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Chemistry Exam: Molecular Shapes & Bonds

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0% found this document useful (0 votes)

13 views71 pages

Chemistry Exam: Molecular Shapes & Bonds

fdsf ds ds ds ds ds

Uploaded by

zayanarshad.08

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

Available Formats

Download as PDF, TXT or read online on Scribd

You are on page 1/ 71

Ammonia reacts with aluminium chloride as shown by the equation:

1
NH3 + AlCl3 → H3NAlCl3

(a) Draw diagrams to illustrate the shapes of NH3 molecules and of AlCl3 molecules.

Include in your diagrams any lone pairs of electrons that influence the shape.

Indicate the values of the bond angles.

(3)

(b) Name the type of bond formed between N and Al in H3NAlCl3 and explain how this bond is
formed.

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

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

.............................................................................................................................

.............................................................................................................................
(2)

Page 1 of 71
(c) Explain how the value of the Cl-Al-Cl bond angle in AlCl3 changes, if at all, on formation of
the compound H3NAlCl3

.............................................................................................................................

.............................................................................................................................
(2)
(Total 7 marks)

(a) Write an equation, including state symbols, for the reaction with enthalpy change
2 equal to the standard enthalpy of formation for CF4(g).

........................................................................................................................
(1)

(b) Explain why CF4 has a bond angle of 109.5°.

........................................................................................................................

........................................................................................................................
(2)

Page 2 of 71
(c) Table 1 gives some values of standard enthalpies of formation (ΔfHϴ).

Table 1

Substance F2(g) CF4(g) HF(g)

ΔfHϴ / kJ mol−1 0 −680 −269

The enthalpy change for the following reaction is −2889 kJ mol−1.

C2H6(g) + 7F2(g) 2CF4(g) + 6HF(g)

Use this value and the standard enthalpies of formation in Table 1 to calculate the standard
enthalpy of formation of C2H6(g).

Standard enthalpy of formation of C2H6(g) = .................... kJ mol−1

(3)

Page 3 of 71
(d) Methane reacts violently with fluorine according to the following equation.

CH4(g) + 4F2(g) CF4(g) + 4HF(g) ΔH = −1904 kJ mol−1

Some mean bond enthalpies are given in Table 2.

Table 2

Bond C−H C−F H−F

Mean bond enthalpy / kJ mol−1 412 484 562

A student suggested that one reason for the high reactivity of fluorine is a weak F−F bond.

Is the student correct? Justify your answer with a calculation using these data.

........................................................................................................................

........................................................................................................................
(4)
(Total 10 marks)

Which of these species has a trigonal planar structure?

3
A PH3

B BCl3

C H3O+

D CH3−

(Total 1 mark)

Page 4 of 71
(a) Explain how the electron pair repulsion theory can be used to deduce the shape of, and the
4 bond angle in, PF3

........................................................................................................................

........................................................................................................................
(6)

(b) State the full electron configuration of a cobalt(II) ion.

........................................................................................................................
(1)

........................................................................................................................

........................................................................................................................
(1)

(d) Predict the shape of, and the bond angle in, the complex rhodium ion [RhCl4]2−.

Shape ............................................................................................................

Bond angle .....................................................................................................

(2)
(Total 10 marks)

Page 5 of 71
This question is about the elements in Period 3 of the Periodic Table.
5
(a) State the element in Period 3 that has the highest melting point.
Explain your answer.

Element ..........................................................................................................

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

........................................................................................................................

........................................................................................................................
(3)

(b) State the element in Period 3 that has the highest first ionisation energy.
Explain your answer.

Element ..........................................................................................................

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

........................................................................................................................

........................................................................................................................
(3)

........................................................................................................................
(1)

(d) Chlorine is a Period 3 element.

Chlorine forms the molecules ClF3 and CCl2

(i) Use your understanding of electron pair repulsion to draw the shape of ClF3 and the
shape of CCl2
Include any lone pairs of electrons that influence the shape.

Shape of ClF3 Shape of CCl2

(2)

(ii) Name the shape of CCl2

...............................................................................................................
(1)

Page 6 of 71
(iii) Write an equation to show the formation of one mole of ClF3 from its elements.

...............................................................................................................
(1)
(Total 11 marks)

A hydrogen peroxide molecule can be represented by the structure shown.

(a) Suggest a value for the H−O−O bond angle.

........................................................................................................................
(1)

(b) Hydrogen peroxide dissolves in water.

(i) State the strongest type of interaction that occurs between molecules of hydrogen
peroxide and water.

...............................................................................................................
(1)

(ii) Draw a diagram to show how one molecule of hydrogen peroxide interacts with one
molecule of water.
Include all lone pairs and partial charges in your diagram.

(3)

Page 7 of 71
(c) Explain, in terms of electronegativity, why the boiling point of H2S2 is lower than H2O2.

........................................................................................................................

........................................................................................................................
(2)
(Total 7 marks)

Thallium is in Group 3 of the Periodic Table.

7 Thallium reacts with halogens to form many compounds and ions.

(a) Draw the shape of the TlBr32– ion and the shape of the TlCl43– ion.
Include any lone pairs of electrons that influence the shapes.

Name the shape made by the atoms in TlBr32– and suggest a value for the bond angle.

........................................................................................................................
(4)

(b) Thallium(I) bromide (TlBr) is a crystalline solid with a melting point of 480 °C.

Suggest the type of bonding present in thallium(I) bromide and state why the melting point
is high.

........................................................................................................................

........................................................................................................................
(3)

Page 8 of 71
(c) Write an equation to show the formation of thallium(I) bromide from its elements.

........................................................................................................................
(1)
(Total 8 marks)

Aluminium and thallium are elements in Group 3 of the Periodic Table.

8 Both elements form compounds and ions containing chlorine and bromine.

(a) Write an equation for the formation of aluminium chloride from its elements.

........................................................................................................................
(1)

(b) An aluminium chloride molecule reacts with a chloride ion to form the AlCl4− ion.

Name the type of bond formed in this reaction. Explain how this type of bond is formed in
the AlCl4− ion.

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

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

........................................................................................................................

........................................................................................................................
(2)

Deduce the formula of the aluminium compound that has a relative molecular mass of 267

........................................................................................................................
(1)

(d) Deduce the name or formula of a compound that has the same number of atoms, the same
number of electrons and the same shape as the AlCl4− ion.

........................................................................................................................
(1)

(e) Draw and name the shape of the TlBr52− ion.

Shape of the TlBr52− ion.

Name of shape ..............................................................................................

(2)

Page 9 of 71
(f) (i) Draw the shape of the TlCl2+ ion.

(1)

(ii) Explain why the TlCl2+ ion has the shape that you have drawn in part (f)(i).

........................................................................................................................

........................................................................................................................
(1)

(g) Which one of the first, second or third ionisations of thallium produces an ion with the
electron configuration [Xe] 5d106s1?

Tick ( ) one box.

First

Second

Third

(1)
(Total 10 marks)

Page 10 of 71
Chlorine can form molecules and ions that contain only chlorine, or that contain chlorine
9 combined with another element.

