EntropyAQA A-Level Chemistry: Mind map

Exam questions on Entropy

1. A student discusses entropy using the three physical states of water. She considers how the disorder of the particles in ice, liquid water and steam changes as a sample of water is heated from below 0 °C to above 100 °C at constant pressure.
   Explain why the entropy of steam is greater than the entropy of liquid water at the same temperature.2 marks
2. Ammonia is made industrially in the Haber process: N₂(g) + 3H₂(g) → 2NH₃(g). Standard entropies (J K⁻¹ mol⁻¹): N₂(g) = 192; H₂(g) = 131; NH₃(g) = 193.
   Predict, with a reason, the sign of the entropy change for the reaction Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g).2 marks
3. Calcium carbonate decomposes on strong heating: CaCO₃(s) → CaO(s) + CO₂(g), ΔH = +178 kJ mol⁻¹. Standard entropies (J K⁻¹ mol⁻¹): CaCO₃(s) = 93; CaO(s) = 40; CO₂(g) = 214. Relative formula mass of CaCO₃ = 100.1.
   Calculate the entropy change for the decomposition of calcium carbonate. Include units.3 marks