Question

Cyclopropane rearranges to form propene

This follows first order kinetics. The rate constant is $2.714\times10^{-3}$ $sec^{-1}$. The initial concentration of cyclopropane is $0.29$ $M^{\cdot}.$ What will be the concentration of cyclopropane after $100$ sec?

• A. $0.035 \,M$
• B. $0.22 \,M$
• C. $0.145 \,M$
• D. $0.0018\, M$

Answer 1

Answer: (B)

$k=\frac{2.303}{t} log$ $\frac{a}{\left(a-x\right)}$
$\left(a-x\right)$ is the concentration left after $100$ sec.
$2.7\times10^{-3}$ $=\frac{2.303}{100}log$ $\frac{0.29}{\left(a-x\right)}$
$\Rightarrow $ $\frac{0.27}{2.303}=log$ $\frac{0.29}{\left(a-x\right)}$
$\Rightarrow $ $0.117=log$ $\frac{0.29}{\left(a-x\right)}$
$\Rightarrow $ $\left(a-x\right)=0.22 M$