Question

For a reaction $A+2B\to C+D$, the following data were obtained.
Excpt. Initial concentration Initial Rate of formation of D
(moles ${litre}^{-1}$) ${litre}^{-1}{min}^{-1}$)
[A] [B]
1. $0.1$ $0.1$ $6.0\times {10}^{-3}$
2. $0.3$ $0.2$ $7.2\times {10}^{-2}$
3. $0.3$ $0.4$ $2.8\times {10}^{-1}$
4. $0.4$ $0.1$ $2.4\times {10}^{-2}$
The correct rate law expression will be:

• A. Rate=$k\left[A\right]\left[B\right]$
• B. Rate=$k\left[A\right][B{]}^2$
• C. Rate=$k\left[A{]}^2\right[B{]}^2$
• D. Rate=$k\left[A{]}^2\right[B]$

Answer 1

The correct option is B Rate=$k\left[A\right][B{]}^2$

In 2 and 3 (Keeping the Concentration of A constant), When the concentration of B is doubled, the rate gets quadrapled. So Order wrt [B] is 2

In 1 and 4 (Keeping the Concentration of B constant), When the concentration of A is quadrapled, the rate gets quadrapled. So Order wrt [A] is 1.

So Rate Law expression is,

$Rate=k\left[A\right][B{]}^2$