(a) Use your understanding of the electron pair repulsion theory to draw the shape of the AsCl3
molecule and the shape of the Cl3+ ion.
Include any lone pairs of electrons that influence the shape.

Name the shape made by the atoms in the AsCl3 molecule and in the Cl3+ ion.

........................................................................................................................

(Extra space) .................................................................................................

........................................................................................................................
(4)

(b) Explain why the AsCl4+ ion has a bond angle of 109.5°.

........................................................................................................................

(Extra space)..................................................................................................

........................................................................................................................
(2)
(Total 6 marks)

Page 11 of 71
The following equation shows the reaction of a phosphine molecule (PH3) with an H+ ion.
10
PH3 + H+ PH4+

(a) Draw the shape of the PH3 molecule. Include any lone pairs of electrons that influence the
shape.

(1)

(b) State the type of bond that is formed between the PH3 molecule and the H+ ion.
Explain how this bond is formed.

Name of bond ................................................................................................

How bond is formed ......................................................................................

........................................................................................................................
(2)

(c) Predict the bond angle in the PH4 + ion.

........................................................................................................................
(1)

(d) Although phosphine molecules contain hydrogen atoms, there is no hydrogen bonding
between phosphine molecules.
Suggest an explanation for this.

........................................................................................................................

........................................................................................................................
(1)
(Total 5 marks)

Page 12 of 71
(a) Boron trichloride (BCl3) can be prepared as shown by the following equation.
11
B2O3(s) + 3C(s) + 3Cl2(g) 2BCl3(g) + 3CO(g)

A sample of boron oxide (B2O3) was reacted completely with carbon and chlorine.
The two gases produced occupied a total volume of 5000 cm3 at a pressure of 100 kPa and
a temperature of 298 K.

Calculate the mass of boron oxide that reacted.

Give your answer to 3 significant figures.

(The gas constant R = 8.31 J K–1 mol–1)

........................................................................................................................

(Extra space) .................................................................................................

........................................................................................................................

........................................................................................................................
(5)

Page 13 of 71
(b) Boron trichloride can also be prepared from its elements.

Write an equation for this reaction.

Explain why boron trichloride has a trigonal planar shape with equal bond angles.

........................................................................................................................

(Extra space) .................................................................................................

........................................................................................................................
(3)

BCl3(g) + 3H2O(I) H3BO3(aq) + 3HCl(aq)

Calculate the concentration, in mol dm–3, of hydrochloric acid produced when 43.2 g
of boron trichloride are added to water to form 500 cm3 of solution.
Give your answer to 3 significant figures.

...............................................................................................................

(Extra space) ........................................................................................

...............................................................................................................
(4)

Page 14 of 71
(ii) Boric acid (H3BO3) can react with sodium hydroxide to form sodium borate and water.
Write an equation for this reaction.

...............................................................................................................
(1)

(d) Boron trichloride can be reduced by using hydrogen to form pure boron.

BCl3(g) + 1 H2(g) B(s) + 3HCl(g)

Calculate the percentage atom economy for the formation of boron in this reaction.

Apart from changing the reaction conditions, suggest one way a company producing pure
boron could increase its profits from this reaction.

........................................................................................................................

(Extra space) .................................................................................................

........................................................................................................................
(3)

Page 15 of 71
(e) A different compound of boron and chlorine has a relative molecular mass of 163.6 and
contains 13.2% of boron by mass.

Calculate the molecular formula of this compound.

Show your working.

........................................................................................................................

(Extra space) .................................................................................................

........................................................................................................................
(4)
(Total 20 marks)

Fluorine forms compounds with many other elements.

12
(a) Fluorine reacts with bromine to form liquid bromine trifluoride (BrF3).
State the type of bond between Br and F in BrF3 and state how this bond is formed.

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

How bond is formed ......................................................................................

........................................................................................................................
(2)

Page 16 of 71
(b) Two molecules of BrF3 react to form ions as shown by the following equation.

2BrF3 BrF2+ + BrF4–

(i) Draw the shape of BrF3 and predict its bond angle.
Include any lone pairs of electrons that influence the shape.

Shape of BrF3

Bond angle ............................................................................................

(2)

(ii) Draw the shape of BrF4– and predict its bond angle.
Include any lone pairs of electrons that influence the shape.

Shape of BrF4–

Bond angle ............................................................................................

(2)

(c) BrF4– ions are also formed when potassium fluoride dissolves in liquid BrF3 to form KBrF4
Explain, in terms of bonding, why KBrF4 has a high melting point.

........................................................................................................................

(Extra space) .................................................................................................

........................................................................................................................
(3)

Page 17 of 71
(d) Fluorine reacts with hydrogen to form hydrogen fluoride (HF).

(i) State the strongest type of intermolecular force between hydrogen fluoride molecules.

...............................................................................................................
(1)

(ii) Draw a diagram to show how two molecules of hydrogen fluoride are attracted to
each other by the type of intermolecular force that you stated in part (d)(i). Include all
partial charges and all lone pairs of electrons in your diagram.

(3)

(e) The boiling points of fluorine and hydrogen fluoride are –188 °C and 19.5 °C respectively.
Explain, in terms of bonding, why the boiling point of fluorine is very low.

........................................................................................................................

(Extra space) .................................................................................................

........................................................................................................................
(2)
(Total 15 marks)

Fluorine and iodine are elements in Group 7 of the Periodic Table.

13
(a) Explain why iodine has a higher melting point than fluorine.

......................................................................................................................

(Extra space)................................................................................................

......................................................................................................................
(2)

Page 18 of 71
(b) (i) Draw the shape of the NHF2 molecule and the shape of the BF3 molecule.

Include any lone pairs of electrons that influence the shape. In each case name the
shape.

Shape of NHF2 Shape of BF3

Name of shape of NHF2 .....................................................................

Name of shape of BF3 ........................................................................

(4)

(ii) Suggest a value for the F—N—F bond angle in NHF

.............................................................................................................
(1)

(c) State the strongest type of intermolecular force in a sample of NHF2

......................................................................................................................
(1)

(d) A molecule of NHF2 reacts with a molecule of BF3 as shown in the following equation.

NHF2 + BF3 F2HNBF3

State the type of bond formed between the N atom and the B atom in F2HNBF3.

Explain how this bond is formed.

Name of type of bond ..................................................................................

How bond is formed .....................................................................................

......................................................................................................................

......................................................................................................................
(2)
(Total 10 marks)

Page 19 of 71
Water can be found as ice, water and steam.
14
(a) The following diagram shows the arrangement of some of the water molecules in a crystal
of ice.

With reference to the structure shown above give one reason why ice is less dense than
water.

......................................................................................................................

......................................................................................................................
(1)

(b) Water and methane have similar relative molecular masses and both contain the element
hydrogen.
The table below gives some information about water and methane.

H2O CH4
Mr 18.0 16.0
Melting point / K 273 91

(i) State the strongest type of intermolecular force holding the water molecules together
in the ice crystal.

.............................................................................................................
(1)

Page 20 of 71
(ii) State the strongest type of intermolecular force in methane.

