+
Allow names
1

[CH3OCOCOOCH3]+

Do not allow molecular formula

(b) Positive ions are accelerated by an electric field

To a constant kinetic energy

The positive ions with m / z of 104 have the same kinetic energy as those with
m / z of 118 and move faster
1

Therefore, ions with m / z of 104 arrive at the detector first

1
[6]

Q17.
(a) 1s22s22p63s23p1
1

Page 59 of 86
1s22s22p63s23p63d3

1
If noble gas core used correctly in both then scores 1
Allow subscripts and capitals
Ignore 4s0
(b) Sr2+

Ignore name and correct proton/mass number

Allow Sr+2
1

Q18.
(a) (Ions accelerated by) attraction to negatively charged plate /
electric field
Mark independently
1

Ions detected by gaining electrons

Allow the transfer of electrons
1

Abundance determined by (size) of current flowing

(or amount of electrons gained) in the detector
Allow current is proportional to abundance
1

(b) Mass =

Mass = 8.6(4) × 10−26

(c) V2 = (2 × 1.269 × 10−13) / 8.64 × 10−26

Allow correct rearrangement for V or V2

V = 1.71 × 106 ms−1

Allow ecf from (b) (note if 8.6 × 10−23 in (b) leads to approx.
5.4 × 104 ms−1)
1

(d) Sketch with peaks at 158, 160, 162

Mark independently
1

Page 60 of 86
In ratio 25%:50%:25%
Allow approx. ratio 1:2:1
1

(e) % abundance mXe = 20(%)

Working must be shown
1

131.31 = (0.28129) + (0.25131) + (0.27132) + (0.20m)

131.31 – 104.51 = 0.2m

Mass number = 134

Answer must be an integer
1
[12]

Q19.
D
[1]

Q20.
C
[1]

Q21.
(a) 5s2 4d10 5p4 / 4d10 5s2 5p4
1s 2s 2p 3s 3p6 4s2 3d10 4p6 5s2 4d10 5p4
2 2 6 2

or 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p4
Allow any order but must finish with 5p4
1

(b) (i) or

M1 for top line

127.8
M2 for correct denominator
1
127.8 with no working shown scores 3 marks
1

1
Mark for 100 dependent on top line correct
1

Page 61 of 86
127.8
1

(ii) Other isotopes present / some isotopes absent / different abundances of

isotopes
1

(c) Te+ + e(−) Te

Ignore state symbols
Allow Te2+ + 2e(−) Te
1

(d) 128
Only
1

Most abundant ion (QoL − superlative)

M2 dependent on correct M1
1

(e) 2+ ion formed / 2 electrons removed

Due to 128Te2+ = 2 marks
1

From 128 (Te)

Mark independently
1

(f) Same
If not same CE = 0 / 2
1

(Each isotope has the) same number of protons / same nuclear charge and
same number of electrons / electronic configuration
Ignore more neutrons in 130Te
1
[12]

Q22.
(a) (i) 1.6734 × 10−24 (g)
Only.

1.6734 × 10−27 kg
Not 1.67 × 10−24 (g).
1

(ii) B
1

(b) (i) = 10.8

OR ratio 10:11 = 1:4 OR 20:80 etc

Allow idea that there are 5 × 0.2 divisions between 10 and
11.
1

Page 62 of 86
abundance of 10B is 20(%)

= 10.8

10x + 1100 − 11x = 1080

∴ x = 1100 − 1080 = 20%

Correct answer scores M1 and M2.
1

(ii) Same number of electrons (in outer shell or orbital)

Ignore electrons determine chemical properties.

Same electronic configuration / arrangement

Ignore protons unless wrong.
1

(c) Range between 3500 and 10 000 kJ mol−1

(d) B+(g) B2+(g) + e(−)

B+(g) − e(−) B2+(g)

B+(g) + e(−) B2+(g) + 2e(−)

Ignore state symbol on electron even if wrong.

(e) Electron being removed from a positive ion (therefore needs more energy) /
electron being removed is closer to the nucleus
Must imply removal of an electron.
Allow electron removed from a + particle / species or from a
2+ ion.
Not electron removed from a higher / lower energy level /
shell.
Not electron removed from a higher energy sub-level /
orbital.
Ignore electron removed from a lower energy sub-level /
orbital.
Ignore ‘more protons than electrons’.
Not ‘greater nuclear charge’.
Ignore ‘greater effective nuclear charge’.
Ignore shielding.
1
[8]

Q23.
(a) Average / mean mass of 1 atom (of an element)
1/12 mass of one atom of 12C

Page 63 of 86
If moles and atoms mixed, max = 1
1
Mark top and bottom line independently.
All key terms must be present for each mark.
1

Average / mean mass of atoms of an element

1/12 mass of one atom of 12C

Average / mean mass of atoms of an element ×12

mass of one atom of 12C

(Average) mass of one mole of atoms

1/12 mass of one mole of 12C

(Weighted) average mass of all the isotopes

1/12 mass of one atom of 12C

Average mass of an atom / isotope (compared to C−12) on a scale in which an

atom of C−12 has a mass of 12
This expression = 2 marks.

