Question

Suppose a first-order reaction has a half life of 10.0 minutes. How much time is required for this reaction to be 75.0% complete. Express your answer in minutes.

Answer 1

Half life of a first order reaction is expressed by [A]t_1/2 = [A_o]/2. In other word, time required for the completeion of 50% of the initial concentration is called the half life. Here the t_1/2 = 10 minutes.

So, 50% will be complete after 10 minutes.

After another 10 minutes 50% of this remaining 50% amount will be converted which is equal to 25% of the initial concentration.

Thus 20 minutes will be required to complete 75% of the reaction.