The acidic hydrolysis of ethyl acetate in aqueous solution is first order with respect to ethyl acetate. Upon varying the pH of solution, the first-order rate constant varies as follows: pH 3 (K1 = 1.

Question

The acidic hydrolysis of ethyl acetate in aqueous solution is first order with respect to ethyl acetate. Upon varying the pH of solution, the first-order rate constant varies as follows: pH 3 (K1 = 1.0 × 10^-3 s^-1), pH 2 (K1 = 10 × 10^-3 s^-1), pH 1 (K1 = 100 × 10^-3 s^-1). If the order of reaction with respect to H^+ is x and the value of the rate constant (in M^-1 s^-1) is y, then the value of (x + y) is

Prashant Kotian · Accepted Answer

Correct answer: 2. Decreasing pH by 1 increases [H^+] by a factor of 10. The rate constant K1 also increases by a factor of 10. Thus, x = 1. K1 = y[H^+]^x. At pH = 3, [H^+] = 10^-3 M. Substituting gives 1.0 × 10^-3 = y(10^-3)^1, so y = 1. The value of (x + y) = 1 + 1 = 2. Therefore, correct answer is 2.

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