how many half lives will it take for 50 g of 99Tc to decay to 6.25 g?

Answer 1

Let n = number of half lives.

50/6.25 = 8
2^n = 8
n = ?

Answer 2

46

Answer 3

As-81 started as 100 g solution and was reduced by two half-lives.

Answer 4

As-81 started as 100 g solution and was reduced by two half-lives.