Question

A first order reaction has a half-life period of 69.3 sec. At $0.10M$ reactant concentration, rate will be:

• A. ${10}^{-3}M.se{c}^{-1}$
• B. ${10}^{-4}M.se{c}^{-1}$
• C. ${10}^{-2}M.se{c}^{-1}$
• D. None of these

Answer 1

The correct option is A ${10}^{-3}M.se{c}^{-1}$

Given that a first order reaction has a half-life period of $69.3$seconds.

$K=\frac{0.693}{t_{1/2}}=\frac{0.693}{69.3}={10}^{-2}{\sec }^{-1}$

Now,

$r=K\left[A\right]={10}^{-2}\times 0.1={10}^{-3}Mse{c}^{-1}$.