The half-life of Au-198 is 2.7 days.After 10.8 days of decay only 1.30 g of a sample remains.What was the mass of the original sample?

Question

Quizplus · Accepted Answer

After 10.8 days, which is 4 half-lives (10.8 days / 2.7 days per half-life = 4 half-lives), the mass of the sample would have halved 4 times. Starting with 1.30 g and doubling it 4 times (because we are going backwards in time) gives us 1.30 g * 2^4 = 1.30 g * 16 = 20.8 g.

The Half-Life of Au-198 Is 2