(b)
1
1

= 72.4
72.4 only
1

(c) Ge+ or germanium+

(72)

Must show ‘+’ sign.

Penalise wrong mass number
1

(d) 70
If M1 incorrect or blank CE = 0/2
Ignore symbols and charge even if wrong.
1

Lowest mass / lowest m/z

Accept lightest.
Accept fewest neutrons.
1

Page 64 of 86
(e) Electron(s) transferred / flow (at the detector)
M1 must refer to electron flow at the detector.
If M1 incorrect CE = 0/2
1

(From detector / plate) to the (+) ion

Do not allow from a charged plate.
1

(f) They do not have the same electron configuration / they have different number
of electrons (in the outer shell)
Ignore electrons determine the properties of an atom.
Ignore they are different elements or different number of
protons.
1
[11]

Q24.
(a) (Total number of) protons and neutrons (in nucleus of atom)
(number of) nucleons
1

(b) Zn
Do not allow Zn−1 or Zn+1 or ZN
Ignore numbers
1

(c) (i) P = ionise (sample)

Allow removing an electron / forms (+) ions
1

Q = accelerate (sample)
Allow speeds (ions) up
Penalise molecules / atoms
1

(ii) m/z
Allow mass / charge
1

(relative) abundance / (relative) intensity

QoL
Allow M1 + M2 in any order
1

(d) (i)
M1 = topline
1
M2 = ÷ 4
1

= 207.3
Only
207.3 = 3 marks

Page 65 of 86
1

(ii) Lead / Pb
Not PB
1

(iii) Same number of electrons (in outer shell) / same electronic configuration
Ignore electrons determine chemical properties
Ignore reference to p and n if correct
Penalise if incorrect
1
[11]

Q25.
(a) 37
These answers only.
Allow answers in words.
1

48
Ignore any sum(s) shown to work out the answers.
1

(b) (i) Electron gun / high speed/high energy electrons

Not just electrons.
Not highly charged electrons.
1

Knock out electron(s)

Remove an electron.
1

(ii) Rb(g) → Rb+(g) + e(–)

OR
Rb(g) + e(–) → Rb+(g) + 2e(–)
OR
Rb(g) - e(–) → Rb+(g)
Ignore state symbols for electron.
1

(c) Rb is a bigger (atom) / e further from nucleus / electron lost from a higher
energy level/ More shielding in Rb / less attraction of nucleus in Rb for outer
electron / more shells
Answer should refer to Rb not Rb molecule
If converse stated it must be obvious it refers to Na
Answer should be comparative.
1

(d) (i) s / block s / group s

Only
1

(ii) 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1

Allow 3d10 before 4s2

Page 66 of 86
Allow in any order.
1

(e) (85 × 2.5) + 87 ×1

3.5
M1 is for top line
1
1

= 85.6
Only
1

(58 × 5) + 87 ×2
7
M185Rb 71.4% and 87Rb 28.6%
M2 divide by 100
1
1

85.6
M3 = 85.6
1

(f) Detector
Mark independently
Allow detection (plate).
1

Current / digital pulses / electrical signal related to abundance

Not electrical charge.
1

(g) Smaller
Chemical error if not smaller, CE = 0/3
If blank mark on.
1

Bigger nuclear charge / more protons in Sr

Not bigger nucleus.
1

Similar/same shielding
QWC
(Outer) electron entering same shell/sub shell/orbital/same
number of shells.
Do not allow incorrect orbital.
1
[16]

Q26.
(a) 2Ca5F(PO4)3+ 9SiO2 +15C9CaSiO3 + CaF2 +15CO + 6P
1

Page 67 of 86
(b) M1 (P4 =) 0

M2 (H3PO4 =) (+) 5
Accept Roman numeral V for M2
2

Mr = 2(1.00794) + 32.06550 + 4(15.99491)

= 98.06102 or 98.0610 or 98.061 or 98.06 or 98.1
Calculations not required

and

H3PO4

Mr = 3(1.00794) + 30.97376 + 4(15.99491)

= 97.97722 or 97.9772 or 97.977 or 97.98 or 98.0
1

(d) (i) A substance that speeds up a reaction OR alters / increases the rate of a
reaction AND is chemically unchanged at the end / not used up.
Both ideas needed
Ignore reference to activation energy or alternative route.
1

(ii) The addition of water (QoL ) to a molecule / compound

QoL- for the underlined words
1

(iii) M1 CH3CH=CH2 + H2O CH3CH(OH)CH3

(C3H6)
For M1 insist on correct structure for the alcohol but credit
correct equations using either C3H6 or double bond not given.

