Write the formula relating the equilibrium constant $K$ and $\Delta G^{\circ}$.

For a system in equilibrium,$\Delta G = 0$ under conditions of constant:

$STATEMENT-1$: For every chemical reaction at equilibrium,standard Gibbs energy of reaction is zero. $STATEMENT-2$: At constant temperature and pressure,chemical reactions are spontaneous in the direction of decreasing Gibbs energy.

At $300 \ K$,for the reaction $PCl_{5(g)} \rightleftharpoons PCl_{3(g)} + Cl_{2(g)}$,the equilibrium constant $K_p = 1.8 \times 10^{-7}$. Calculate its standard Gibbs free energy change $\Delta G^0$.

For a homogeneous gaseous reaction,the equilibrium constant $K_p$ is $10^{-8}$. The standard Gibbs free energy change for the reaction is ........... $kcal$. $(R = 2.0 \, cal \, K^{-1} \, mol^{-1}, T = 298 \, K)$

The $\Delta G^o$ for the reaction $X + Y \rightleftharpoons Z$ is $-4.606 \ kcal$. The value of the equilibrium constant of the reaction at $227 \ ^oC$ is $(R = 2.0 \ cal \ mol^{-1} K^{-1})$.