In a chemical reaction $A$ is converted into $B$. The rates of reaction, starting with initial…

In a chemical reaction $A$ is converted into $B$. The rates of reaction, starting with initial concentrations of $A$ as $2 \times 10^{-3} \mathrm{M}$ and $1 \times 10^{-3}$ $\mathrm{M}$, are equal to $2.40 \times 10^{-4} \mathrm{Ms}^{-1}$ and $0.60 \times 10^{-4} \mathrm{Ms}^{-1}$ respectively. The order of reaction with respect to reactant $A$ will be
  1. 0
  2. $1.5$
  3. 1
  4. 2

Solution

$A \longrightarrow B$ Initial concentration Rate of reaction $ \begin{array}{ll} 2 \times 10^{-3} \mathrm{M} & 2.40 \times 10^{-4} \mathrm{Ms}^{-1} \\ 1 \times 10^{-3} \mathrm{M} & 0.60 \times 10^{-4} \mathrm{Ms}^{-1} \end{array} $ rate of reaction $ r=k[A]^x $ where $x=$ order of reaction hence $ \begin{aligned} & 2.40 \times 10^{-4}=k\left[2 \times 10^{-3}\right]^x \\ & 0.60 \times 10^{-4}=k\left[1 \times 10^{-3}\right]^x \end{aligned} $ on dividing eqn.(i) from eqn. (ii) we get $4=(2)^x$ $\therefore \quad x=2$ i.e. order of reaction $=2$

Asked in: JEE Main 2012 (12 May Online)

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