The half-life of 198Au is 2.7 days.
(a) Find the activity of a sample containing 1.00 μg of 198Au.
(b) What will be the activity after 7 days? Take the atomic weight of 198Au to 198 g mol-1.
a) 198 g of Au contains 6.023×1023 atoms (Avogadro’s Number)
So 1μg of Au contains atoms
= 3.041 × 1015 atoms
Activity = λN , λ = decay constant =
b) We know,
where A= Activity of the substance
A0 = Initial activity
N = number of half lives
Here