.............................................................................................................
(1)

(iii) Give one reason why the melting point of ice is higher than the melting point of
methane.

.............................................................................................................

.............................................................................................................
(1)

(i) Draw and name the shape of the H3O+ ion. Include any lone pairs of electrons.

Shape of the H3O+ ion

Name of shape ...................................................................................

(2)

(ii) Suggest a value for the bond angle in the H3O+ ion.

.............................................................................................................
(1)

(iii) Identify one molecule with the same number of atoms, the same number of electrons
and the same shape as the H3O+ ion.

.............................................................................................................
(1)

(d) Water can also form the hydroxide ion.

State the number of lone pairs of electrons in the hydroxide ion.

......................................................................................................................
(1)
(Total 9 marks)

Page 21 of 71
Fluorine forms many compounds that contain covalent bonds.
15
(a) (i) State the meaning of the term covalent bond.

.............................................................................................................

.............................................................................................................
(1)

(ii) Write an equation to show the formation of one molecule of ClF3 from chlorine and
fluorine molecules.

.............................................................................................................
(1)

(b) Draw the shape of a dichlorodifluoromethane molecule (CCl2F2) and the shape of a
chlorine trifluoride molecule (ClF3). Include any lone pairs of electrons that influence the
shape.

Shape of CCl2F2 Shape of ClF3

(2)

......................................................................................................................
(1)

(d) BF3 is a covalent molecule that reacts with an F– ion to form a BF4– ion.

(i) Name the type of bond formed when a molecule of BF3 reacts with an F– ion. Explain
how this bond is formed.

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

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

.............................................................................................................

.............................................................................................................
(3)

(ii) State the bond angle in the BF4– ion

.............................................................................................................
(1)
Page 22 of 71
(e) An ultrasound imaging agent has the formula C4F10
It can be made by the reaction of butane and fluorine as shown in the following equation.

C4H10 + 10F2 → C4F10 + 10HF

Calculate the percentage atom economy for the formation of C4F10 in this reaction.
Give your answer to three significant figures.

......................................................................................................................

......................................................................................................................
(2)
(Total 11 marks)

A molecule of ClF3 reacts with a molecule of AsF5 as shown in the following equation.
16
ClF3 + AsF5 → ClF2+ + AsF6–

Use your understanding of electron pair repulsion to draw the shape of the AsF5 molecule and
the shape of the ClF2+ ion. Include any lone pairs of electrons.

Name the shape made by the atoms in the AsF5 molecule and in the ClF2+ ion.

Predict the bond angle in the ClF2+ ion.

...............................................................................................................................

...............................................................................................................................
(Total 5 marks)

Page 23 of 71
(a) Complete the electronic configuration for the sodium ion, Na+
17
ls2 .................................................................................................................
(1)

(b) (i) Write an equation, including state symbols, to represent the process for which the
energy change is the second ionisation energy of sodium.

.............................................................................................................
(2)

(ii) Explain why the second ionisation energy of sodium is greater than the second
ionisation energy of magnesium.

.............................................................................................................

.............................................................................................................
(3)

(iii) An element X in Period 3 of the Periodic Table has the following successive
ionisation energies.

First Second Third Fourth

Ionisation energies / kJ mol–1 577 1820 2740 11600

Deduce the identity of element X.

.............................................................................................................
(1)

Trend ...........................................................................................................

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

......................................................................................................................

......................................................................................................................
(3)

Page 24 of 71
(d) Explain why sodium has a lower melting point than magnesium.

......................................................................................................................

......................................................................................................................
(3)

(e) Sodium reacts with ammonia to form the compound NaNH2 which contains the NH2– ion.
Draw the shape of the NH2– ion, including any lone pairs of electrons.
Name the shape made by the three atoms in the NH2– ion.

Shape of NH2–

Name of shape ............................................................................................

(2)

(f) In terms of its electronic configuration, give one reason why neon does not form
compounds with sodium.

......................................................................................................................
(1)
(Total 16 marks)

Page 25 of 71
The table below shows the electronegativity values of some elements.
18
H C N O

Electronegativity 2.1 2.5 3.0 3.5

(a) State the meaning of the term electronegativity.

......................................................................................................................

......................................................................................................................
(2)

(b) State the strongest type of intermolecular force in the following compounds.

Methane (CH4) .............................................................................................

Ammonia (NH3) ............................................................................................

(2)

(c) Use the values in the table to explain how the strongest type of intermolecular force arises
between two molecules of ammonia.

......................................................................................................................

......................................................................................................................
(3)

(d) Phosphorus is in the same group of the Periodic Table as nitrogen.

A molecule of PH3 reacts with an H+ ion to form a PH4+ ion.
Name the type of bond formed when PH3 reacts with H+ and explain how this bond is
formed.

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

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

......................................................................................................................

......................................................................................................................
(3)

Page 26 of 71
(e) Arsenic is in the same group as nitrogen. It forms the compound AsH3
Draw the shape of an AsH3 molecule, including any lone pairs of electrons. Name the
shape made by its atoms.

Shape

Name of shape ............................................................................................

(2)

(f) The boiling point of AsH3 is –62.5 °C and the boiling point of NH3 is –33.0 °C.
Suggest why the boiling point of AsH3 is lower than that of NH3

......................................................................................................................

......................................................................................................................
(1)

(g) Balance the following equation which shows how AsH3 can be made.

...... AsCl3 + ...... NaBH4 → ...... AsH3 + ...... NaCl + ...... BCl3
(1)
(Total 14 marks)

(a) Describe the bonding in, and the structure of, sodium chloride and ice. In each case draw a
19 diagram showing how each structure can be represented. Explain, by reference to the
types of bonding present, why the melting point of these two compounds is very different.
(12)

(b) Explain how the concept of bonding and non-bonding electron pairs can be used to predict
the shape of, and bond angles in, a molecule of sulfur tetrafluoride, SF4.
Illustrate your answer with a diagram of the structure.
(8)
(Total 20 marks)

Page 27 of 71
The equation below shows the reaction between boron trifluoride and a fluoride ion.
20
BF3 + F– → BF

(i) Draw diagrams to show the shape of the BF3 molecule and the shape of the BF ion. In

each case, name the shape. Account for the shape of the BF ion and state the bond
angle present.

(ii) In terms of the electrons involved, explain how the bond between the BF3 molecule and the
F– ion is formed. Name the type of bond formed in this reaction.
(Total 9 marks)

In which one of the following species is the shape influenced by the presence of one or more
21 lone pairs of electrons?

A NH

B NH

C [CH3NH3]+

D [Co(NH3)6]2+
(Total 1 mark)

(a) Complete the following table.

22
Relative mass Relative charge

Neutron

Electron
(2)

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

......................................................................................................................
(2)

Page 28 of 71
(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)

Phosphorus and nitrogen are in Group V of the Periodic Table and both elements form hydrides.
23
Phosphine, PH3, reacts to form phosphonium ions, , in a similar way to that by which

ammonia, NH3, forms ammonium ions,

(a) Give the name of the type of bond formed when phosphine reacts with an H+ ion. Explain
how this bond is formed.

