Edexcel A-Level Chemistry Paper 1, June 2022: Question 4

12 marks · Hard difficulty · Extended Writing

Assess various aspects of bonding and structure including ionic radii, electrolysis of copper(II) chromate(VI), properties of giant lattices, and anomalous properties of water such as hydrogen bonding and ice density.

Practise this question

Question

Question text

4 This question is about structure and bonding.

(a) Ionic bonding is the strong electrostatic attraction between

(1)

A anions and cations

B atoms and delocalised electrons

C cations and delocalised electrons

D two nuclei and a shared pair of electrons

(b) An aqueous solution of copper(II) chromate(VI) was electrolysed using the

apparatus shown in the diagram.

6V DC

+ –

E F

copper(II) chromate(VI)

solution

Deduce the colours of the solutions in regions E and F after the electrolysis

has occurred.

(2)

Colour in region E …

Colour in region F …

Ion Ionic radius / nm

Na+ 0.102

Mg2+ 0.072

Cl– 0.180

Br– 0.195

Deduce the formula*P67093RA0932*of the compound, formed from the ions in the table, that has

the strongest ionic bonding.

(1)

(d) The names of four substances are given.

Substance Name

P copper

Q iodine

R silicon(IV) oxide

S sodium chloride

(i) Which of these substances exists at room temperature as a giant lattice of

oppositely charged ions?

(1)

A Substance P

B Substance Q

C Substance R

D Substance S

(ii) Which of these substances has a high melting temperature, and conducts

electricity when solid and when molten?

(1)

A Substance P

B Substance Q

C Substance R

D Substance*P67093RA01032*S

*(e) Water has two significant anomalous properties:

• it has a higher melting temperature than hydrogen sulfide, H2S, even

though it has fewer electrons in its molecules

• the density of ice at 0°C is less than that of water at 0°C.

Explain these properties.

You should include a labelled diagram to show the intermolecular forces between

two molecules of water.

(6)

… 11

*P67093RA01132*

… *P67093RA01232*

(Total for Question 4 = 12 marks)

Mark scheme

Show the mark scheme

Question Answer Mark

number

4(a) (1)

The only correct answer is A (anions and cations)

B is incorrect because ionic bonding involves positive ions and negative ions

C is incorrect because there are no delocalised electrons in ionic bonding

D is incorrect because this is a description of covalent bonding

Question

Answer Additional Guidance Mark

Number

4(b) (2)

• region E: yellow (1) Ignore additional descriptions of

colours e.g. pale, bright

• region F: blue (1)

Do not award any other colours e.g.

blue-green

Question

Answer Additional Guidance Mark

Number

4(c) (1)

• MgCl2 Ignore names

Do not award MgCl

number

4(d)(i) (1)

The only correct answer is D (Substance S)

A is incorrect because copper exists as a giant metallic lattice

B is incorrect because iodine exists as a simple molecular lattice

C is incorrect because silicon(IV) oxide exists as a giant covalent lattice

number

4(d)(ii) (1)

The only correct answer is A (Substance P)

B is incorrect because iodine has a low melting temperature and does not conduct electricity

C is incorrect because silicon(IV) oxide does not conduct electricity

D is incorrect because sodium chloride does not conduct electricity when solid

Question

Acceptable Answers Additional Guidance Mark

Number

4(e)* This question assesses a student’s ability to show a Guidance on how the mark scheme should (6)

coherent and logically structured answer with linkages and be applied:

fully-sustained reasoning. The mark for indicative content should be

added to the mark for lines of reasoning. For

Marks are awarded for indicative content and for how the example, an answer with five indicative

answer is structured and shows lines of reasoning. marking points that is partially structured

with some linkages and lines of reasoning

The following table shows how the marks should be scores 4 marks (3 marks for indicative

awarded for indicative content. content and 1 mark for partial structure and

some linkages and lines of reasoning).

Number of Number of If there are no linkages between points, the

indicative marks awarded same five indicative marking points would

marking for indicative yield an overall score of 3 marks (3 marks for

points seen in marking points indicative content and no marks for

answer linkages).

5–4 3

3–2 2

The following table shows how the marks should be

awarded for structure and lines of reasoning.

Number of marks

awarded for

structure of

answer and

sustained line of

reasoning

Answer shows a coherent and 2

logical structure with linkages

and fully sustained lines of

reasoning demonstrated In general it would be expected that 5 or 6

throughout. indicative points would get 2 reasoning

Answer is partially structured 1 marks, and 3 or 4 indicative points would get

with some linkages and lines of 1 mark for reasoning, and 0, 1 or 2 indicative

reasoning. points would score zero marks for

Answer has no linkages 0 reasoning.

between points and is

unstructured.

Comment:

Look for the indicative marking points first, then consider General points to note

the mark for structure of answer and sustained line of If there is any incorrect chemistry, deduct

reasoning mark(s) from the reasoning. If no reasoning

mark(s) awarded do not deduct mark(s).

