Calculation Of Equilibrium Constant

How can Nernst equation be applied in calculating the equilibrium constant for any cell reaction ?

3 g mol of phosphorus is heated in a flask of 4 L volume. At equilibrium, it dissociates to give 40% of phosphorus trichloride and chlorine. Calculate the equilibrium constant.

For an equilibrium reaction, the rate constants for the forward and the backward reaction are 2.38xx10^(-4) and 8.15xx10^(-5) , respectively. Calculate the equilibrium constant for the reaction.

1.5 mol of PCl_(5) are heated at constant temperature in a closed vessel of 4 L capacity. At the equilibrium point, PCl_(5) is 35% dissociated into PCl_(3) and Cl_(2) . Calculate the equilibrium constant.