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

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

......................................................................................................................

......................................................................................................................
(3)

Page 29 of 71
(b) Draw the shapes, including any lone pairs of electrons, of a phosphine molecule and of a
phosphonium ion.
Give the name of the shape of the phosphine molecule and state the bond angle found in
the phosphonium ion.

PH3

Shape of PH3 ........................... Bond angle in ...........................

(4)
(Total 7 marks)

Which one of the following molecules is not planar?

24
A BF3

B NCl3

C C 2H 4

D HCHO
(Total 1 mark)

(a) Ammonia, NH3, reacts with sodium to form sodium amide, NaNH2, and hydrogen.
25
(i) Write an equation for the reaction between ammonia and sodium.

.............................................................................................................

Page 30 of 71
(ii) Draw the shape of an ammonia molecule and that of an amide ion, NH

In each case show any lone pairs of electrons.

NH3 NH

(iii) State the bond angle found in an ammonia molecule.

.............................................................................................................

(iv) Explain why the bond angle in an amide ion is smaller than that in an ammonia
molecule.

.............................................................................................................

.............................................................................................................
(6)

(b) A salt, X, contains 16.2% by mass of magnesium, 18.9% by mass of nitrogen and 64.9%
by mass of oxygen.

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

.............................................................................................................

Page 31 of 71
(ii) Determine the empirical formula of X.

.............................................................................................................

.............................................................................................................
(3)
(Total 9 marks)

Lithium hydride, LiH, is an ionic compound containing the hydride ion, H–

26
The reaction between LiH and aluminium chloride, AlCl3, produces the ionic compound LiAlH4

(a) Balance the equation below which represents the reaction between LiH and AlCl3

LiH + AlCl3 → LiAlH4 + LiCl

(1)

(b) Give the electronic configuration of the hydride ion, H–

......................................................................................................................
(1)

Shape ..........................................................................................................

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

......................................................................................................................

......................................................................................................................
(3)

Page 32 of 71
(d) A bond in can be represented by H → Al

Name this type of bond and explain how it is formed.

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

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

......................................................................................................................

......................................................................................................................
(3)
(Total 8 marks)

(a) Both HF and HCl are molecules having a polar covalent bond. Their boiling points are
27 293 K and 188 K respectively.

(i) State which property of the atoms involved causes a bond to be polar.

.............................................................................................................

(ii) Explain, in terms of the intermolecular forces present in each compound, why HF has
a higher boiling point than HCl.

.............................................................................................................

.............................................................................................................
(4)

(b) When aluminium chloride reacts with chloride ions, as shown by the equation below, a
co-ordinate bond is formed.

AlCl3 + Cl– → AlCl4–

Explain how this co-ordinate bond is formed.

......................................................................................................................

......................................................................................................................
(2)

Page 33 of 71
(c) Draw the shape of the PCl5 molecule and of the PCl4+ ion. State the value(s) of the bond
angles.

PCl5 PCl4+

Bond angle(s) ................................. Bond angle(s) ..................................

(4)
(Total 10 marks)

28 (a) Predict the shapes of the SF6 molecule and the ion. Draw diagrams of these species
to show their three-dimensional shapes. Name the shapes and suggest values for the bond
angles. Explain your reasoning.
(8)

(b) Perfume is a mixture of fragrant compounds dissolved in a volatile solvent.

When applied to the skin the solvent evaporates, causing the skin to cool for a short time.
After a while, the fragrance may be detected some distance away. Explain these
observations.
(4)
(Total 12 marks)

(a) An ammonium ion, made by the reaction between an ammonia molecule and a hydrogen
29 ion, can be represented as shown in the diagram below.

(i) Name the type of bond represented in the diagram by N—H

.............................................................................................................

Page 34 of 71
(ii) Name the type of bond represented in the diagram by N→H

.............................................................................................................

(iii) In terms of electrons, explain why an arrow is used to represent this N→H bond.

.............................................................................................................

(iv) In terms of electron pairs, explain why the bond angles in the NH4+ ion are all 109° 28’

.............................................................................................................

.............................................................................................................
(7)

(b) Define the term electronegativity.

......................................................................................................................

......................................................................................................................
(2)

(c) A bond between nitrogen and hydrogen can be represented as —

(i) In this representation, what is the meaning of the symbol δ+ ?

.............................................................................................................

(ii) From this bond representation, what can be deduced about the electronegativity of
hydrogen relative to that of nitrogen?

.............................................................................................................

.............................................................................................................
(2)
(Total 11 marks)

Page 35 of 71
(a) The shape of the molecule BCl3 and that of the unstable molecule CCl2 are shown below.
30

(i) Why is each bond angle exactly 120° in BCl3?

.............................................................................................................

(ii) Predict the bond angle in CCl2 and explain why this angle is different from that in BCl3

Predicted bond angle .........................................................................

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

.............................................................................................................
(5)

(b) Give the name which describes the shape of molecules having bond angles of 109° 28'.
Give an example of one such molecule.

Name of shape ............................................................................................

Example .......................................................................................................
(2)

(c) The shape of the XeF4 molecule is shown below.

(i) State the bond angle in XeF4

.............................................................................................................

(ii) Suggest why the lone pairs of electrons are opposite each other in this molecule.

.............................................................................................................

(iii) Name the shape of this molecule, given that the shape describes the positions of the
Xe and F atoms only.

.............................................................................................................
(4)

Page 36 of 71
(d) Draw a sketch of the NF3 molecule. Indicate in your sketch any lone pairs of electrons on
nitrogen.

(2)
(Total 13 marks)

Which one of the following ions has three lone pairs of electrons around the central atom?
31
A BF

B NH

C ClF

D PF
(Total 1 mark)

Which one of the following is the most likely value for the bond angle α shown in the diagram of
32
SF4 below?

A 118°

B 101°

C 90°

D 88°
(Total 1 mark)

Page 37 of 71
Which one of the following molecules or ions is pyramidal in shape?
33
A BF3

B CH

C CH

D SF
(Total 1 mark)

Which one of the following has a shape which is not influenced by a lone pair of electrons?
34
A CH3OH

B H 2F +

C BF3

D NF3
(Total 1 mark)

Page 38 of 71
Mark schemes
(a) Correct diagram of NH3 including LP on N
1 1
Correct diagram of AlCl3
1
Bond angles in range 106-108° and bond angle of 120°
1

Ignore shape names

(b) Dative (covalent) /co-ordinate bond

Wrong bond CE=0 but mark on if covalent quoted
1

Shared pair of / both electrons come from the N(H3)

(c) Aluminium is now surrounded by 4 electron pairs/bonds or is tetrahedral

Independent
1

Therefore Cl-Al-Cl bond angle decreases / changes

(from 120° in AlCl3 ) to allow range 107-111° in H3NAlCl3
1
[7]

(a) C(s) + 2F2(g) CF4(g)

2
State symbols essential
1

(b) Around carbon there are 4 bonding pairs of electrons (and no lone pairs)
1

Therefore, these repel equally and spread as far apart as possible

(c) ΔH = Σ ΔfH products – Σ ΔfH reactants or a correct cycle

Hence = (2 × –680) + (6 × –269) – (x) = –2889

x = 2889 – 1360 – 1614 = –85 (kJ mol–1)

1
Score 1 mark only for +85 (kJ mol–1)

Page 39 of 71
(d) Bonds broken = 4(C–H) + 4(F–F) = 4 × 412 + 4 × F–F

Bonds formed = 4(C–F) + 4(H–F) = 4 × 484 + 4 × 562

Both required
1

–1904 = [4 × 412 + 4(F–F)] – [4 × 484 + 4 × 562]

4(F–F) = –1904 – 4 × 412 + [4 × 484 + 4 × 562] = 632

F–F = 632 / 4 = 158 (kJ mol–1)

The student is correct because the F–F bond energy is much less than the C–H or
other covalent bonds, therefore the F–F bond is weak / easily broken
Relevant comment comparing to other bonds
(Low activation energy needed to break the F–F bond)
1
[10]

B
3 [1]

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

All stages are covered and the explanation of each stage is generally correct and
virtually complete.