M2 propan-2-ol
2
[8]

Q27.

(a)

M1 for the top line

M2 is for division by 17
1

= 84.0
Not 84
No consequential marking from M1 or M2
Ignore units
1

Page 68 of 86
The Ar in the Periodic table takes account of the other isotopes /
different amounts of isotopes (or words to that effect regarding isotopes)
Award independently
Comparison implied
Isotope(s) alone, M4 = 0
1

(b) (Beam of electrons from) an electron gun / high speed / high energy electrons
1

Knocks out electron(s) (to form a positive ion)

Kr(g) + e– → Kr+(g) + 2e(–)

State symbols must clearly be (g)
1

Kr(g) → Kr+(g) + e(–) / Kr(g) – e(–) → Kr+(g)

The 84Kr isotope

One mark for identifying the 84 isotope
1

Has 2 electrons knocked out / gets a 2+ charge

One mark for the idea of losing 2 electrons (from this
isotope)
1
[9]

Q28.
(a) (i) Different number / amount of neutrons
Not different neutrons
Ignore same protons and/or electrons
CE incorrect statement relating to protons / electrons
1

(ii) Same electron configuration / same number of

electrons (in the outer shell)
Ignore same no of protons
Ignore electrons determine chemical properties
CE if wrong statement relating to protons / neutrons
1

(b) Average mass of 1 atom (of an element)

1/12 mass atom of 12C

Average/mean mass of atoms of an element

1/12 mass of one atom of 12C

Page 69 of 86
(Average) mass of one mole of atoms
1/12 mass of one mole of 12C

(Weighted) average mass of all the isotopes

1/12 mass of one atom of 12C

Average mass of an atom/isotope compared to C-12

on a scale in which an atom of C-12 has a mass of 12
If moles and atoms mixes Max = 1
Mark top and bottom line independently
1/12 on bottom line can be represented as x 12 on top line
This expression = 2 marks
2

= 65.6
If not 27 max 1 mark (for top line)
Mark is for dividing by 27 or string
If evidence of arithmetic or transcription error seen in M1 or
M2 allow consequential M3 and consequential (c)(ii)
65.6 = 3 marks
3

(ii) 64
Zn+

M1 for identifying Zn / zinc

M2 is for the + sign and the 64
M2 is dependent on M1
2

(d) Size of the charge (on the ion) / different charges / different m/z
Allow forms 2+ ions
QWC
1

(e) (ions hit detector and) cause current/(ions) accept

electrons/cause electron flow/electric pulse caused
bigger current = more of that isotope/current proportional to abundance
Implication that current depends on the number of ions
M2 dependent on M1
2
[12]

Q29.
Mass number = number of protons + neutrons (in the nucleus/atom)
Not in a substance or compound or element

Page 70 of 86
1

7 protons and 7 electrons

8 neutrons
1
[3]

Q30.
(a) Average/mean mass of (1) atom(s) (of an element)
1

1/12 mass of one atom of 12C

Accept answer in words
Can have top line × 12 instead of bottom line ÷ 12
1

(Average) mass of one mole of atoms

1/12 mass of one mole of 12C

(Weighted) average mass of all the isotopes

1/12 mass of one atom of 12C

Average mass of an atom/isotope compared to C-12

on a scale in which an atom of C-12 has a mass of 12

Allow 95.12 + 4.88 instead of 100

= 14.05
If not to 2 d.p. then lose last mark
Not 14.04
1

(b) 15
N is heavier/15N has a bigger m/z/different m/z values
Not different no’s of neutrons
Not ionisation potential
1

Electromagnet/electric field/magnet/accelerating
potential or voltage/electric current
1

Same no of electrons (in outer orbital/shell/sub shell)/same

electron configuration

Page 71 of 86
M2 dependent on M1
Not just electrons determine chemical properties
Ignore protons
1
[8]

Q31.
(a) Percentage of oxygen is 36.4%
% of oxygen stated or shown in calculation.
1

Correct calculation of ratios (C 4.54, H 9.10, O 2.28)

Mark is for correct method, dividing % by Ar
1

Empirical formula C2H4O

Allow consequential answer from wrong percentage of
oxygen (max 2 marks).
1

(b) 88
Accept 88.0
Do not penalise correct answer in g.
1

(c) Ratio MF / EF of 2 (88 / 44.0 = 2)

If use 132 / 44 = 3, molecular formula C6H12O3 scores 2
marks.
1

Molecular formula is C4H8O2

Accept consequential answers from (a) and (b)
1
[6]

Q32.

