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:

1. 70

2. –33

3. 33

4. –70

For the oxidation of iron,

4Fe(s) + 3O₂ (g) →  2Fe₂O₃ (s)
entropy change is -549.4 JK^-1 mol^-1 at 298 K.

(${∆}_r{H}^{\Theta }$ for this reaction is $-1648 \times {10}^3 J mo{l}^{-1}$)

The reaction is:

1. Spontaneous reaction

2. Non-spontaneous reaction

3. Reaction is an equilibrium

4. Cannot predict