What is the rate equation for this reaction?

Question

2NO+I2=>2NOI

TRIAL 1

initial concentration of NO(M)

1.5

initial concentration of I2(M)

1.0

instantaneous reaction rate (M/s)

1.25

TRIAL 2

initial concentration of NO(M)

1.5

initial concentration of I2(M)

2.0

instantaneous reaction rate (M/s)

2.50

TRIAL 3

initial concentration of NO(M)

3.0

initial concentration of I2(M)

2.0

instantaneous reaction rate (M/s)

10.0

Answer 1

To write the rate equation for the reaction we want to find the order with respect to each of the reactants.

Looking at NO first, we compare Trial 2 to Trial 3 where the [NO] is doubled but [I₂] remains constant. We see that the rate goes from 2.50 to 10 so it increased 4x. Thus the reaction is SECOND ORDER IN NO.

Looking at I2, we compare Trial 1 to Trial 2 where the [I₂] is doubled but [NO] remains constant. We see that the rate goes from 1.25 to 2.50 so it doubled. Thus the reaction is FIRST ORDER IN I₂.

The rate equation is...

Rate = k[NO]²[I₂]