The half-life of 92U238 against alpha decay is 4.5 x 109 years. How many disintegrations per second occur in 1 g of 92U238 ?
Suggested solution:
Again, since one k mole of any isotope contains Avogadro's number of atoms, there fore 1 g of 92U238 contains
Half life T = 4.5 109 years
Again, since one k mole of any isotope contains Avogadro's number of atoms, therefore 1g of 92U238 contains,
= 4.20 x 10-6k mole x 6.025 x 1026 atoms / k mole
= 25.3 x 1020 atoms
Decay rate,
= 1.23 x 104 s-1