Answer is communicated coherently and shows a logical progression from stage 1 to

stage 2 then stage 3.
Level 3
5 – 6 marks

All stages are covered but the explanation of each stage may be incomplete or may
contain inaccuracies OR two stages are covered and the explanations are generally
correct and virtually complete.

Answer is mainly coherent and shows progression from stage 1 to stage 3.

Level 2
3 – 4 marks

Two stages are covered but the explanation of each stage may be incomplete or may
contain inaccuracies, OR only one stage is covered but the explanation is generally
correct and virtually complete

Answer includes isolated statements but these are not presented in a logical order or
show confused reasoning.
Level 1
1 – 2 marks

Insufficient correct chemistry to gain a mark.

Level 0
0 marks

Page 40 of 71
Indicative chemistry content

Stage 1: Electrons round P

• P has 5 electrons in the outside shell
• With 3 electrons from 3 fluorine, there are a total of 8 electrons in outside shell
• so 3 bond pairs, 1 non-bond pair

Stage 2: Electron pair repulsion theory

• Electron pairs repel as far as possible
• Lone pair repels more than bonding pairs

Stage 3: Conclusions
• Therefore, tetrahedral / trigonal pyramidal shape
• With angle of 109(.5)° decreased to 107°
6

(b) 1s22s22p63s23p63d7
Allow correct numbers that are not superscripted
1

(c) Too many electrons in d sub-shell / orbitals

(d) Tetrahedral (shape)

109.5°
Allow 109°
1
[10]

(a) Silicon / Si
5
If not silicon then CE = 0 / 3
1

covalent (bonds)
M3 dependent on correct M2
1

Strong or many of the (covalent) bonds need to be broken / needs a lot of energy to
break the (covalent) bonds
Ignore hard to break
1

Page 41 of 71
(b) Argon / Ar
If not argon then CE = 0 / 3. But if Kr chosen, lose M1 and allow
M2+M3
1

Large(st) number of protons / large(st) nuclear charge

Ignore smallest atomic radius
1

Same amount of shielding / same number of shells / same number of energy levels
Allow similar shielding
1

(d) (i)

Or any structure with 3 bonds and 2 lone pairs

Ignore any angles shown
1

Or a structure with 2 bonds and 1 lone pair

(ii) Bent / v shape

Ignore non-linear, angular and triangular
Apply list principle
1

(iii) Cl2 + F2 ClF3

No multiples
Ignore state symbols
1
[11]

(a) 94−105.5°
6 1

Page 42 of 71
(b) (i) Hydrogen bond(ing) / H bonding / H bonds
Not just hydrogen
1

(ii)

1 mark for all lone pairs

1 mark for partial charges on the O and the H that are involved in H
bonding
1 mark for the H-bond, from Hδ+ on one molecule to lone pair on O
of other molecule
3

(c) Electronegativity of S lower than O or electronegativity difference between H and S is

lower
Mark independently
1

No hydrogen bonding between H2S2 molecules

Or only van der Waals / only dipole-dipole forces between H2S2 molecules
If breaking covalent bonds CE = 0
1
[7]

Page 43 of 71
(a)
7

Mark is for correct number of bonds and lone pair in each case.
Ignore charges if shown.
2

Pyramidal / trigonal pyramid

Allow tetrahedral.
1

107°
Allow 107 to 107.5°.
1

(b) M1 Ionic
CE = 0 / 3 if not ionic.
1

M2 Oppositely charged ions / Tl+ and Br− ions

If molecules / intermolecular forces / metallic bonding, CE=0.
1

M3 Strong attraction between ions

M3 dependent on M2.
Allow ‘needs a lot of energy to break / overcome’ instead of ‘strong’.
1

(a) Al + 1.5Cl 2 → AlCl3

8
Accept multiples.
Also 2Al + 3Cl2 → Al2Cl6
Ignore state symbols.
1

(b) Coordinate / dative (covalent)

If wrong CE=0/2 if covalent mark on.
1

Page 44 of 71
Electron pair on Cl − donated to Al(Cl 3)
QoL
Lone pair from Cl − not just Cl
Penalise wrong species.
1

(c) Al2Cl6 or AlBr3

Allow Br3Al or Cl6Al2
Upper and lower case letters must be as shown.
Not 2AlCl3
1

(d) SiCl4 / silicon tetrachloride

Accept silicon(4) chloride or silicon(IV) chloride.
Upper and lower case letters must be as shown.
Not silicon chloride.
1

(e)

Accept shape containing 5 bonds and no lone pairs from Tl to each

of 5 Br atoms.
Ignore charge.
1

Trigonal bipyramid(al)
1

(f) (i) Cl — Tl — Cl

Accept this linear structure only with no lone pair on Tl

(ii) (Two) bonds (pairs of electrons) repel equally / (electrons in) the bonds repel to
be as far apart as possible
Dependent on linear structure in (f)(i).
Do not allow electrons / electron pairs repel alone.
1

(g) Second
1
[10]

Page 45 of 71
(a)
9

Mark is for 3 As-Cl bonds and 1 lone pair

(Trigonal) pyramid(al) / tetrahedral

Allow triangular pyramid
1

Mark is for 2 Cl-Cl bonds and 2 lone pairs

Do not penalise if + not shown
1

Bent / V-shaped / triangular

Not trigonal
1

(b) There are 4 bonds or 4 pairs of electrons (around As)

Can show in a diagram. If lone pair included in shape, CE = 0 / 2
1

(Electron pairs / bonds) repel equally

QoL
1
[6]

(a)
10

Need to see 3 P–H bonds and one lone pair (ignore shape).
1

(b) Coordinate / dative

If not coordinate / dative then chemical error CE=0 unless blank or
covalent then M1 = 0 and mark on.
1

Page 46 of 71
Pair of electrons on P(H3) donated (to H+)
Do not allow a generic description of a coordinate bond.
1

(c) 109.5° / 109½ / 109° 28’

Allow answers in range between 109° to 109.5°
1

(d) Difference in electronegativity between P and H is too small

Allow P not very electronegative / P not as electronegative as N, O
and F / P not electronegative enough / P not one of the 3 most
electronegative elements.
Do not allow phosphine is not very electronegative.
1
[5]

(a) P = 100 000 (Pa) and V = 5.00 x 10–3 (m3)

11
M1 is for correctly converting P and V in any expression or list Allow
100 (kPa) and 5 (dm3) for M1.
1

M2 is correct rearrangement of PV = nRT

= 0.202 moles (of gas produced)

This would score M1 and M2.

