Suppose NaOH is added to the following system when it is at equilibrium. NH_3(aq

Question

Suppose NaOH is added to the following system when it is at equilibrium. NH_3(aq) + H_2 O(l) NH_4^+ (aq) + OH^- (aq) In which direction will the reaction shift after the NaOH is added? Will this stress increase or decrease the value of the reaction quotient Justify your answer. Will the rate of the forward reaction exceed the rate of the reverse before equilibrium is re-established? Justify your answer. When equilibrium is re-established will the rate of the forward reaction exceed the rate of the reverse reaction? Justify your answer. Suppose additional CO(g) is added to the following system when it is at equilibrium? CO(g) + PbO(s) CO_2(g) + Pb(s) In which direction will the reaction shift after the CO is added? Will this stress increase or decrease the value of the reaction quotient, Justify your answer. Will the rate of the forward reaction exceed the rate of the reverse before equilibrium is re-established? Justify your answer. When equilibrium is re-established will Q be greater than, equal to or than K? Justify your answer.

Explanation / Answer

Q4)The reaction is NH3 + H2O <-----> NH4+  + OH-

a) When NaOH is added to this equilibrium, due to common ion effect the dissociation of weak base NH3 further suppresses, that is the reaction goes backward.

The direction of equilibrium shifts backwards.

b) At this stage as the dissociationis less the reaction quotient, which has the same form as Kc , decreases.

The reactoion quotient is Q = [NH4+][OH-] /[NH3][H2O] decreases

c)At equilibrium the reaction quotient = equilibrium constant.

Now since th eQ< K, the rate of forward reaction increases before the new equilibrium establishes.

Thus before the new equilirium the rate of forward reaction is more than rate of backward reaction.

d) Once the new equilibrium is attained the rate of forward reaction = the rate of backward reaction.

5) The reaction is CO + PbO(s) <-----> CO2 + Pb

a) When CO is added to this equilibrium , the reactant is added so the equilibrium shifts right side or the rate of forward reaction increases.

b) This stress is increasing the rate of forward reaction, thus the reaction quotient value increases.

c) yes. The rate of forward reaction exceeds the rate of reverse reaction, befre the equilibrium is re established.

d)When the equilibrium is re established , Q= K as the K value does not depend on the oncentrations of reactants and products , but changes only with temperature.

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