Which of the following processes are expected to be spontaneous at low temperature and non-spontaneo — Thermodynamics and Thermochemistry Chemistry Question

💡 Solution & Explanation

For spontaneous at low T and non-spontaneous at high T: need Δ H < 0 and Δ S < 0. A: Dissociation is endothermic (Δ H>0) and increases entropy (Δ S>0) — spontaneous at high T, not low T (incorrect). B and C: Combination to form water is highly exothermic (Δ H<0) and reduces gas moles (Δ S<0) — spontaneous at low T, non-spontaneous at high T (correct). D: Freezing is exothermic (Δ H<0) and decreases disorder (Δ S<0) — spontaneous below 273 K (low T), non-spontaneous above 273 K (correct).