Question

During the kinetic study of the reaction, $2A+B\to C+D$ following results were obtained.

Run	[A] in M	[B] in M	Iniitial rate of formation of D in $M{s}^{-1}$
I	0.1	0.1	$6.0\times {10}^{-3}$
II	0.3	0.2	$7.2\times {10}^{-2}$
III	0.3	0.4	$2.88\times {10}^{-1}$
IV	0.4	0.1	$2.40\times {10}^{-2}$

On the basis of above data which one is correct?

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

Answer 1

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

In Exp 1 and 4 ( Keeping the Conc. of [B] constant), when the concentration of A is quadrapled, the rate is also quadrapled. So Order with respect to A is 1

In Exp 2 and 3 ( Keeping the Conc. of [A] constant), when the concentration of B is doubled, the rate is quadrapled. So Order with respect to B is 2.

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