The reaction rates of many spontaneous reactions are actually very slow. Which of these statements is the best explanation for this observation?

a. Kp for the reaction is less than one

b. ÎG° for the reaction is positive

c. The entropy change (ÎS) is negative B)

d. The activation energy of the reaction is large.

e. Such reactions are endothermic

the correct answer is d (The activation energy of the reaction is large)

Explanation:

the Kp represents an equilibrium constant in terms of partial pressures. The fact that is less than 1 represents that the equilibrium favours reactants compared to products (the extent of the reaction), but it does not speak about reaction rates.

If the ΔG of the reaction is positive then they would not be spontaneous, in contradiction with the problem's statement.

If the entropy change is negative or the reaction is endothermic, then it means that they contribute positively to the ΔG. But more positive ΔG does not necessarily means slower reaction rates

Nevertheless, the activation energy represents the energy barrier against the formation of products. When higher the activation energy, the reaction rates are slower. Thus the correct answer is d