Rate of Reaction
The rate of the reaction will have the general look as shown. Assume that the rate law of the reaction is:
Rate = k [ P ]m [ Q ]n
The plan is to find out the actual values of m and n from the given data. Let's do it step by step.
Look at the given experimental data. If we compare Experiments 1 and 2, we can see that the concentration of Q is doubled in Experiment 2. But the concentration of P is kept constant. With these changes, we see the quadrupling of the rate. That means the exponent of Q is 2. At this point we can rewrite the rate law as follows:
Rate = k [ P ]m [ Q ]2
Now compare Experiments 2 and 3. Here the concentration of Q is kept constant, but the concentration of P is doubled. The rate is doubling because of this change. So the exponent of P is 1. We can now write the completed rate law of the reaction.
Rate = k [ P ] [ Q ]2