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General Certificate of Education

January 2007
Advanced Subsidiary Examination

CHEMISTRY CHM1
Unit 1 Atomic Structure, Bonding and Periodicity

Thursday 11 January 2007 9.00 am to 10.00 am

For this paper you must have For Examiner’s Use

● a calculator.

Question Mark Question Mark

Time allowed: 1 hour 1

Instructions 2
● Use blue or black ink or ball-point pen.

● Fill in the boxes at the top of this page.

3
● Answer all questions.
4
● Answer the questions in Section A and Section B in the spaces

provided. 5
● All working must be shown.

● Do all rough work in this book. Cross through any work you do not 6
want to be marked.
● The Periodic Table/Data Sheet is provided on pages 3 and 4. Detach

this perforated sheet at the start of the examination.

Information
Total (Column 1) →
● The maximum mark for this paper is 60.

● The marks for questions are shown in brackets. Total (Column 2) →

● You are expected to use a calculator where appropriate.

● Write your answers to the questions in Section B in continuous prose, TOTAL

where appropriate. You will be assessed on your ability to use an

appropriate form and style of writing, to organise relevant information Examiner’s Initials

clearly and coherently, and to use specialist vocabulary, where

appropriate.

Advice
● You are advised to spend about 45 minutes on Section A and about

15 minutes on Section B.

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SECTION A

Answer all questions in the spaces provided.

1 (a) Complete the following table.

Relative mass Relative charge

Proton

Electron
(2 marks)

(b) An atom has twice as many protons and twice as many neutrons as an atom of 19F
Deduce the symbol, including the mass number, of this atom.

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(2 marks)

(c) The Al3+ ion and the Na+ ion have the same electron arrangement.

(i) Give the electron arrangement of these ions.

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(ii) Explain why more energy is needed to remove an electron from the Al3+ ion than
from the Na+ ion.

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(3 marks)

(d) In a mass spectrometer, gaseous atoms are ionised. These ions are then accelerated.

(i) Explain how atoms are ionised in a mass spectrometer.

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 The Periodic Table of the Elements
■ The atomic numbers and approximate relative atomic masses shown in the table are for use in the examination unless stated
otherwise in an individual question.

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I II III IV V VI VII 0
1.0 4.0
H He
Hydrogen
Key Helium
1 2
6.9 9.0 relative atomic mass 6.9 10.8 12.0 14.0 16.0 19.0 20.2
Li Be Li B C N O F Ne
Lithium Beryllium Lithium Boron Carbon Nitrogen Oxygen Fluorine Neon
3 4 atomic number 3 5 6 7 8 9 10
23.0 24.3 27.0 28.1 31.0 32.1 35.5 39.9
Na Mg Al Si P S Cl Ar
Sodium Magnesium Aluminium Silicon Phosphorus Sulphur Chlorine Argon
11 12 13 14 15 16 17 18
39.1 40.1 45.0 47.9 50.9 52.0 54.9 55.8 58.9 58.7 63.5 65.4 69.7 72.6 74.9 79.0 79.9 83.8
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
3

19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
85.5 87.6 88.9 91.2 92.9 95.9 98.9 101.1 102.9 106.4 107.9 112.4 114.8 118.7 121.8 127.6 126.9 131.3
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54
132.9 137.3 138.9 178.5 180.9 183.9 186.2 190.2 192.2 195.1 197.0 200.6 204.4 207.2 209.0 210.0 210.0 222.0
Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Caesium Barium Lanthanum Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury Thallium Lead Bismuth Polonium Astatine Radon
55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86
*
223.0 226.0 227
Fr Ra Ac
Francium Radium Actinium
87 88 89 †

140.1 140.9 144.2 144.9 150.4 152.0 157.3 158.9 162.5 164.9 167.3 168.9 173.0 175.0
Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
* 58 – 71 Lanthanides Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium
58 59 60 61 62 63 64 65 66 67 68 69 70 71
232.0 231.0 238.0 237.0 239.1 243.1 247.1 247.1 252.1 (252) (257) (258) (259) (260)
Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
† 90 – 103 Actinides Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium
90 91 92 93 94 95 96 97 98 99 100 101 102 103
 4

Gas constant R = 8.31 J K–1 mol–1

Table 1
Proton n.m.r chemical shift data

Type of proton δ/ppm

RCH3 0.7–1.2
R2CH2 1.2–1.4
R3CH 1.4–1.6
RCOCH3 2.1–2.6
ROCH3 3.1–3.9
RCOOCH3 3.7–4.1
ROH 0.5–5.0

Table 2
Infra-red absorption data

Bond Wavenumber/cm–1

C—H 2850–3300
C—C 750–1100
C C 1620–1680
C O 1680–1750
C—O 1000–1300
O—H (alcohols) 3230–3550
O—H (acids) 2500–3000

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(ii) State what is used to accelerate ions in a mass spectrometer.

