Question

The value of rate constant for a reaction $A\to B$ is 0.0693 $mi{n}^{-1}$. If the initial concentration of A is 1.0 M, the half-life in minutes is:

• A. 10
• B. 20
• C. 40
• D. 5

Answer 1

The correct option is A 10

$t_{1/2}=\frac{0.693}{k}=\frac{0.693}{0.0693}$ = 10 min
$\Rightarrow$ Rate = k[A]
$=0.0693\times 1.0=0.0693mo{l}^{-1}{L}^{-1}mi{n}^{-1}$
$[Nowrate{]}_t$ = 30 min = k[ct]
$\Rightarrow c_t=\frac{c_0}{8}=\frac{1}{8}$
$\Rightarrow Rat{e}_t=30=0.0693\times \frac{1}{8}$
$=8.66\times {10}^{-3}mo{l}^{-1}{L}^{-1}mi{n}^{-1}$