Therefore = 0.0404 moles B2O3

M3 is for their answer divided by 5

Mass of B2O3 = 0.0404 x 69.6

M4 is for their answer to M3 x 69.6
1

= 2.81 (g)
M5 is for their answer to 3 sig figures.
2.81 (g) gets 5 marks.
1

(b) B + 1.5 Cl2 → BCl3

Accept multiples.
1

Page 47 of 71
3 bonds
1

Pairs repel equally/ by the same amount

Do not allow any lone pairs if a diagram is shown.
1

(c) (i) 43.2/117.3 (= 0.368 moles BCl3)

0.368 x 3 (= 1.105 moles HCl)

Allow their BCl3 moles x 3
1

Conc HCl =

Allow moles of HCl × 1000 / 500

= 2.20 to 2.22 mol dm–3

Allow 2.2
Allow 2 significant figures or more
1

(ii) H3BO3 + 3NaOH → Na3BO3 + 3H2O

Allow alternative balanced equations to form acid salts.
Allow H3BO3 + NaOH → NaBO2 + 2H2O
1

(d)

Mark is for both Mr values correctly as numerator and denominator.

8.98(%)
Allow 9(%).
1

Sell the HCl

(e) Alternative method

Cl = 86.8%
Cl = 142 g
1

Page 48 of 71
B Cl

B Cl

1.22 2.45 or ratio 1:2 or BCl2

2:4 ratio
1

BCl2 has Mr of 81.8 so

81.8 x 2 = 163.6
Formula = B2Cl4
B2Cl4
Allow 4 marks for correct answer with working shown.
Do not allow (BCl2)2
1
[20]

(a) Covalent
12
If not covalent CE = 0/2
If dative covalent CE = 0/2
If blank mark on
Ignore polar
If number of pairs of electrons specified, must be 3
1

Shared pair(s) of electrons / one electron from Br and one electron from F
Not 2 electrons from 1 atom
Not shared pair between ions/molecules
1

(b) (i)

BrF3 should have 3 bp and 2 lp and correct atoms for the mark
Penalise Fl
1

Page 49 of 71
BrF3 if trigonal planar shown = 120°
Allow 84 – 90° or 120° and ignore 180°

or if T shape shown 84 – 90°

Irrespective of shape drawn
1

(ii)

BrF4– should have 4 bp and 2 lp and all atoms for the mark
(ignore sign)
Allow Fl
1

BrF4– 90°
Only
Ignore 180°
1

(c) Ionic or (forces of) attraction between ions / bonds between ions
If molecules, IMF, metallic, CE =0
If covalent bonds mentioned, 0/3, unless specified within the BrF4–
ion and not broken
Ignore atoms
1

Strong (electrostatic) attraction / strong bonds / lots of energy needed to break

bonds
1

Between K+ and BrF4– ions/oppositely charged ions / + and – ions

If ions mentioned they must be correct
Strong bonds between + and – ions =3/3
1

(d) (i) Hydrogen bonds/hydrogen bonding/H bonds/H bonding

Not just hydrogen
1

Page 50 of 71
(ii)

One mark for 4 partial charges

One mark for 6 lone pairs
One mark for H bond from the lone pair to the Hδ+
Allow Fl
If more than 2 molecules are shown they must all be correct.
Treat any errors as contradictions within each marking point.
CE = 0/3 if incorrect molecules shown.
3

(e) vdw / van der Waals forces between molecules

QoL
Not vdw between HF molecules, CE = 0/2
vdw between atoms, CE = 0/2
If covalent, ionic, metallic, CE=0/2
1

IMF are weak / need little energy to break IMF / easy to overcome IMF
1
[15]

(a) Iodine has more electrons / iodine is bigger (atom or

13 molecule) / iodine has bigger Mr / bigger surface area
1

Stronger / more van der Waals forces / vdw / London /

temporarily induced dipole / dispersion forces between
molecules
1
Stronger VdW intermolecular forces = M2
If stated VdW between atoms lose M2

(b) (i)

Mark is for 3 bp and 1 lp attached to N (irrespective of shape)

Page 51 of 71
Mark is for 3 bp and 0 lp attached to B (irrespective of shape)
1

NHF2 shape - pyramidal / trigonal pyramid

Accept tetrahedral / triangular pyramid
1

BF3 shape - trigonal planar

Not triangular or triangular planar
1

(ii) 107°
Allow 106-108°
1

(c) Hydrogen bonds

Allow H-Bonds
Not just Hydrogen
Apply list principle eg Hydrogen bonding and dipole-dipole = 0
1

(d) Coordinate / dative covalent / dative

If covalent mark on
If ionic / metallic CE = 0
1

Lone pair / both electrons/ 2 electrons on N(HF2) donated (to BF3)

Direction of donation needed here
1
[10]

Page 52 of 71
(a) Water or H2O or molecules (in ice) are held further apart
14 (than in liquid water)/(more) space/gaps/holes in structure/Water
or H2O or molecules (in ice) are more spread out
Allow water (liquid) is more compact/less space/gaps/holes
CE if holes filled with air, O2 etc
CE if macromolecule
CE if atoms further apart (since ambiguous)
Ignore spaces filled with H2O
Ignore reference to H bonds
Allow better tessellation in liquid water
1

(b) (i) Hydrogen bonding

Allow H bonds
Do not allow ‘hydrogen’ only but mark on
1

(ii) Van der Waals’/VdW

Allow London forces, dispersion forces, temporary induced dipole
forces
1

(iii) Hydrogen bonding is stronger (than van der Waals forces)/IMF in

ice stronger (than IMF in methane)/H bonds take more energy
to break
Not H Bonds are strong (needs comparison)
If (b)(i) OR (ii) is incorrect, cannot award (b)(iii)
If (b)(i) and/or (ii) is blank, can score (b)(iii)
1

(c) (i) Structure showing 3 bonds to H and 1 lone pair

(trigonal) pyramid(al)/(distorted) tetrahedral

do not insist on the + sign
Allow triangular pyramid
Not square pyramid
Ignore bond angles in structure
M2 independent of M1
1

(ii) 107°
Allow range 106 – 108°
Ignore °(C)
1

Page 53 of 71
(iii) NH3/ammonia
Contradictions (eg NH4 ammonia) CE = 0
1

(d) 3
Allow three/III/3 lone pairs/3lp/3 lone pairs of electrons
1
[9]

(a) (i) shared pair of electrons

15
Can have one electron from each atom contributes to the bond
Not both electrons from one atom
1

(ii) Cl2 + F2 → ClF3

1
Only
Ignore state symbols even if wrong

(b)

