Chemistry-Rate Law Problem?

Question

The rate of the reaction CO2(g) + H2(g) → H2O(g) + CO(g) was determined in three experiments at 650 K. The results are given in the following table:

Experiment 1- [CO2] in mM=20.0, [H2] in mM=12.0, rate in mM/min= 2.3

Experiment 2- [CO2] in mM=20.0, [H2] in mM=24.0, rate in mM/min= 4.6

Experiment 3- [CO2] in mM=40.0, [H2] in mM=12.0, rate in mM/min= 4.6

A) What is the rate law for this reaction?

B) What is the rate constant k?

C) What would be the rate if starting concentrations were [CO2]=40.0 mM and [H2]=24.0 mM

Update:

Thanks!

Answer 1

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A) by comparing experiments 1 and 2, you see that doubling [H2] doubles the rate. So, the reaction is first order with respect to [H2]. By comparing reactions 1 and 3, you see that doubling [CO2] also doubles the rate, so the reaction is also first order with respect to [CO2]. Therefore, the rate law is:

Rate = k[CO2][H2]

B) To calculate the value of k, just plug in everything from one of the experiments into the rate law and solve for k:

2.3 mM/min = k(20.0)(12.0)

k = 9.6X10^-3 mM^-1 min^-1

C) Again, just plug what you know into the rate law and calculate the rate:

Rate = 9.6X10^-3 mM^-1 min^-1 (40.0 mM) (24.0 mM)

Rate = 9.2 mM/min