Question

At a certain temperature, the rate constant of a first-order reaction is $1.40$ min${}^{-1}$. Find its half-life.

• A. $0.495min$
• B. $0.655min$
• C. $0.565min$
• D. $0.785min$

Answer 1

The correct option is A $0.495min$

For first order reactions the half life is given by:

$t_{\frac{1}{2}}=\frac{0.693}{k}$

$t_{\frac{1}{2}}=\frac{0.693}{1.40}=0.495$ min

Hence, the correct option is $\text{A}$.