Question

If 100 g of Au-198 decays to 6.25 g in 10.8 days, what is the half-life of Au-198?

Answer 1

Half life of 2.7 days

Explanation:

Since Au-198 is 100 g originally and it decays to 6.25 g,

You'd divide 100 g by 2 until you reach 6.25 g:

`100/2 = 50`; `50/2 = 25`; `25/2 = 12.5`; `12.5/2 = 6.25`

Since there were four 2s, divide 10.8 days by 4:

`"10.8 days"/4 = "2.7 days"`

100 g of Au-198 would have a half life of 2.7 days.