Question

The data for the reaction $A+B\to C$ is:

Exp.	${\left[A\right]}_0$	${\left[B\right]}_0$	initial rate
1	0.012	0.035	0.10
2	0.024	0.035	0.80
3	0.012	0.070	0.10
4	0.024	0.070	0.80

• A. $r=k{\left[B\right]}^3$
• B. $r=k{\left[A\right]}^3$
• C. $r=k\left[A\right]{\left[B\right]}^4$
• D. $r=k{\left[A\right]}^3{\left[B\right]}^2$

Answer 1

Answer: (B)

$r=k{\left[A\right]}^3$

In Exp 1 and 3 (Keeping the Concentration of [A] constant) , When the concentration of ${\left[B\right]}_0$ is doubled, there is no change in the rate.

So Order wrt [B] is 0

In Exp 1 and 2 (Keeping the Concentration of [B] constant) , When the concentration of ${\left[A\right]}_0$ is doubled, the rate becomes eight times.

So Order wrt [A] is 3.

So the rate equation is,

$r=k[A{]}^3$