Question

Consider the reaction 2A + B →products, when the concentration of A alone was doubled, the half-life of the reaction did not change. When the concentration of B alone was doubled, the rate was not altered. The unit of rate constant for this reaction is

• (A) s ^{− 1}
• (B) L mol ^{− 1} s ^{− 1}
• (C) mol L ^{− 1} s ^{− 1}
• (D) mol ^{− 2} L5 s ^{− 1}

Answer 1

The Correct Option is A

Explanation:
$2A+B\to$ ProductLet rate of reaction, $r=k[A{]}^{x_1}[B{]}^{x_2}$When concentration of $\mathrm{B}$ doubled rate does not changesSo, $r_1=r_2$$\Rightarrow k[A{]}^{x_1}[B{]}^{x_2}=k[A{]}^{x_1}[2B{]}^{x_2}$$\Rightarrow [B{]}^{x_2}=[2B{]}^{x_2}$$\Rightarrow x_2=0$so rate, $r=k[A{]}^{x_1}$Now when Concentration of A doubled half life does not changeit means reaction is first order so $x_1=1$and $r=k\{A]$order of reaction $=1$so unit of rate constant $=s^{-1}$