What is the relationship between Gibbs free energy change,enthalpy change,and entropy change?

The values of $\Delta H$ and $\Delta S$ for the reaction,$C_{(graphite)} + CO_{2(g)} \rightarrow 2CO_{(g)}$ are $170 \ kJ$ and $170 \ J \ K^{-1}$ respectively. This reaction will be spontaneous at temperatures greater than ............ $K$.

The occurrence of a reaction is impossible if

$A$ reaction occurs spontaneously if

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 $K$)

State the criteria for a spontaneous process in terms of $\Delta G$ at constant pressure and temperature.