Question

In a pseudo first order hydrolysis of ester in water, the following results were obtained.

t/s	0	30	60	90
Ester/mol $L^{-1}$	0.55	0.31	0.17	0.085

What will be the average rate of reaction between the time interval $30$ to $60$ seconds?

• A. $1.91\times10^{-2}$ $s^{-1}$
• B. $4.67\times10^{-3} mol L^{-1} s^{-1}$
• C. $1.98\times10^{-3}$ $s^{-1}$
• D. $2.07\times10^{-2}$ $s^{-1}$

Answer 1

Answer: (B)

Average rate during the time interval $30-60 \,s$.
Rate=$-\frac{C_{2}-C_{1}}{t_{2}-t_{1}}$ $=-\frac{\left(0.17-0.31\right)}{60-30}$ $=\frac{0.41}{30}$
$=4.67\times10^{-3}$ $mol\,L^{-1}$ $s^{-1}$