Question

Iodine-131 is a radioactive isotope. If $1.0mg$ of ${}^{131}I$ has an activity of $4.6\times {10}^{12}Bq$. What is the half-life of ${}^{131}I$ (in days)?

Answer 1

As we know, activity is $A=\lambda N$

$3.6\times {10}^{12}\times 3.7\times {10}^{10}=\frac{0.693}{t_{1/2}}\times \frac{{10}^{-3}}{131}\times 6.023\times {10}^{23}$

So $t_{1/2}=8$