Question

A reaction is started with both reactants and products and proceeds in the reverse direction to reach equilibrium. Which of the following statements best describes why the reaction proceeds in the reverse direction?
A) The initial rate of the reverse reaction is greater than the initial rate of the forward reaction.
B) The rate constant of the reverse reaction is greater than the rate constant of the forward reaction.
C) The activation energy of the reverse reaction is less than the activation energy of the forward reaction.
D) The reactants are lower in energy than the products.

Answer 1

Answer:

Option A

Explanation:

A) Yes. The reaction reaches equilibrium when the rate of reaction of the reverse reaction is equal to the rate of the forward reaction , then the only cause for the reverse reaction to be favoured is that the initial rate of the reverse was greater than the forward one.

B) No. The rate constant of the reverse reaction can be greater than the forward one  but the rate also depends on concentrations, thus a reverse reaction with greater rate constant can result in the net reaction proceeding in the forward reaction, the reverse reaction or be at equilibrium depending on the concentrations or reactants and products

C) No. A lower activation energy means a higher rate constant , but a higher rate constant does not mean that the net reaction will proceed to the reactants ( see point B)

D) No. The energy changes determine conditions under thermodynamic equilibrium and therefore the net direction of the reaction will depend on the temperature and concentrations of reactants and products with respect to the equilibrium conditions.