Chemistry related

Question

When equilibrium has been reached in the reaction

AE + CD →← CE + AD + x kJ

in which all substances are in solution,

(A) adding AE will increase the concentration of CE but not of AD.

(B) adding CD will increase the concentration of both AE and AD.

(C) heating will increase the concentration of both AE and CE.

(D) escape of some AD by volatilization will increase the concentration of CE.

(E) doubling the pressure will increase the concentration of CE.

Could you explain which answer/option is correct?

Answer 1

This is a question based on an understanding of LeChatelier's Principle. This principle essential says that when a system is at equilibrium, any stress that is placed on that system will be counteracting in an attempt to return to the original equilibrium condition. The correct answer is D.

AE + CD <==> CE + AD + heat (the kJ on the product side represents an exothermic reaction)

Here is an explanation for the answers to all options:

(A) adding AE will increase the concentration of CE but not of AD.

No. Adding AE will increase the concentrations of BOTH CE and AD (to reverse the change made)

B) adding CD will increase the concentration of both AE and AD.

No. Adding CD will increase AD and CE, but will decrease CD (to reverse the change made)

(C) heating will increase the concentration of both AE and CE.

No. Heating will increase AE, but will decrease CE (to reverse the change made)

(D) escape of some AD by volatilization will increase the concentration of CE.

YES. As AD decreases (by volatilization), CE will increase as reaction is pulled to left.

(E) doubling the pressure will increase the concentration of CE.

No. Pressure only affects equilibrium systems when gases are present. These are all aqueous.