Question

1g of a radioactive substance disintegrates at the rate of `3.7xx10^(10)` disintegrations per second. The atomic massof the substance is 226. Calculate its mean life.

Answer 1

We known , number of nuclei present ,`N=(m)/(M)N_(A)`
where , m=given mass ,M= atomic mass
`N_(A) `= Avogadro number
Activity , `R=lamda N =(1)/(tau)(mN_(A))/(M)`
where , `tau` = mean life .
Maean life of substance , `tau =(mN_(A))/(MR)=(1xx6.023xx10^(23))/(226xx3.7xx10^(10))s`
`=7.2xx10^(10)s`