A radioactive sample contains 2.2 mg of pure `._(6)^(11)C` which has a half - life period of 1224 seconds. Calculate the number of atoms present initially, and the activity when `5mug` of the sample will be left.

Explanation

(i) Number of atoms present intially
`=(6.023xx10^(23)xx2.2xx10^(-3))/(11)=1.2xx10^(20)"atoms"`
(ii) No. of atoms present in `5 mu g` of the sample `N=(6.023xx10^(23)xx5xx10^(-6))/(11)=2.74xx10^(17)"atoms"`
Activity of the sample `=lambdaN`
`=(0.693)/(T_(1//2))xxN=(0.693xx2.74xx10^(17))/(1224)=1.55xx10^(14) "disintergration"//"seconds."`