CAIE A Level Chemistry 9701 · Chemical energetics
Reaction 1: ΔH = +100 kJ mol⁻¹, ΔS = +200 J K⁻¹ mol⁻¹ Reaction 2: ΔH = −100 kJ mol⁻¹, ΔS = −200 J K⁻¹ mol⁻¹
Compare the feasibility of these two reactions at different temperatures. In your answer, use the Gibbs equation ΔG = ΔH − TΔS and explain how the sign of ΔG determines feasibility. Describe how changing temperature affects the feasibility of each reaction, referring to the magnitude and sign of the terms.
5 marks, so the mark scheme is looking for about 5 separate creditworthy points. Making the same point twice in different words earns it once.
Compare means: Give similarities or differences between two things, and say which side each point belongs to. Write each point as a pair, for example: A is X, whereas B is Y. Two separate descriptions rarely earn the marks.
Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.