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






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