Page 54 of 71
OR
Allow any structure with 4 bp
In CClF2, watch for Cl in centre- it must be C
Ignore wrong bond angles
Representations of lone pairs allowed are the two examples shown
with or without the electrons in the lobe.
Also they can show the lone pair for either structure by two
crosses/dots or a line with two crosses/dots on it e.g.

or
Or a structure with 3 bp and 2 lp
1

(c) Dipole – dipole

Allow van der Waals/vdw/London/dispersion/temporary dipole –
induced dipole
Not dipole alone
1

(d) (i) Coordinate/dative (covalent)

If wrong CE = 0/3 but if ‘covalent’ or left top line blank, mark on.
1

(Lone) pair of electrons/both electrons (on F–)

CE if lone pair is from B
1

Donated from F–/fluoride or donated to the BF3

Must have the – sign on the F ie F–
Ignore Fl–
M3 dependent on M2
1

(ii) 109° to 109.5°

Page 55 of 71
(e)
For 1 mark allow 238 as numerator and 438 as denominator or
correct strings
1

= 54.3%
2 marks if correct answer to 3 sig figs.
54% or greater than 3 sig figs = 1 mark
1
[11]

Page 56 of 71
16

Mark M1 – M5 independently
M1 for 5 bond pairs around As
Do not penalise A for As or Fl for F
1

trigonal/triangular bipyramid(al)
Allow trigonal dipyramid
1

M3 for 2 bond pairs to F and 2 lone pairs

Lone pairs can be shown as lobes with or without electrons or as xx
or
x
x
1

Bent/V shape/non-linear/triangular/angular
Bent-linear = contradiction
Do not allow trigonal
1

104° – 106°
1

(For candidates who thought this was CIF2+ which contained iodine allow

Trigonal/triangular planar
Not just triangular

120°
[5]

Page 57 of 71
(a) 2s2 2p6;
17
If ignored the 1s2 given and written 1s22s22p6 mark as correct
Allow capitals and subscripts
1

(b) (i) Na+(g) → Na2+ (g) + e(–);

One mark for equation and one mark for state symbols

Na+(g) + e(–) → Na2+ (g) + 2e(–);

M2 dependent on M1
Allow Na+(g) – e(–) → Na(g)
Allow X+(g) → X2+ (g) + e = 1 mark
2

(ii) Na(2+) requires loss of e– from a 2(p) orbital or 2nd energy level or
2nd shell and Mg(2+) requires loss of e– from a 3(s) orbital or 3rd
energy level or 3rd shell / Na(2+) loses e from a lower (energy)
orbital/ or vice versa;
Not from 3p
1

Less shielding (in Na);

Or vice versa for Mg
1

e(–) closer to nucleus/ more attraction (of electron to nucleus) (in Na);
M3 needs to be comparative
1

(iii) Aluminium /Al;

Increasing nuclear charge/ increasing number of protons;

Electrons in same shell or level/ same shielding/ similar shielding;

Page 58 of 71
(d) Answer refers to Na;
Allow converse answers relating to Mg.

Na fewer protons/smaller nuclear charge/ fewer delocalised electrons;

Allow Mg is 2+ and Na is +.
If vdw CE = 0.
1

Na is a bigger ion/ atom;

Smaller attraction between nucleus and delocalised electrons;

If mentioned that charge density of Mg2+ is greater then allow first 2
marks.
(ie charge / size / attraction).
M3 allow weaker metallic bonding.
1

(e) (Bent) shape showing 2 lone pairs + 2N−H bond pairs;

Atoms must be labelled.
Lone pairs can be with or without lobes.
1

Bent / v shape/ triangular;

Not tetrahedral.
Allow non-linear.
Bent-linear = contradiction.
1

(f) Ne has full sub-levels/ can’t get any more electrons in the sub-levels/
Ne has full shells;
Not 2s2 2p6 alone.
Not stable electron configuration.
1
[16]

(a) Ability/power of an atom/element/nucleus to withdraw electron

18 density or electron cloud or a pair of electrons (towards itself);
Not withdraw an electron
If ref to ionic, metallic , imf etc then CE = 0
1

From a covalent bond or from a shared pair of electrons;

Not distort
Not remove electrons
1

Page 59 of 71
(b) Van der Waals/ vdw/London/ temporary (induced) dipole/
dispersion forces;
1

Hydrogen bonds/H bonds;

Not just hydrogen
1

(c) (Large) electronegativity difference between N + H/ difference

of 0.9/ N very electronegative;
Insufficient to say N= 3.1 and H = 2.1
1

Forms N δ– / H δ+ or dipole explained in words;

Not N becomes (fully) negative or vice versa
1

Lone pair on N attracts/forms weak bonds with H (δ+);

QWC
Can score M2 and 3 from a diagram
1

(d) Co-ordinate/dative;
If not correct then CE = 0. If covalent/blank mark on.
1

Both electrons/ lone pair (on P/PH3)

Not lone pair on hydrogen
1

Shares/donated from P(H3)/ to H(δ+);

(e) 3 bonds and 1 lp attached to As;

Must label H and As atoms
Accept distorted tetrahedral not bent tetrahedral
1

Pyramidal/tetrahedral/ trigonal pyramidal;

Not bipyramidal/triangular
1

(f) (Only) weak Van der Waals forces between molecules /AsH3
has weaker IMF /ammonia has hydrogen bonding/ more
energy needed to break IMF’s in ammonia/ Van der Waals
weaker than H bonds;
Accept has no H bonds.
Ignore dp-dp in AsH3 provided ammonia has stronger IMF.
If between atoms mentioned CE=0
Break bonds CE = 0
1

Page 60 of 71
(g) 4AsCl3 + 3NaBH4 → 4AsH3 + 3NaCl + 3BCl3;
Accept multiples
1
[14]

(a) NaCl is ionic

19 1
cubic lattice
1
ions placed correctly
1
electrostatic attraction between ions
1
Covalent bonds between atoms in water
1
Hydrogen bonding between water molecules
1
Tetrahedral representation showing two covalent
and two hydrogen bonds
1
2 hydrogen bonds per molecule
1
Attraction between ions in sodium chloride is very strong
1
Covalent bonds in ice are very strong
1
Hydrogen bonds between water molecules in ice are much weaker
1
Consequently, less energy is required to break the hydrogen
bonds in ice to form separate water molecules than to
break the ionic bonds in sodium chloride and make separate ions
1

Page 61 of 71
(b)
The marking scheme for this part of the question includes an overall
assessment for the Quality of Written Communication (QWC). There
are no discrete marks for the assessment of QWC but the
Mark candidates’ QWC in this answer will be one of the criteria used to
Range assign a level and award the marks for this part of the question
Descriptor
an answer will be expected to meet most of the criteria in the level
descriptor

3 – claims supported by an appropriate range of evidence

– good use of information or ideas about chemistry, going beyond
those given in the question
– argument well structured with minimal repetition or irrelevant
points
– accurate and clear expression of ideas with only minor errors of
grammar, punctuation and spelling

2 – claims partially supported by evidence

– good use of information or ideas about chemistry given in the
question but limited beyond this
– the argument shows some attempt at structure
– the ideas are expressed with reasonable clarity but with a few
errors of grammar, punctuation and spelling

