If for a certain reaction ${∆}_{r}H$ is 30 kJ mol^–1 at 450 K, the value of ${∆}_{r}S$ (in JK^–1 mol^–1) for which the same reaction will be spontaneous at the same temperature is:

Find the nature of the oxidation of iron at 298 K:

4Fe(s) + 3O₂(g) → 2Fe₂O₃(s)

Given:

Δ_rH° = −1648 × 10³ J mol⁻¹
Δ_rS° = −549.4 J K⁻¹ mol⁻¹

1. Spontaneous reaction

2. Non-spontaneous reaction

3. Reaction is at equilibrium

4. The nature of the reaction cannot be predicted.