Question

The reaction A + B → C has a ∆G'° of –20 kJ/mol at 25° C. Starting under standard conditions, one can predict that: A) at equilibrium, the concentration of B will exceed the concentration of A. B) at equilibrium, the concentration of C will be less than the concentration of A. C) at equilibrium, the concentration of C will be much greater than the concentration of A or B. D) C will rapidly break down to A + B. E) when A and B are mixed, the reaction will proceed rapidly toward formation of C.

Answer 1

Answer:

C) at equilibrium, the concentration of C will be much greater than the concentration of A or B.  

Explanation:

A + B ⇌ C; ΔG° = -20 kJ·mol⁻¹

If ΔG is negative, the reaction is spontaneous and position of equilibrium lies to the right, so the equilibrium concentration of C is much greater than that of A or B.

A) is wrong. The molar ratio of A:B is 1:1. If their initial concentrations are 1 mol·L⁻¹, their final concentrations will be equal.

B) is wrong. The position of equilibrium lies to the right, so the concentration of C will be much greater than that of A.

D) and E) are wrong. ΔG says nothing about the rate of a reaction. It deals with the spontaneity and position of equilibrium not the speed at which equilibrium is achieved.