General Chem Determine order of rxn with respect to b from in below

Question

Inital [A] (M) Inital [B] (M) Inital Rate of Formation of C (mol/L*min)

2.5 *10^6 3 *10^-4 5 *10^-3

5 *10^-6 3* 10^-4 1*10 ^-2

1 *10^-5 9 *10^-4 1.8 *10 ^-1

Answer 1

i dont know how to do this!

Answer 2

Let

[C]' = k * [A]^x * [B]^y

be the general formula for the rate of formation of C based on the concentrations of A and B.

From line a) to b), you double the concentration of A, keeping that of B constant, and you notice that the rate doubles. Hence x=1.

From line b) to c), you again double [A], and increase [B] three-fold, noticing that the rate rises 18-fold. So (canceling unnecessary terms) you have to solve

18 = 2^1 * 3^y

which yields y=2.

Ie the rxn is 1st order in A, 2nd order in B.