Methods of Determining Reaction Order - Practice Questions & MCQ

It is used when the rate law involves only one concentration term.

 
or 

For two different concentrations, we have:

On taking logarithms on both sides, we get:

Hence,

Here,  n is the order of the reaction.

Here graphs are plotted between rate and concentration to find the order of the reaction.

Plots of Rate vs Concentration

If the data for time(t) and [A] is given then this method is applicable. Thus follows the steps given below to find the order of reaction by using the integrated rate law method.

• Check for First Order: 
  1. Use the formula given below to find out the two values of k as k₁ and k₂.
     
  2. If these two values k₁ and k₂ are same, then this given reaction is of first-order. But if k₁≠ k₂, then check for zero-order.
• Check for Zero-Order:
  1. Use the formula given below to find out the two values of k as k₁ and k₂.
     
  2. Again, if these two values k₁ and k₂ are same, then this given reaction is of zero-order. But if k₁≠ k₂, then check for second-order.
• Check for Third-Order:
  1. Use the formula given below to find out the two values of k as k₁ and k₂.
     
  2. Further, if these two values k₁ and k₂ are same, then this given reaction is of second-order. But if k₁≠ k₂, then check for third-order and so on.