For the reaction: A(g) → 2B(g) + C(g), the rate constant is 1.386 × 10^-3 s^-1. The reaction is performed at constant pressure and temperature, starting with only 'A'. The initial concentration of 'A'

Question

For the reaction: A(g) → 2B(g) + C(g), the rate constant is 1.386 × 10^-3 s^-1. The reaction is performed at constant pressure and temperature, starting with only 'A'. The initial concentration of 'A' was 0.1 M. The concentration of 'A' (in millimole per litre) after 500 s from the start of reaction is

Prashant Kotian · Accepted Answer

Correct answer: 0025. The half-life is t1/2 = 0.693 / (1.386 × 10^-3) = 500 s. So exactly one half-life has passed. Moles of A halve to n0/2, while n0 moles of B and n0/2 moles of C are produced. Total moles = 2n0. Since P and T are constant, Volume doubles to 2V0. Final concentration of A = (n0/2) / (2V0) = 0.25 × (n0/V0) = 0.25 × 0.1 M = 0.025 M = 25 mM. Therefore, correct answer is 0025.

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