Chapter 9

Find the order of reaction for the rate expression rate \(=K[A][B]^{2 / 3}\). Also suggest the units of rate and rate constant for this expression.

For a reaction; \(3 A \longrightarrow\) Products, it is found that the rate of reaction becomes nine times if concentration of \(A\) is increased three times, calculate order of reaction.

The rate for the decomposition of \(\mathrm{NH}_{3}\) on platinum surface is zero order. What are the rate of production of \(\mathrm{N}_{2}\) and \(\mathrm{H}_{2}\) if \(K=2.5 \times 10^{-4}\) mol litre \(^{-1} \mathrm{~s}^{-1}\).

In a reaction; \(2 A \longrightarrow\) Products, the concentration of \(A\) decreases from \(0.5\) mol litre \(^{-1}\) to \(0.4\) mol litre \(^{-1}\) in 10 minutes. Calculate rate during this interval.

For the reaction; \(2 A+B+C \longrightarrow A_{2} B+C\) The rate \(=K[A][B]^{2}\) with \(K=2.0 \times 10^{-6} M^{-2} \mathrm{~s}^{-1} .\) Calculate the initial rate of the reaction when \([A]=0.1 M,[B]=0.2 M\) and \([C]=0.8 M\). If the rate of reverse reaction is negligible then calculate the rate of reaction after \([A]\) is reduced to \(0.06 M\).

A reaction is second order with respect to a reaction. How is the rate of reaction affected if the concentration of the reactant is : (a) doubled, (b) reduced to \(1 / 2 ?\)

A reaction is first order in \(A\) and second order in \(B\) : (i) Write differential rate equation. (ii) How is the rate affected when the concentration of \(B\) is tripled? (iii) How is the rate affected when the concentration of both \(A\) and \(B\) is doubled?

The experimental data for the reaction, \(2 A+B_{2} \longrightarrow 2 A B\) are as follows. Write probable rate expression; \(\begin{array}{ccc}{[A]} & {\left[B_{2}\right]} & \text { Rate } \times 10^{4} \\ \text { mol litre }^{-1} & \text { mol litre }^{-1} & \text { mol litre }^{-1} \text { sec }^{-1} \\ 0.50 & 0.50 & 1.6 \\ 0.50 & 1.00 & 3.2 \\ 1.00 & 1.00 & 3.2\end{array}\)

The decomposition of \(\mathrm{N}_{2} \mathrm{O}_{5}\) takes place according to I order as $$ 2 \mathrm{~N}_{2} \mathrm{O}_{5} \longrightarrow 4 \mathrm{NO}_{2}+\mathrm{O}_{2} $$ Calculate : (a) The rate constant, if instantaneous rate is \(1.4 \times 10^{-6}\) mol litre \(^{-1}\) \(\mathrm{sec}^{-1}\) when concentration of \(\mathrm{N}_{2} \mathrm{O}_{5}\) is \(0.04 \mathrm{M}\) (b) The rate of reaction when concentration of \(\mathrm{N}_{2} \mathrm{O}_{5}\) is \(1.20 \mathrm{M}\) (c) The concentration of \(\mathrm{N}_{2} \mathrm{O}_{5}\) when the rate of reaction will be \(2.45 \times 10^{-5} \mathrm{~mol}\) litre \(^{-1} \mathrm{sec}^{-\mathrm{i}}\).

Calculate the half life of a first order reaction from their rate constants given below : (a) \(200 \mathrm{~s}^{-1}\); (b) \(2 \mathrm{~min}^{-1}\); (c) 4 year \(^{-1}\).