(a) Average/mean mass of (1) atom(s) (of an element)

1/12 mass of one atom of 12C
1
If moles and atoms mixes Max = 1
1

(Average) mass of one mole of atoms

1/12 mass of one mole of 12C

(Weighted) average mass of all the isotopes

1/12 mass of one atom of 12C

Page 72 of 86
Average mass of an atom/isotope compared to C-12 on a scale in
which an atom of C-12 has a mass of 12
This expression = 2 marks

(b) d block
Allow 3d/D
Other numbers lose M1
Ignore transition metals
1

[Ar] 3d24s2

1
Can be written in full
Allow subscripts
3d2 and 4s2 can be in either order

27
1

(c)

(= 1550)
1

(or ∑ their abundances)

If one graph reading error lose M1 and allow consequential
M2 and M3.
If 2 GR errors penalise M1 and M2 but allow consequential
M3
If not 17 or ∑ their abundances lose M2 and M3
1

= 91.2
91.2 = 3 marks provided working shown.
1

Zr/Zirconium
M4 -allow nearest consequential element from M3
accept Zr in any circumstance
1

(d) High energy electrons/bombarded or hit with electrons

accept electron gun
1

knocks out electron(s) (to form ions)

Z+ = 90 deflected most
If not 90 lose M3 and M4
If charge is wrong on 90 isotope lose M3 only
Accept any symbol in place of Z
1

since lowest mass/lowest m/z

Page 73 of 86
Allow lightest
1

(e) (ions hit detector and) cause current/(ions) accept electrons/cause

electron flow
QWC
1

bigger current = more of that isotope/current proportional to abundance

Implication that current depends on the number of ions
1
[15]

Q33.
(a)
Particle Relative Charge Relative mass

Proton +1 1 1

Neutron 0 1 1

Need +1 for proton

(b) d block/ D block;

Or D or d
1

(c) (i) 74;

Not 74.0
1

(ii) 112;
Not 112.0
1

(d) (i) To accelerate/ make go faster;

To deflect/ to bend the beam;

Any order
Not just attract to negative plate
1

(ii) Electromagnet / magnet / electric field /accelerating potential or

voltage;
Not electric current
Not electronic field
1

(e) None/ nothing;

If blank mark on.
If incorrect CE = 0
1

Same number of electrons (in outer orbital/shell)/ both have 74

electrons/same electron configuration;

Page 74 of 86
Not just electrons determine chemical properties
Ignore protons and neutrons unless wrong statement.
1

(f) ;
If transcription error then
M1 = AE = –1 and mark
M2 consequentially
1

= 183.90; allow range from 183.90 – 184.00;

1
[12]

Q34.
(a) Number of protons in the nucleus
1

(b) They may have different numbers of neutrons

(c) (i) Mass spectrometer

(ii) × 12
2

(iii) Ar =
1

= (82 × 12 + 83 × 12 + 84 × 50 + 86 × 26)/100 = 84.16

(d) 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6

(e) Krypton was thought to be an inert gas

(or has 8 electrons in outer shell)
1

(f) (i) Krypton has more protons than bromine

But its outer electrons are in the same shell

(or have similar shielding)
1

(ii) Al electron is in a 3p orbital, magnesium in 3s

Energy of 3p is greater than 3s

1
[13]

Page 75 of 86
Q35.
(penalty for sig fig error =1 mark per question)

(a) neutron: relative mass = 1 relative charge = 0

(not ‘neutral’)
1

electron: relative mass = 1/1800 → 0/negligible or

5.56 × 10–4 → 0 relative charge = –1

(b) 17
O/O17 mass number (Do not accept 17.0)
1

oxygen symbol ‘O’

(if ‘oxygen’ + — ‘mass number = 17’(1))
(if ‘oxygen’+ — ‘mass number = 17’(0))
(if at N 0 given but ≠ 8, treat as ‘con’ for M2)
(if lp on Be, diagram = 0)
(ignore bond angles)
(not dot and cross diagrams)
1

(c)

QoL Linear (1) bent / V-shaped / angular (1)

(mark name and shape independently)
(accept (distorted) tetrahedral)
(if balls instead of symbols, lose M1 – can award M2)
(penalise missing ‘Cl’ once only)
(not ‘non-linear’)
2

(d) M (Mg(NO3)2 = 58(.3) (if At N used, lose M1 and M2)

r
0

moles Mg(OH)2 = 0.0172 (conseq on wrong M2) (answer to 3+ s.f.)

moles HCl = 2 × 0.0172 = 0.0344 or 0.0343 (mol) (process mark)

vol HCl = = 34.3 – 34.5 (cm3) (unless wrong unit)

(if candidate used 0.017 or 0.0171 lose M2)
(just answer with no working, if in range = (4).
if, say, 34 then =(2))

Page 76 of 86
(if not 2:1 ratio, lose M3 and M4)
(if work on HCl, CE = 0/4)
1
[12]

Q36.
B
[1]

Q37.
(a) Proton mass = 1 charge = +1
Electron mass 1/1800 Or 5.6 × 10–4 charge = –1
(Do not accept +1 for proton mass or ‘g’ units)
2

