Substance A decomposes by a first-order reaction. Starting initially with [A] = 2.00 M, after 150 min [A] = 0.50 M. For this reaction what is t1/2?

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Quizplus · Accepted Answer

For a first-order reaction, the half-life (t1/2) is constant and can be calculated using the formula t1/2 = 0.693/k. The rate constant k can be determined using the formula ln([A]0/[A]) = kt. Substituting the given values, ln(2.00/0.50) = k(150 min), we find k = 0.01386 min^-1. Thus, t1/2 = 0.693/0.01386 = 50 min. However, since the concentration decreases from 2.00 M to 0.50 M in 150 min, it indicates two half-lives have passed, so t1/2 = 150 min / 2 = 75.0 min.

Substance a Decomposes by a First-Order Reaction