Question

Half life of krypton is 3.16 minutes.out of 100g of krypton.how much will be left after 9.48 minutes?

Answer 1

12.5g of Krypton will be left

In 9.48 min it will complete three half lives.

Answer 2

radioactivity is taken as first order reaction....

and half life of first order rxn

T½= 0.693/K

so

K = 5.714

now by the eqn kf first order rxn

K = (2.303 log100/x)/ T

I am sorry this is a complicated method.. let me try with another method

N/ No = (1/2)^ (t/ t½)

N/100 = (1/2)^ ( 9.48/ 3.16)

N/100 =( 1/2)^ 3

N/100 = 1/8

N = 100/8

N = 12.5 gm... rhis is answer.