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 reversible reaction 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^(@)+ RT ln 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 represented by the curve at constant temperature T. Suppose the equilibrium system `N_(2)O_(4)(g) hArr 2NO_(2)(g)` `N_(2)O_(4)(g)` is in a cylinder fitted with a movable piston . Which of the following statements is correct ?A. If piston is pushed downwards at constant temperature, `Q_(c) gt K_(c)` and the direction shifts in the left direction.B. If pistaon is pushed downwards at constant temperature `Q_(c) gt K_(c)` and the reaction shifts in the right direction.C. If piston is released at constant temperature , `Q _(c) gt K_(c)` and the reaction shifts in the left direction.D. If piston is released at a constant temperature, and the reaction shifts in the right direction.