(b) (i) 13
1

(ii) Si
1

Mass number = 28 and atomic number = 14

(Do not accept 28.1 or 28.0 or ‘Silicon’)
5

(c) Mean (average) mass of an atom / all the isotopes

1/12th mass of atom of 12C
Or Mass of 1 mole of atoms of an element (1)
1/12th mass of 1 mole of 12C (1)
Or Average mass of an atom / all the isotopes (1)
relative to the mass of a 12C atom taken as exactly 12 / 12.000 (1)
(Penalise ‘weight’ once only) (Ignore ‘average’ mass of 12C)
(Do not allow ‘mass of average atom’)
2

(d) Ar = (24 × 0.735) + (25 × 0.101) + (26 × 0.164) 1 = 24.4 1

(mark M2 conseq on transcription error or incorrect addition
of %)

(e) Mr = highest m/z value 1

(NOT ‘highest/largest/right-hand’ peak)
3
[10]

Q38.
(a) (i) Atoms with the same number of protons / proton number (1)
NOT same atomic number

with different numbers of neutrons (1)

NOT different mass number / fewer neutrons

(ii) Chemical properties depend on the number or amount of

Page 77 of 86
(outer) electrons (1) OR, isotopes have the same electron
configuration / same number of e–

(iii) 23/6.023 × 1023 (1)

CE = 0 if inverted or multiplied

tied to M1 3.8(2) × 10–23 [2-5 sig figs] (1)

(b) 1s2 2s2 2p6 3s1 (1)

accept subscripted figures
1

(c) Highest energy e– / outer e–s / last e– in (3)d sub-shell (1)

OR d sub-shell being filled / is incomplete
OR highest energy sub-shell is (3)d
NOT transition element / e– configuration ends at 3d
Q of L
1

(d) N correct symbol (1)

allow

Mass number = 15 AND atomic number = 7 (1)

2
[9]

Q39.
(a) Proton: mass 1, charge + 1 (1)
Neutron: mass 1, charge 0 (1)
Electron mass 1/1840, charge -1 (1)
Allow mass = 0, or negligible, or 1/1800 to 1/2000

Isotopes have the same number of protons (1)

OR atomic number

different number of neutrons (1)

Isotopes have the same electronic configuration (1)

OR same number of electrons

Chemical properties depend on electrons (1)

(b) ×12 (1)

OR × 12 or in words

Spectrum gives (relative) abundance (1)

OR % or amount

Page 78 of 86
And m/z (1)
Multiply m/z by relative abundance for each isotope (1)
Allow instead of m/z mass no, Ar or actual value from
example

Sum these values (1)

Divide by the sum of the relative abundances (1)
only award this mark if previous 2 given
Max 2 if e.g. has only 2 isotopes
7
[14]

Q40.
D
[1]

Page 79 of 86
Examiner reports

Q1.
(a) This question proved demanding for most students. A good number were able to
calculate the mass of the 79Br+ ion. Very few students realised that most of the
quantities cancelled down during the calculation and took time to calculate the
velocity of the 79Br+ ion in order to then work out the kinetic energy. This velocity was
frequently calculated well but the remaining marks then proved a challenge for
students. Some completed numerous calculation steps only to give a time for the
81
Br+ ion that was the same as the time for the 79Br+ ion.

(b) Only a few students understood that when the ion reaches the detector it gains an
electron, whereas many understood that the size of the current was proportional to
the abundance of the ion.

Q2.
(a) Most students (56.1%) could name compound A correctly.

(b) This question proved to be demanding. The calculation of the Mr of individual

molecules containing different isotopes was a challenge for many students. 61.8%
of students either failed to score or made no attempt; 33.4% did, however, score
both marks.

(c) The nucleophilic substitution mechanism was well-answered; 45.6% of students

scored full marks here.

(d) The elimination mechanism was more challenging, and many students did not know
the role of the hydroxide ion. This question discriminated particularly well.

(e) Just under half of students could determine that the IR spectrum was of an alkene
rather than an alcohol and explain this by reference to the absorption for a bond and
its wavenumber range.

(f) Students struggled to explain the relative rates of reaction of the halogenoalkanes.
The most common answer incorrectly referred to the reactivity of the elements
bromine and chlorine, rather than looking at the C-Br and C-Cl bond strengths. Only
28.6% of students gained this mark.

Q3.
The most common answer, C, was incorrect. Students believed that 500 cm3 of water
should be added to the 10 cm3 of solution, rather than adding 490 cm3 to make the total
volume 500 cm3.

Q4.
(a) The electron configuration was well known (88.9% correct).

(b) Only the best students gained both marks here (19%); many students focused on
whether the electron was being removed from a full or partially full orbital instead of
considering why the attraction between the nucleus and the electron might be
different.

Page 80 of 86
was a common error.

