Select the correct equilibrium constant expression, Kc for the following reversible reaction. Ce4+(aq) + Fe2+(aq) → Ce3+(aq) + Fe3+(aq)
Correct answer: A. Kc = [Ce3+][Fe3+]/[Ce4+][Fe2+]
- A. Kc = [Ce3+][Fe3+]/[Ce4+][Fe2+]
- B. Kc = [Ce3+][Fe2+]/[Ce4+][Fe3+]
- C. Kc = [Ce4+][Fe3+]/[Ce3+][Fe2+]
- D. Kc = [Ce3+][Fe2+][Ce4+][Fe3+]
Explanation
The correct equilibrium constant expression, Kc, for the given reaction is Kc = [Ce3+][Fe3+]/[Ce4+][Fe2+]. This expression is derived by dividing the product of the concentrations of the products (Ce3+ and Fe3+) by the product of the concentrations of the reactants (Ce4+ and Fe2+). Each concentration is raised to the power of its respective stoichiometric coefficient, which in this case are all 1, so they do not alter the expression. Option A correctly reflects these principles. The other options either incorrectly swap reactants and products or fail to apply the division necessary to form the equilibrium constant expression.
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About Reversible Reactions
A reversible reaction proceeds in both forward and backward directions, so reactants and products continue changing until dynamic equilibrium is established. The topic covers the meaning of equilibrium, the equality of forward and reverse rates, and how concentration, pressure and temperature disturb equilibrium, which is separate from the rate at which equilibrium is reached.
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