For which of the following process Δ S° is positive? — Thermodynamics and Thermochemistry Chemistry Question

💡 Solution & Explanation

A: Dissolution of $NH_4NO_3$(s) in water increases disorder (ions disperse in solvent) — Δ S > 0. B: Gas expansion increases available volume and randomness — Δ S > 0. C: Decomposition 2$HgO$(s) → 2Hg(l) + $O_2$(g) produces gaseous $O_2$, significantly increasing entropy — Δ S > 0. D: Rusting 4Fe(s) + 3$O_2$(g) → 2$Fe_2O_3$(s) consumes $O_2$ gas, reducing randomness — Δ S < 0.