Question

A first order reaction A $\to$ products has k$=$6.93 $mi{n}^{-1}$ . If 90% of first order reaction B $\to$ products is completed in the time taken by 50% of the first reaction, what is the rate constant for the second reaction?

• A. 0.76 min
• B. 23.03min
• C. 5.6 min
• D. 6.7 min

Answer 1

The correct option is B 23.03min

$A\to prod.$
$K=6.93$
$t_{{}^1{/}_2}=\frac{ln2}{6.93}$
$=0.100$
$NowforB\to prod.K=\frac{1}{0.100}ln\left[\frac{a}{a-.9}\right]$
$K=\frac{ln10}{0.1}$
$=23.02min$