The reaction which is in dynamic equilibrium, ensured us, that the reaction is reversible . But if that the reaction is in equilibrium. The reaction quotient predict either the reversiblereaction is in equilibrium or tries to achieve equilibrium. In those reactions which have not achieved equilibrium, we obtain reaction quotient Q_(c) in place of equilibrium constant (K_(c)) by substituting the concentration of reactant and product at the time, at whih we have to calculate the value of Q_(c) . To determine the direction at which the net reaction will proceed to achieve equilibrium, we compare values of Q_(c) and K_(c). The three possible cases are shown as comparison of K_(c) and Q_(c) in the following figures. Change in Gibbs free energy, i.e., Delta G is the driving force of any reaction. For spontaneous reaction , Delta G =-ve For non-spontaneous reaction , Delta G=+ve For reaction at equilibrium , Delta G =0 Thermodynamically, we know that Delta G= Delta G^(@)+ RTln Q, where Q is reaction quotient and Delta G^(@)= change in Gibbs energy at standard condition. For equilibrium A(g) hArr B(g) (K_(eq) =1.732) If the pressure of the system [varied by introducing a stream of A (g) and B (g) is representedby the curve at constant temperature T. If A and B are enclosed in the cylinder and piston of the cylinder be moved downward so that volume of cylinder becomes half, then what will be the effect in K_(c) at constant temeprature ?