question_answer 1)

  Write a relation between \[\Delta G\] and Q and define the meaning of each term and answer the following: (a) Why a reaction proceeds forward when Q < K and no net reaction occurs when \[Q=K?\] (b) Explain the effect of increase in pressure in terms of the reaction quotient Q for the reaction: \[CO(g)+3{{H}_{2}}(g)\underset{{}}{\leftrightarrows}C{{H}_{4}}(g)+{{H}_{2}}O(l)\]

Answer:

  We know, \[\Delta G=\Delta {{G}^{o}}+RT{{\log }_{e}}Q\,\,\,\,\,\,\,\,\,\,\,\,.....(i)\] where\[\Delta G\] = Free energy change \[\Delta {{G}^{o}}\] = Standard free energy change Q = Reaction Quotient At equilibrium, \[\Delta G=0\] and Q = K (equilibrium constant) \[\therefore \]\[\Delta {{G}^{o}}=-RT{{\log }_{e}}K\,\,\,\,\,\,\,\,\,\,\,......(ii)\] from eqns. (i) and (ii) \[\Delta G=-RT{{\log }_{e}}K+RT{{\log }_{e}}Q\] \[\Delta G=RT{{\log }_{e}}\left( \frac{Q}{K} \right)\] ·         When Q < K, \[\Delta G\] will be negative and reaction will spontaneous in forward direction. ·         When Q = K, \[\Delta G=0\]and reaction will be at equilibrium. When pressure is increased, the given reaction will proceed in forward direction where the number of gas moles are decreasing.