Question

The rate constant for an isomerisation reaction, $A\to B$ is $4.5\times {10}^{-3}mi{n}^{-1}$. If the initial concentration of A is 1 M, the rate of the reaction after 1 hr will be:

• A. $3.4354\times {10}^{-3}$
• B. $4.4554\times {10}^{-3}$
• C. $5.4364\times {10}^{-3}$
• D. None of these

Answer 1

Answer: (A)

$3.4354\times {10}^{-3}$

$\underset{[A{]}_0=1M}{A\to B}K=4.5\times {10}^{-3}mi{n}^{-1}$
For Ist order reaction, $K=\frac{2.303}{t}log\frac{a}{(a-x)}$ at $t=60min$
$4.5\times {10}^{-3}=\frac{2.303}{60}lo{g}_{10}\frac{1}{(a-x)}$
$\therefore (a-x)=0.7634$
Thus, rate after 60 minute $=K(a-x)$
$=4.5\times {10}^{-3}\times 0.7634$
$=3.4354\times {10}^{-3}$