(d) The majority of students (76.3%) answered this correctly, although there were quite
a number who gave the incorrect formula.

(e) The ionic equation was generally correct and many students could also calculate
that barium chloride was in excess. Just under a third of students managed to score
all three marks.

(f) Most students could state why isotopes have the same chemical properties. In the
calculation, many students gave an algebraic equation with two unknowns and could
not proceed any further. The students who gave a correct algebraic expression with
one unknown could work through the calculation and generally gained full marks.
Some students answered the question by trial and error and this was also given full
credit. Pleasingly, 43.7% of students gained all four marks available.

(g) Most students deduced that the mass number of the ion would be 138 but less than
30% of students could give the correct formula for the ion including its charge.

(h) Some students answered this part very well (with 36.6% scoring full marks), but
most students scored partial marks or no marks; common errors included failure to
use the Avogadro constant, not converting mass to kg, and incorrect rearrangement
of expressions.

Q5.
(a) This was surprisingly poorly answered. Many students were unable to write the
electronic configuration for Fe2+.

(b) Part (b) was generally well answered, but a significant number of answers had
missing state symbols, despite the direct instruction to include them.

(c) Part (c) was quite well answered.

(d) The symbol including mass number was often incorrect. The calculation of A r was
straightforward and done well by many students.

Q6.
48.5% of students scored this mark; the most common wrong answer was D, showing that
some students thought that a magnetic field is involved in TOF mass spectrometry.

Q7.
Only 26.2% of students selected the correct answer here, with all three distractors
attracting significant numbers of students. Although this example is commonly taught,
there are clearly not many students who can either remember the example or work out the
probabilities for themselves.

Q8.
(a) This was generally well answered, though a few students added the abundances
incorrectly.

(b) Most students gave the correct equation, but some used the wrong state symbols or
omitted them. The identity of the isotope was well known but some students lost a
mark by using the symbol for the atom rather than the m/z value.

Page 81 of 86
(c) The most common error was a failure to convert from grams into kilograms.

(d) Only the best students gained all three marks. All marks were available, even for
those students who had not answered part (c), or who had the wrong answer for it.
Some students were unable to re-arrange the equation. Students who appreciated
that the distance travelled was common to both ions usually went on to get the
correct answer, but a large number of students scored zero or one mark.

Q17.
Aspects of this question were well done but significant numbers were unable to write the
electronic configuration of the Cr3+ ion. part (b) was answered well but the unfamiliar
formula required in (c) proved tricky for the majority.

Q18.
For Question (a) many students wrote a lot of unnecessary detail about aspects of a time
of flight mass spectrometer but on the whole it was quite well answered. Questions (b)
and (c) proved mathematically difficult for many although consequential marking allowed
large numbers to score on (c). The use of probability to predict the ratio of peaks in
question (d) proved very difficult for students. Some scored 1 mark for giving three peaks
but the 1:2:1 ratio was only seen from 11.3% of students. Question (e) was answered well
with over 60% of students scoring all 4 marks.

Q21.
Students found part (a) tricky and many did not realise the significance of the [Kr] given;
however some students answered very well and had all the sublevels in the correct order.
Part (b)(i) was answered very well by most students. Common mistakes included failed
attempts to express the data as percentages and not giving the answer to the required
number of decimal places. There were many confused answers to part (d)(ii) and these
included references to impurities and the size of the sample rather than the fact that the
Periodic Table takes into account all isotopes whereas the sample didn’t. The equation in
part (c) was often given the wrong way round showing that students did not understand
the process occurring at the detector; many students used Tl rather than Te in their
equations. In part (e) the majority of students chose the correct answer and gave a good
explanation of their choice. The most common error was choosing 130 and stating that it
had the biggest value. Many students thought that the atomic radius of the two isotopes in
part (f) was the same but did not then give a complete explanation; many only referred to
the number of protons in the nucleus.

Q22.
The overall performance in part (a)(i) was disappointing because many students did not
know the subatomic particles in the hydrogen atom. The mark in part (a)(ii) was scored by
most students. Many students scored both marks in part (b)(i) but several quoted an
equation involving x and y but could not progress beyond that. The majority of students
answered part (b)(ii) correctly and part (c) was also generally well done. In part (d), many
students used Br instead of B in their equation and some either wrote the wrong ionisation
energy or failed to add state symbols. Many answers to part (e) were superficial; many
students simply referred to a different proton / electron ratio or the removal of an electron
from a different energy level.

Q23.
The definition in part (a) is still not well known. Average or mean was often omitted as was

Page 82 of 86
mass. Part (b) was well done although a few students still chose to divide by 100. In part
(c), the charge on the ion was often missed out. The most common wrong answer in part
(d) was 74 since students were obviously confusing deflection with detection. The majority
who chose 70 carried on to give the correct explanation. Answers to part (e) were poor
with many students not referring to electrons at all. Most students scored the mark in part
(f).