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(3 marks)

(e) The table below shows the relative abundance of each isotope in a sample of platinum.

m/z 194 195 196 198

Relative abundance (%) 32.8 30.6 25.4 11.2

Use the data in the table to calculate the relative atomic mass of this sample of
platinum.
Give your answer to one decimal place.

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(2 marks)

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2 (a) An acid, H2X, reacts with sodium hydroxide as shown in the equation below.
–
H2X(aq) + 2NaOH(aq) → 2Na+(aq) + X2 (aq) + 2H2O(l)

A solution of this acid was prepared by dissolving 1.92 g of H2X in water and making
the volume up to 250 cm3 in a volumetric flask.

A 25.0 cm3 sample of this solution required 21.70 cm3 of 0.150 mol dm–3 aqueous
NaOH for complete reaction.
–3
(i) Calculate the number of moles of NaOH in 21.70 cm3 of 0.150 mol dm aqueous
NaOH

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(ii) Calculate the number of moles of H2X which reacted with this amount of NaOH
Hence, deduce the number of moles of H2X in the 1.92 g sample.

Moles of H2X in 25.0 cm3 of solution .......................................................................

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Moles of H2X in 1.92 g sample .................................................................................

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(iii) Calculate the relative molecular mass, Mr, of H2X

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(5 marks)

(b) Analysis of a compound Y showed that it contained 49.31 % of carbon, 6.85 % of

hydrogen and 43.84 % of oxygen by mass. The Mr of Y is 146.0

(i) State what is meant by the term empirical formula.

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(ii) Use the above data to calculate the empirical formula and the molecular formula
of Y.

Empirical formula of Y ............................................................................................

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Molecular formula of Y ............................................................................................

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(4 marks)

(c) Sodium hydrogencarbonate decomposes on heating as shown in the equation below.

2NaHCO3(s) → Na2CO3(s) + CO2(g) + H2O(g)

A sample of NaHCO3 was heated until completely decomposed. The CO2 formed in
the reaction occupied a volume of 352 cm3 at 1.00 × 105 Pa and 298 K.

(i) State the ideal gas equation and use it to calculate the number of moles of CO2
formed in this decomposition.
(The gas constant R = 8.31 J K–1 mol–1)

Ideal gas equation ....................................................................................................

Moles of CO2 ............................................................................................................

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(ii) Use your answer from part (c)(i) to calculate the mass of the NaHCO3 that has
decomposed.
(If you have been unable to calculate the number of moles of CO2 in part (c)(i),
you should assume this to be 0.0230 mol. This is not the correct value.)

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(7 marks)

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3 (a) (i) State what is meant by the term polar when applied to a covalent bond.

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(ii) Consider the covalent bonds in molecules of hydrogen and of water. State
whether the covalent bonds are polar or non-polar. Explain your answers.

Bonds in hydrogen ....................................................................................................

Bonds in water ..........................................................................................................

Explanation ..............................................................................................................

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(4 marks)

(b) Ammonia is very soluble in water because it is able to form hydrogen bonds with
water molecules.

(i) Complete the diagram below to show how an ammonia molecule forms a
hydrogen bond with a water molecule. Include partial charges and all the lone
pairs of electrons.

H
N H O
H
H H

(ii) The bond angle in a molecule of water is about 104.5°. State the bond angle in
an ammonia molecule and explain why it is different from that in water.

Bond angle in ammonia ...........................................................................................

Explanation ..............................................................................................................

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(6 marks)

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(c) Ammonia reacts with aluminium chloride to form the molecule shown below.

H Cl
N Al
H Cl
H Cl

Name the type of bond formed between the nitrogen and aluminium atoms. Explain
how this bond is formed.

Type of bond .......................................................................................................................

Explanation ........................................................................................................................

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(2 marks)

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4 (a) Give the formula of the least soluble hydroxide of the Group II elements Mg to Ba.

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(1 mark)

(b) An aqueous solution of sodium chloride may be distinguished from an aqueous

solution of sodium sulphate using a simple chemical test.

(i) Identify a reagent for this test.

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(ii) State the observations you would expect to make if the reagent identified
in part (b)(i) is added to a separate sample of each solution. Write an equation
for any reaction which occurs.

Observation with sodium chloride ...........................................................................

Observation with sodium sulphate ...........................................................................

Equation ...................................................................................................................

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(4 marks)

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SECTION B

Answer both questions in the spaces provided.

5 Draw a diagram to show how the ions are arranged in three dimensions in a crystal of
sodium chloride. Explain, in terms of bonding, why sodium chloride has a high melting
point. State and explain a condition needed for sodium chloride to conduct electricity.
(6 marks)

6 (a) State and explain the trend in atomic radius of the elements Na to Cl in Period 3.
(4 marks)

(b) State the meaning of the term first ionisation energy of an atom.
State the general trend in the first ionisation energy of the Period 3 elements Na to Ar.
Identify and explain one deviation from this general trend.
(5 marks)

END OF QUESTIONS

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APW/Jan07/CHM1