Entropy and Spontaneity (Additional Higher Level) · Paper 1 — Free Chemistry SL Practice Questions

The decomposition of calcium carbonate, $\text{CaCO}_3\text{(s)} \rightarrow \text{CaO(s)} + \text{CO}_2\text{(g)}$, is non-spontaneous at 298 K but becomes spontaneous at 1200 K. Which statement correctly explains this change in spontaneity?

For the reaction $\text{N}_2\text{(g)} + 3\text{H}_2\text{(g)} \rightleftharpoons 2\text{NH}_3\text{(g)}$, the standard enthalpy and entropy changes are $\Delta H^\circ = -92 \text{ kJ mol}^{-1}$ and $\Delta S^\circ = -198 \text{ J K}^{-1}\text{mol}^{-1}$. Which statement correctly describes the spontaneity of this reaction at 298 K and 500 K?

In the Haber process, $\text{N}_2\text{(g)} + 3\text{H}_2\text{(g)} \rightleftharpoons 2\text{NH}_3\text{(g)}$, the forward reaction is exothermic. Which statement correctly describes the entropy change of the system and the temperature conditions under which the forward reaction is thermodynamically spontaneous?

When ammonium nitrate, $\text{NH}_4\text{NO}_3\text{(s)}$, dissolves in water, the solution temperature drops noticeably. The dissolution is spontaneous at room temperature. Which statement correctly identifies $\Delta H$ and $\Delta S$ for the dissolution and thermodynamic reason for spontaneity?