Question

A sample of a radioactive substance undergoes 80% decomposition in 345 minutes its half life is

Answer 1

Answer:

Let the initial concentration of radioactive substance be 100.

Then, the concentration left is =100-80

                                                     = 20

log 5=0.7

NOTE- DECOMPOSITION OF RADIOACTIVE SUBSTANCE IS THE FIRST ORDER REACTION.

SOLUTION-

t=2.303/k*logAi/Af

              345=2.303/k*log100/20

                k=2.303/345*log5

                k= 2.303/345*0.7

                k=0.004672

  t half= 0.693/k

           = 0.693/0.004672

           =148.33 minutes.

         

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Explanation: