Half life of Mn?

Question

The half life of 52/25Mn is 5.6 days. Find out how many half-lives are past after 50.4 days. How much of a 100g sample would be left after that time?

Answer 1

The number of halving times is 50.4/5.6 = 9 halving times. The amount of material left would be 100/2^9 = 0.195 gm.

Answer 2

Well first thing to do is to find out how many half lives in 50.4 days (you are lucky that this result is a whole number) then you just need to raise 1/2 to that whole number power and finally multiply this result by 100 grams and you'll have your answer.

This sounds like a homework Q. so I didn't do the math for you, but the explanation should steer you toward your answer.

Answer 3

Divide 50.4 days by 5.6 days to get the number of half-lives. Then multiply 100 g by 0.5 raised to a power equal to that number of half-lives. For example, if it were instead 56 days, you would find that 10 half-lives have passed, so the amount of Mn remaining would be (100 g)*0.5^10 = 0.0977 g.