Question

Suppose a laboratory has a 38 g sample of polonium-210. The half-life of polonium-210 is about 138 days. How many half-lives of polonium-210 occur in 1104 days? How much polonium is in the sample 1104 days later

Answer 1

Since the half life occurs every 138 days, this means that the amount of polonium will be halved every time a half life occurs (eg - first half life would be in 138 days and 38/2 or 19 grams would remain).

Therefore, we divide the given number of days by the half life:
1104/138 = 8 half llives

At 8 half lives, the sample has been divided in half 8 times (compounded)
Therefore we need to multiply the original sample amount by (1/2)^8 or 0.00390625
39 * 0.00390625 = about 0.1523 grams.

Answer 2

perfect explanation! thanks!