0-1 – valid points but not clearly linked to an argument structure

– limited use of information or ideas about chemistry
– unstructured
– errors in spelling, punctuation and grammar or lack of fluency

4 bonding electron pairs

1
and one lone pair
1
repel as far apart as possible QWC
1
lone pair - bond pair repulsion > bp—bp QWC
1
pushes S-F bonds closer together
1
shape is trigonal bipyramidal with lone pair either
axial or equatorial QWC
1
angles <90
1
and < 120
1
[20]

Page 62 of 71
(i)
20

(1) (1)
[Do not allow shapes which show a lone pair]
2

BF3 Trigonal planar/planar triangular

[Not plane triangle]
1

BF Tetrahedral
[Not distorted tetrahedral]
1

Equal repulsion between (4) bonding pairs/bonds/bonding electrons

109(½)°
1

(ii) Lone pair donated / both electrons supplied by one atom

from F– (to B)
[ignore missing charge or fluorine or ‘atom’]
1

dative/dative covalent/coordinate bonding

1
[9]

A
21 [1]

Page 63 of 71
(penalty for sig fig error =1 mark per question)
22
(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

17
(b) 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

Page 64 of 71
(d) Mr (Mg(NO3)2 = 58(.3) (if At N 0 used, lose M1 and M2)
1

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

(a) dative / coordinate (covalent) bond;

23 1

Lone/non-bonding pair / both electrons;

(donated) from P to H+;

(b)

pyramidal OR trigonal pyramid 109( )°;

(accept tetrahedral)
4
[7]

Page 65 of 71
B
24 [1]

(a) (i) 2Na + 2NH3 → 2NaNH2 + H2

25
(or multiples)
1

(ii) (Missing ‘H’ penalise once only) [NOT dot-and-cross diagrams]

[NOT 90° / 180° angles] (need 2 lp & ‘bent’ shape)

(iii) 107°
1

(iv) More lone pairs on NH2–, than on NH3

Lone pairs repel more than bonding pairs

Must be comparison
(Mark separately)
[NOT repulsion between atoms or between bonds]
1

(b) (i) Simplest ratio of atoms of each element in a

compound / substance / species / entity / molecule
1

(ii) Mg N O

(0.675) 0.667 1.37 4.06

1 2 6 MgN2O6
(Mark M1 first. If any wrong Ar used = CE = 0)
(Accept Mg(NO3)2 for M3 if above working shown)
1
[9]

Page 66 of 71
(a) 4LiH + AlCl3 → LiAlH4 + 3LiCl
26 1

(b) H – = 1s2 or 1s2

(c) Tetrahedral or diagram

(Not distorted tetrahedral)
1

(Equal) repulsion
1

between four bonding pairs / bonds

(Not repulsion between H atoms loses M2 and M3)
(Not ‘separate as far as possible’)
(‘4’ may be inferred from a correct diagram)
1

(d) Dative (covalent) or coordinate

Lone pair or non-bonding pair of electron or both e–

QoL Donated from H– to Al or shared between H and Al

(tied to M2)
–
(Not ‘from H atom’) (Not ‘to Al ion’) (Not ‘e s transferred’)
1
[8]

(a) (i) Electronegativity (difference) or suitable description (1)

27
Accept F and Cl are highly electronegative
Not both atoms are highly electronegative

(ii) HF = hydrogen bonding (1)

HCl = (permanent) dipole-dipole bonding or even van de Waals’ (1)
Hydrogen bonding stronger / is the strongest IMF (1)
Accept a statement that HF must have the stronger IMF, even if no
IMFs identified
The explanation must be based on intermolecular
forces/attractions
Note: if the explanation is clearly intramolecular = CE
4

Page 67 of 71
(b) Electron pair or lone pair donated (1)
Do not accept ‘donation of electrons’

From chloride ion to Al or AlCl3 (1)

M1 can be earned by a general explanation of coordinate bonding,
even if the electron pair is said to come from Al. The second mark,
M2, is for this specific bond
Ignore missing charge
2

PCl5 shown as trigonal bipyramid PCl4+ shown as tetrahedral

[Look for: ONE solid linear Cl-P-Cl bond] NO solid linear Cl-P-Cl bonds]

Bond Angle(s) 90° and 120° (1) Bond angle(s) 109 or 109.5° (1)
[10]

(a) SF6 shown as octahedral / square based bipyramid (1)

28 Bond angle: 90° or 180° and 90° (1)
Shape = octahedral (1)
If lone pair shown then C.E. = 0 / 4

Wrong symbols ‑ no diagram mark

Equal repulsion between 6 bonding or shared electron pairs QoL (1)

Page 68 of 71
AlCl4– shape shown as tetrahedral (1)
Bond angle = 109° to 109.5° (1)
Shape = tetrahedral (1)
If lone pair shown then C.E = 0/4

(Equal repulsion between) 4 bonding pairs or shared electron pairs (1)

QoL may be awarded here also
Mark all points independently
8

(b) Solvent has low bp or weak intermolecular forces or evaporates quickly (1)

(Solvent) needs energy to evaporate (to overcome intermolecular forces)

or valid reference to latent heat of vaporisation (or evaporation is
endothermic) (1)
OR higher energy or faster molecules more likely to escape
so mean energy (and hence temperature) falls

Energy taken from the skin (and so it cools) (1)

Fragrance or perfume (molecules) slowly spreads (through the room) (1)

By random movement or diffusion (of the perfume / fragrance) (1)

4
[12]

(a) (i) Covalent (1)

29
(ii) Co-ordinate (1) (or dative)

(iii) Both / two / pair electrons come from nitrogen (1)

(iv) 4 bonding / electron pairs (1)

repel equally (1)

OR are identical

as far apart as possible (1)

OR to position of minimum repulsion

tetrahedron (1)
7

Page 69 of 71
(b) Power (or ability) of an element / atom to attract electron pair/electrons/
an electron/electron density (1)

in a covalent bond (1)

Allow attract from, withdraw in, do not allow remove
from, withdraw from.
2

(c) (i) Electron deficient (1)

Or small, slight, partial positive charge

(ii) H < N (1)

2
[11]

(a) (i) 3 (bonding) pairs of electrons (1)

30
allow 3 bonds

repel equally (1) (or as much as possible)

Or get as far apart as possible

(ii) Predicted bond angle: 118° (allow 117 - 119°) (1)

Explanation: lone pair (1)
repels more than bonding pair (1)
Allow EXP if < 118°
but C.E. = 0 if 120°
5

(b) Name of shape: Tetrahedral (1)

Example: CH4 etc (1)
Allow correct ion
2

(c) (i) 90° (1)

(ii) lone pairs (or they) repel more than bonding pairs (or most) (1)
(so are) as far apart as possible (1)
Mark independently

(iii) square planar (1)

allow square
4

Page 70 of 71
(d)

Penalise sticks (i.e. N‑) once but N must be shown

2
[13]

C
31 [1]

A
32 [1]

C
33 [1]

C
34 [1]

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