For a reaction at $25\,^oC$,the enthalpy change $(\Delta H)$ and entropy change $(\Delta S)$ are $-11.7 \times 10^3\, J \, mol^{-1}$ and $-105 \, J \, mol^{-1} K^{-1}$ respectively. The reaction is:

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 $K$)

$A$ chemical reaction cannot occur at all if

For a reaction to be spontaneous at all temperatures,which of the following conditions must be satisfied?

In the conversion of limestone to lime,$CaCO_{3(s)} \rightarrow CaO_{(s)} + CO_{2(g)}$,the values of $\Delta H^{\circ}$ and $\Delta S^{\circ}$ are $+179.1 \ kJ \ mol^{-1}$ and $160.2 \ J \ K^{-1} \ mol^{-1}$ respectively at $298 \ K$ and $1 \ bar$. Assuming that $\Delta H^{\circ}$ and $\Delta S^{\circ}$ do not change with temperature,the temperature above which the conversion of limestone to lime will be spontaneous is ........... $K$.

$A$ minus sign of the free energy change denotes that