Question

Thermal decomposition of $HCOOH$ is a first order reaction and the rate constant at T(K) is $4.606 \times 10^{-3}\, s^{-1}$. The time required to decompose $90\%$ of initial quantity of $HCOOH$ at $T(K)$ in seconds is

• A. 100
• B. 500
• C. 1000
• D. 50

Answer 1

Answer: (B)

500

Answer 2

First order reaction $K =\frac{2.303}{t} \log \frac{A_{0}}{A}$ Given, $K =4.606 \times 10^{-3} s ^{-1}$ $A=90 \%, A_{0}=$ Initial quantity $=100 \%$ $t=\frac{2.303}{4.606 \times 10^{-3}} \log \frac{1}{1-9}$ $t=500\, s$