Q24.
In part (a), a significant number of students struggled with a definition of mass number
and many defined Ar instead. The majority of students could answer part (b) well. The
answers to part (c)(i) were well known although many students gave too much detail. In
some cases, this extra detail was contradictory and, therefore, lost the marks. In part (c)
(ii), weaker students thought that mass and charge could be recorded separately. Answers
to part (d) were generally good although many failed to read the instruction to quote the
answer to 1 decimal place. Answers to part (d)(iii) were generally good although there
were many irrelevant references to protons. Weaker students simply quoted that electrons
determine chemical properties but did not refer to the isotopes of R.

Q25.
Part (a) was done very well. In part (b)(i), many students stated that a positive ion was
formed but failed to say how. The equation in part (b)(ii) was well done with only a few
omitting the state symbols. In part (c), a number of students failed to score the mark since
they referred to a rubidium molecule, showing a lack of understanding of the metals given.
In part (d)(ii) there were many students who filled the 4d rather than the 5s orbitals and
some gave an abbreviated electron structure even though the question asked for the full
electron structure. Many students found part (e) difficult although it was pleasing to see
some gain full marks. Part (f) was not well understood with many students confusing
charge and current. The answers to part (g) were generally good although a few students
did not give complete explanations and lost the last mark.

Q26.
Balancing the equation in part (a) taxed some students but most were able to score at
least one mark in part (b). There was a need for students to use correct chemical
terminology in part (d), requiring, for example, reference to the “addition of water” in part
(d)(ii). It was surprising to see how many made simple errors in the relatively
straightforward part (d)(iii), for example, naming the alcohol as propanol rather than
propan–2–ol.

Q27.
The majority of students calculated the relative atomic mass of krypton but then failed to
quote their answer to the precision stated in the question. The last mark in part (a) proved
more difficult with many students suggesting errors in measurements or precision. Part (b)
gave a good spread of marks. The first three marks were gained by most students but
some failed to give state symbols in their equation. The last two marks were more difficult
and many references to the atom being split in two were seen rather than being ionised
twice.

Q28.
Part (a)(i) was well done although many candidates gave a lot of unnecessary extra
information about protons and electrons. In part (a)(ii) there were quite a lot of answers
which simply stated that a variation in neutron number had no effect on chemical

Page 83 of 86
properties; this approach was not an answer to the question. Answers to part (b) showed
that some candidates fail to learn definitions accurately. In part (c)(i) several candidates
divided by 100 rather than by 27 and a few failed to give their answer to one decimal
place. There were very few correct answers to part (c)(ii). Even when zinc was identified
the + sign was often missed. The most common incorrect answer was copper. Part (d)
was well done but part (e) was not well understood. Electric charge was often mentioned
and many thought that positive ions flowed into the computer.

Q29.
Generally well done by a large number of candidates. However the definition of mass
number was often confused with relative atomic mass and a surprising number did not
state the correct numbers of protons, neutrons and electrons.

Q30.
Answers to the definition in part (a) were variable as always. The most common errors
were to miss out the word average/mean on the top line and 1 atom on the bottom line.
The calculation was attempted well although some candidates did not give their answer to
2 decimal places. Part (b) was generally well answered. Part (c) answers were varied.
Some candidates thought that natural and synthetic compounds would react differently
and the ones who knew the reactions were identical often failed to qualify their answer
sufficiently well to gain full maks.

Q31.
Few candidates could not make some progress in the empirical formula calculation in this
part (a), but many were unable to deduce a Mr value from the spectrum in this part (b).
The provision of dummy data in this part (c) allowed most candidates to score at least one
of the marks.

Q32.
A substantial number of candidates were not able to produce an exact definition in part
(a). Many marks were lost through the omission of vital words such as “mass” or “atom”,
or mixing moles and atoms in their answer.

Part (b) was moderately well done but many candidates identified the element rather than
the block it was in. The electron configuration was generally well known with the
commonest errors being [Ar] 4s2 4d2 and 3d4. A significant number of candidates could not
calculate the number of neutrons and many gave non-integer answers such as 25.9.

In part (c) many candidates were able to calculate the relative atomic mass correctly but
did not then identify the element. Weaker candidates included 93 × 0 = 93 in their
calculation or divided by 100. A small number used 91.2 as the atomic number and
therefore identified protactinium.

The great majority of candidates scored the first 2 marks in part (d). However, many did
not actually identify the isotope, often merely stating that it would be the lightest that would
be deflected the most. A disappointing number misinterpreted the mass spectrum and
selected 91 because it had the least abundance. A surprising number wrote that the
heaviest ions would be deflected the most.

