Experimental rate data was collected for the following reaction. Determine the rate law.

2 NO + Cl2 2 NOCl

Expt.

[NO]

[Cl2]

Initial rate

1

0.010

0.010

1.210-4

2

0.010

0.020

2.310-4

3

0.020

0.020

9.610-4

The rate law will have the form            Rate = k [NO]x [Cl2]y.

we have an equation with three unknowns (k, x, and y); Rate is measured. We need at least three different measurements of Rate to be able to solve this problem.

1 1.2 10–4 = k  0.010x 0.010y
2 2.3 10–4 = k  0.010x 0.020y
3 9.6 10–4 = k  0.020x 0.020y

Now, we can solve for the three unknowns,

divide equations 2/1

Divide equations 3/2

We now know both x and y. We can solve for k using any one of the three equations.