Example of incorrect chemistry

Reference to ionic bonding/ions

Ignore reference to intermolecular forces

other than London forces in H2S

Indicative content

• IP1 – lone pair and dipole

lone pair on oxygen in hydrogen bond and dipole shown

with δ+ on any one H and δ− on any one O

Example of diagram

• IP2 – shape

Comment: allow bond angles drawn

hydrogen bond labelled / or shown as a dotted line 0 0 0

between 170 and 190 if labelled 180

and hydrogen bond(s) shown as approximately linear or

If multiple hydrogen bonds are drawn the

O-H-O bond angle labelled 180°

majority must be within this tolerance

• IP3 – London forces

Allow / attractions between temporary

hydrogen sulfide has stronger London forces/ dispersion

dipoles and induced dipoles / instantaneous

forces / van der Waals’ forces (because it has more

dipole - induced dipole for London forces

electrons)

Do not award breaking of covalent bonds

• IP4 – comparison

Allow hydrogen bonds take a lot of energy to

hydrogen bonding is stronger than London forces / is

break as long as hydrogen bonds are only

the strongest intermolecular force / requires more

mentioned as being present in the water

energy to break/ requires more energy to overcome

• IP5 – ice at 00C

Allow this shown in a diagram

(water molecules are arranged) in a lattice / hexagon Allow rings (of 6 for hexagonal)

or hydrogen bonds are longer than covalent bonds Allow there are spaces / air / gaps in the

structure

• IP6 – water at 00C

Allow (water) molecules fill the spaces/gaps

(water) molecules get closer / have less distance

Allow reverse argument

between them / more molecules in the same volume

(Total for Question 4 = 12 marks)

Question

Answer Additional Guidance Mark

Number

How to answer it

Structure and Bonding Exam Study Guide

What this question tests

This comprehensive question assesses your foundational understanding of chemical bonding types, ionic properties, electrolysis of colored ions, crystal lattices, metallic conductivity, and the anomalous properties of water governed by hydrogen bonding and London forces.

Question Part (a)

Definition of Ionic Bonding

✅ Correct Answer

A – anions and cations

💡 Key Knowledge

Ionic bonding is defined strictly as the strong electrostatic attraction between oppositely charged ions (cations and anions).

❌ Common Errors

Students often incorrectly choose option C, forgetting that delocalized electrons are exclusive to metallic lattices, not ionic compounds.

Mark: 1 mark

Question Part (b)

Electrolysis of Aqueous Copper(II) Chromate(VI)

✅ Correct Answers

Region E (near positive electrode): yellow
Region F (near negative electrode): blue

🧠 Exam Technique

Consider ion migration: Negatively charged chromate ions ( CrO₄²⁻ ) are yellow and migrate towards the positive electrode (E). Positively charged copper(II) ions ( Cu²⁺ ) are blue and migrate towards the negative electrode (F).

❌ Common Errors

Do not write mixed descriptions like "blue-green". The mark scheme strictly requires distinct, single-color identifiers for each region.

Marks: 2 marks (1 per region)

Question Part (c)

Ionic Radii and Bond Strength

✅ Correct Answer

MgCl₂ (Accept MgCl2 ; ignore names, do not award Mgcl2 formatting errors).

💡 Key Knowledge

Stronger ionic bonding occurs when ions are smaller in radius and carry higher ionic charges, increasing charge density and electrostatic attraction.

❌ Common Errors

Writing lowercase element symbols (e.g., mgcl2 ) or failing to use proper subscript numbers will lose you the mark.

Mark: 1 mark

Question Part (d) - (i) & (ii)

Lattice Structures and Electrical Conductivity

✅ Correct Answers

(i) D (Substance S - sodium chloride)
(ii) A (Substance P - copper)

💡 Key Knowledge

Giant ionic lattices consist of oppositely charged ions. Metals like copper possess delocalized electrons, allowing them to conduct electricity both in solid and molten states.

❌ Common Errors

Confusing simple molecular substances (like iodine) with giant covalent structures (like silicon(IV) oxide) is a frequent pitfall.

Marks: 2 marks total (1 per sub-part)

Question Part (e)

Anomalous Properties of Water & Hydrogen Bonding

✅ Correct Answers & Indicative Content

IP1: Lone pair on oxygen in hydrogen bond, showing partial charges ( δ+ on H, δ- on O).
IP2: Hydrogen bond shown as a dotted line, approximately linear with an O-H...O bond angle of 180°.
IP3: Water has stronger London forces than H₂S because it has more electrons per molecule.
IP4: Hydrogen bonding is stronger than London forces, requiring more energy to break.
IP5: Ice at 0°C arranges molecules in an open lattice / hexagonal ring structure with longer hydrogen bonds.
IP6: Liquid water molecules get closer together as the open structure collapses, increasing density.

🧠 Exam Technique & Diagram Requirements

Your diagram must clearly illustrate:

At least two water molecules with correct polarities ( δ+ / δ- ).
A dotted line representing the hydrogen bond between a lone pair on O and a hydrogen atom.
A linear 180° bond angle centered around the hydrogen bond interaction.

❌ Common Errors

Do not state that covalent bonds break when ice melts or water boils. Ensure you compare permanent/hydrogen bonding properly against London (dispersion) forces without citing incorrect intermolecular forces for H₂S .

Marks: 6 marks total (4 for indicative content points + 2 for structure and lines of reasoning)

Topics

Physical Chemistry · Inorganic Chemistry · Topic 2: Bonding and Structure · Topic 15: Transition Metals

Question and mark scheme from the Edexcel A-Level Chemistry examination, Paper 1, June 2022. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.