Question

The rate constant of the reaction $2N_2O_5 \rightarrow 4NO_2 + O_2$ at $300\,K$ is $3 \times 10^{-5}\,s^{-1}$. If the rate of the reaction at the same temperature is $2.4 \times 10^{-5}\, mol\, dm^{-3}\, s^{-1}$, then the molar concentration of $N_2O_5$ is

• A. 0.4 M
• B. 0.8 M
• C. 0.04 M
• D. 0.008 M
• E. 0.08 M

Answer 1

Answer: (B)

Given,

$k($ rate constant $)=3 \times 10^{-5} s ^{-1}$ which

indicates that reaction is of first order. $\left(: \cdot\right.$ unit is $\left.s^{-1}\right)$

$\therefore r$ (rate ofreaction) $=k$ [concentration] $^{1}$

$\therefore $ [ concentration ]$=\frac{r}{k}$

[ concentration ]$=\frac{2.4 \times 10^{-5}}{3.0 \times 10^{-5}}=0.8\, M $