NEET Chemistry Chemical Kinetics Questions Solved


A first order reaction complete 40% in 20 minutes. In how much time it is completed 90% of its original amount?

1. 45 min

2. 60 min 

3. 75 min

4. 90 min

(4) K = (2.303/t)log(a/a-x)

     when x = (40/100)a = 0.4a

     t = 20min

 K = (2.303/20)log(a/a-0.4a)

        =(2.303/20)log1/0.6

     K = 0.02554 min-1

     t = (2.303/0.02554)log(a/a-0.9a)

       =2.303/0.02554 log (1/0.1)

       =90.17 min

Difficulty Level:

  • 35%
  • 18%
  • 20%
  • 29%