Part (e) was not well answered. Although many candidates knew that detection of ions
involved the production of a current, relatively few mentioned the relationship between the
size of current and the abundance of ion. Common incomplete answers included “the

Page 84 of 86
more ions that hit the detector, the greater the abundance”. A very small number of
candidates thought a current was produced by the ion giving electrons to the detector.

Q33.
In part (a) the majority of the candidates scored full marks with some losing marks by
referring to a charge of + rather then +1, or putting a + (plus) or a – (minus) sign in the
relative mass column. The answer to part (b) was well done with only a few writing
‘Transition metals’ rather than stating the block that tungsten is in. Some candidates did
not score marks in part (c) since they did not look for the atomic number in the Periodic
Table and some could not remember how to calculate the number of neutrons. Candidates
generally answered part (d) well although a few put ‘detect’ as one of their answers and
this was given in the stem of the question. Some tried to explain how the ions were
formed but this was not asked for. Part d (ii) was well answered. In part (e) candidates lost
the second mark by not knowing that the isotopes have the same electron configuration.
Many answers just stated that isotopes had different numbers of neutrons and/or same
number of protons. The calculation in part (f) was very well done although some
candidates lost the second mark by not giving their answer to two decimal places.

Q35.
On the whole, this question was well answered. The relative masses and charges of
neutrons and electrons were generally well known but errors were not uncommon. Some
candidates reversed the contents of the mass and charge columns, suggesting that they
had rote learned a table with a different layout of columns.

Part (b) was quite well done but errors such as 17Be, 13O, 17.0O and 16O were not
uncommon.

While many candidates correctly deduced the shapes of the molecules in part (c), the
presence of a lone pair of electrons on the Be atom, or one/three lone pairs of electrons
on the O atom, was quite common. The shape of the BeCl2 molecule was well known but
there was considerable confusion regarding the shape of the Cl2O molecule. Many
candidates gave tetrahedral as the shape of this molecule. While the distribution of
electron pairs around the oxygen atom might be described as tetrahedral, this is not the
shape produced by the atoms in the molecule. Many candidates described the shape in
appropriately by using the terms bent, V-shaped and angular. The use of tetrahedral was
accepted in this examination but this may not be the case in future examinations. A
significant number of candidates used the term bent linear when describing the shape of
Cl2O molecules; this was treated as a contradiction and so earned no credit. A significant
number of candidates attempted to show the shapes of these molecules using dot-and-
cross diagrams; these were not accepted.

The calculation in part (d) was correctly performed by many candidates, but errors such
as the use of incorrect Mr values or the use of an incorrect mole ratio were quite common.
A small but significant number of candidates assumed the use of a known mass of HCl
and ignore the 1.00 g of Mg(OH)2 stipulated in the question; such answered earned no
credit.

Q37.
The fundamental particle data required in part (a) was generally well known; however,
relative charges where either the sign or the value was omitted were occasionally seen.
Part (b)(i) was well answered, and the majority of candidates coped well with (b)(ii). It was
quite common however to see 28.1, rather than the required 28, to be quoted as the mass
number of Q. Part (c) simply required a standard definition for the Ar to be quoted.
Surprisingly, this question was quite poorly done, with attempts being frequently vague

Page 85 of 86
and incomplete. The most common error was to omit references to mean, mass and
atoms in the definition. Also, it was not uncommon to see a ratio showing single atoms on
the top and moles on the bottom. In part (d), the calculation of the Ar of the sample of
magnesium was usually correct, however, a significant number of candidates failed to
quote their final answer to one decimal place. Some candidates used the sum of the m/z
values, rather than the sum of the relative abundances (100). Part (e) was very poorly
answered. Very few references to highest m/z value were seen.

Q38.
Many good answers were seen here and high marks were quite common. However,
candidates frequently ignored the instruction in (a)(i) to define isotopes in terms of
fundamental particles, and offered a definition based wholly, or in part, on mass number
and atomic number. In (a)(ii), the link between chemical properties and electron
configuration was well known but many candidates attempted to establish a link between
proton, neutron or mass numbers and chemical properties. The calculation in (a)(iii) was
often poorly done, the most common errors being to invert the expression or to multiply
the mass number by L. Part (b) was generally well answered, although a few candidates
gave the electron arrangement showing 23 electrons. Similarly, part (c) was generally well
answered, however, some candidates referred to electrons being in the d block, while a
small minority offered nonsense explanations. Most candidates correctly identified
nitrogen as the element in part (d), but was a common error.

Q39.
Most candidates scored high marks for part (a) though the final part of the question,
requiring an explanation why isotopes have identical chemical properties, was more
demanding. Part (b) was also answered well though a considerable number of candidates
wasted time by giving detailed but irrelevant information about the operation of the various
parts of a mass spectrometer. Candidates were often imprecise about the information that
can be obtained from a mass spectrum. Confusion between mass/charge and atomic
mass or relative atomic mass was common but did not incur a heavy penalty.

Page 86 of 86

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