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. Suppose N_(2)O_(4)(g) is enclosed in a cylinder fitted with a movable piston which attains the following equilibrium N_(2)O_4)(g) hArr 2NO_(2)(g) Given that for the 10 atmosphere pressure of the equilibrium mixture,the content of NO_(2) is 8xx1^(5)ppm. if the piston of cylinder is moved upward in such a manner so that the volume of the gaseous mixture becomes double, then what will be new ppm of NO_(2)(g) in the cylinder ?( Assuming that the temperature of the cylinder remains constant )