Question

Bromine-82 has a half-life of 36 hours. A sample containing Br-82 was found to have an activity of 1.4x10^5 disintegrations/min. How many grams of Br-82 were present in the sample? Assume that there were no other radioactive nuclides in the sample.

Answer 1

Activity rate = decay constant$\lambda$ × Number of mole

$T_{1 \over 2}= 36hours = 129600 secs$

$\therefore \lambda={ln(2) \over 129600} =5.3×10^{-6}$

$N= {A \over \lambda}={2333.3 \over 5.6 × 10^{-6}}= 416660714.28mol$

Mass= mole × molar mass

$416660714.29 × 82 =3.41662×10^{10}gram$