For the reaction $PCl_5 \to PCl_3 + Cl_2$,$\Delta H = 75 \ kJ \ mol^{-1}$ and $\Delta S = 120 \ J \ K^{-1} \ mol^{-1}$. At which temperature will the reaction be spontaneous? (in $K$)

For a reaction,$4 M (s) + n O_2 (g) \rightarrow 2 M_2 O_n (s)$,the free energy change is plotted as a function of temperature. The temperature below which the oxide is stable could be inferred from the plot as the point at which :

Calculate $\Delta H^{\circ}$ for a reaction at $298 \ K$ if $\Delta S^{\circ} = 120 \ J \ K^{-1}$ and $\Delta G^{\circ} = 28000 \ J$. (in $kJ$)

Gibbs free energy $G$,enthalpy $H$ and entropy $S$ are interrelated as in

For the given reaction: $H_{2(g)} + S_{(s)} \to H_2S_{(g)}$; $\Delta H_r = 100\, kJ/mol$ and $\Delta S_r = 400\, J/mol\cdot K$. The temperature at which the above reaction occurs reversibly is (Assuming $\Delta H_r$ and $\Delta S_r$ are independent of temperature) ..... $K$.

Which of the following conditions indicates the reaction is spontaneous?