CCEA A2 Chemistry Exam Practice - Mark Scheme - v4 - Unit A2 1 - Further Physical and Inorganic Chemistry - 4.1 Lattice Enthalpy

Sep 26, 2026

Mark scheme for CCEA A2 Chemistry Exam Practice, version v4, focused on Unit A2 1: Further Physical and Inorganic Chemistry. Provides answers and mark breakdown for Section 4.1 Lattice Enthalpy and begins Section 4.2 on Enthalpy, Entropy and Free Energy. Includes definitions of lattice enthalpy, enthalpy-related reasoning for formation and solution processes, numerical calculations using given thermodynamic data, and guidance on common errors. Also supplies balanced ionic half-equations and assessment notes for diagrams, charges, bonding, and exothermic/endothermic steps.

LanguageEnglish

CategoryExam

FormatPDF

Pages93

Reading Time3 h 54 min

AccessFree to download

4.1 Lattice Enthalpy

Definitions and key concepts

Worked answers and mark allocations

4.2 Enthalpy, Entropy and Free Energy

Entropy and predicting entropy changes

Alyn G McFarland Nora Henry CCEA A2 CHEMISTRY EXAM PRACTICE MARK SCHEME This mark scheme is for use in conjunction with the book Chemistry Exam Practice for CCEA A2, ISBN: 978 1 78073 254 1 Colourpoint Educational An imprint of Colourpoint Creative Ltd Colourpoint House Jubilee Business Park 21 Jubilee Road Newtownards County Down Northern Ireland BT23 4YH Tel: 028 9182 0505 E-mail: [sales@colourpoint.co.uk](sales@colourpoint.co.uk) [Web site: www.colourpointeducational.com](Web site: www.colourpointeducational.com) ©2021 Alyn G McFarland, Nora Henry and Colourpoint Creative Ltd. All rights reserved. This material is provided solely for use with the accompanying textbook. Unauthorised reproduction, in whole or part, without prior written permission from the publisher is prohibited. Publisher’s Note: These answers have been written to help students preparing for the A2 Chemistry specification from CCEA. While Colourpoint Educational and the author have taken every care in its production, we are not able to guarantee that it is completely error-free. Additionally, while the mark scheme has been written to closely match the CCEA specification, it is the responsibility of each candidate to satisfy themselves that they have fully met the requirements of the CCEA specification prior to sitting an exam set by that body. For this reason, and because specifications change with time, we strongly advise every candidate to avail of a qualified teacher and to check the contents ofthe most recent specification for themselves prior to the exam. Colourpoint Creative Ltd therefore cannot be held responsible for any errors oromissions in this mark scheme or any consequences thereof. v4 Unit A2 1: Further Physical and Inorganic Chemistry Answers 4.1 LATTICE ENTHALPY 4.1 Lattice Enthalpy 1 C [1] 2 B [1] Enthalpy of solution = lattice enthalpy + hydration enthalpy of calcium ion + 2 × hydration enthalpy of chloride ion = + 2237 + (–1650) + 2(–364) = –141 kJ mol–1. Most common error would be forgetting the 2 × for the enthalpy of hydration of the chloride ion. This would give answer C. 3 (a) the energy required to convert one mole of gaseous atoms into gaseous ions with a single positive charge. [2] (b) enthalpy change when one mole of a compound is formed from its elements under standard conditions. [2] (c) enthalpy change when one mole of gaseous atoms is formed from the element in its standard state. [2] (d) enthalpy change when one mole of an ionic compound is converted to gaseous ions. [2] 4 (a) (i) Cs(g) 􀃆 Cs+ (g) + e– [ 1] (ii) Cs(s) + ½Cl2 (g) 􀃆 CsCl(s) [ 1] (iii) Cl(g) + e– 􀃆 Cl–(g) [ 1] (iv) CsCl(s) 􀃆 Cs+ (g) + Cl–(g) [ 1] (b) (i) Cs+(g) + Cl(g) + e– |
Cs+(g) + ½Cl2(g) + e– | | | Cs+(g) + Cl–(g) | | | --- | --- | --- | --- | --- | | Cs(g) + ½Cl2(g) |
CsCl(s)
| | | | | Cs(s) + ½Cl2(g) | | | | | | | | | | | [1] for each correct level with state symbols [3] (ii) lattice enthalpy = –(–433) + (+78) + (+380) + (+122) + (–364) = + 649 kJ mol–1 [2] (c) Cs+ ion larger ionic radius than other Group I metal ions [1] weaker ionic bonding as ions not as close packed [1] [2] 5 (a) A, D, B, E, C, F all correct [2]; one error [1] [2] (b) lattice enthalpy = –(–642) + (+150) + (+736) + (+1450) + (+242) + 2(–364) = + 2492 kJ mol–1 [3] 1 4.1 LATTICE ENTHALPY (c) –165 = + (+2492) + (–1891) + (2x) 2x = –766 x = –383 kJ mol–1 [3] (d) H δ+ H δ+ δ+ H H δ+ δ+ δ+ H ~~ ~~ O O ~~ ~~ H δ+ O H δ+ H Oδ– δ– δ– δ– Mg2+ Cl – δO– δO– H δ+ δ+ H H Oδ– δ+H δ+ H δ+ H H δ+ Oδ– δ+ [1] for each diagram with partial charges and bonds to ions bonds form between water molecules and ions [1] bond formation is exothermic [1] [4] 6 (a) Ag+(g) + F(g) + e– |
Ag+(g) + ½F2(g) + e– | | | Ag+(g) + F–(g) | | | --- | --- | --- | --- | --- | | Ag(g) + ½F2(g) |
AgF(s) | | | | | Ag(s) + ½F2(g) | | | |

FAQs

What does the mark scheme cover for Unit A2 1 in this document?

It covers answers and marking guidance for topics including 4.1 Lattice Enthalpy and the start of 4.2 Enthalpy, Entropy and Free Energy, with calculation steps, equations, and diagram marking notes.

How is lattice enthalpy used in the provided calculations?

The answers combine lattice enthalpy with related hydration or solution enthalpies, using provided numerical data and ensuring correct stoichiometric factors (e.g., the required “2 ×” term for certain ions).

What are the marking focuses for diagrams and ionic processes in 4.1?

Marks are allocated for correct energy values, correct level-by-level state symbols and charges, and diagrams showing partial charges and bonds to ions or water, including whether steps are exothermic or endothermic.

Sep 26, 2026

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