Question

In the simple reaction $2A+B\to A_{2}B$, if the concentration of A is doubled and of B is halved, then the rate of reaction will

• A. increase by two times
• B. decrease by two times
• C. increase by four times
• D. remains the same

Answer 1

Answer: (A)

Reaction: $2A+B⟶A_{2}B$
Rate $=C[A{]}^2[B];C\to$ rate constant
let conc. of $A$ be $a_0\&$ that of $B$ be $b_0$
$\Rightarrow$ Rate $=c{a}_0^2{b}_0=k$ (say)
$A{u}^m$ to question, is concenctration of $a$ is doubled & $b$ is halved $\Rightarrow [A]=2a_0\&[B]=b_0/2.$
$\Rightarrow$ Rate $=c{\left(2a_0\right)}^2\left(b_{0/2}\right)$
$=2a_0{}^2{b}_{0}c=2k.$
$\Rightarrow$ on doing the following changes as said in question, rate of reaction doubles.