A reaction is second order with respect to a reactant. How is the rate of reaction affected if the concentration of the reactant is 

$(i)$ doubled

$(ii)$ reduced to half $?$

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Let the concentration of the reactant be $[ A ]=a$

Rate of reaction, $R=k[A]^{2}$

$=k a^{2}$

$(i)$ If the concentration of the reactant is doubled, i.e. $[ A ]=2 a$, then the rate of the reaction would be

$R ^{\prime}=k(2 a)^{2}$

$=4 ka ^{2}$

$=4 R$

Therefore, the rate of the reaction would increase by $4$ times.

$(ii)$ If the concentration of the reactant is reduced to half, i.e. $[ A ]=\frac{1}{2} a$
the reaction would be

$R ^{\prime \prime}=k\left(\frac{1}{2} a\right)^{2}$

$=\frac{1}{4} k a$

$=\frac{1}{4} R$

Therefore, the rate of the reaction would be reduced to ${\frac{1}{4}^{th}}$

Similar Questions

The rate of the reaction becomes twice when the concentration of reactant becomes $8$ times then the order of the reaction is

In a reaction between $A$ and $B$, the initial rate of reaction $\left(r_{0}\right)$ was measured for different initial concentrations of $A$ and $B$ as given below:

$A/mol\,\,{L^{ - 1}}$ $0.20$ $0.20$ $0.40$
$B/mol\,\,{L^{ - 1}}$ $0.30$ $0.10$ $0.05$
${r_0}/mol\,\,{L^{ - 1}}\,\,{s^{ - 1}}$ $5.07 \times 10^{-5}$ $5.07 \times 10^{-5}$ $1.43 \times 10^{-4}$

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$2 \mathrm{H}_{2}(\mathrm{g})+2 \mathrm{NO}(\mathrm{g}) \rightarrow \mathrm{N}_{2}(\mathrm{g})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{g})$

the observed rate expression is, rate $=\mathrm{k}_{\mathrm{f}}[\mathrm{NO}]^{2}\left[\mathrm{H}_{2}\right] .$ The rate expression of the reverse reaction is

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