Suppose a laboratory has a 38 g sample of polonium-210. The half life of polonium-210 is about 138 days.

Question

(A) how many half-lives of polonium-210 occur in 1104 days?

(B) how much polonium-210 is in the sample 1104 days later?

 

A: 9; 0.07 g

 

B: 8; 4.75 g

C: 8; 0.15 g

 

D: 8; 2,622 g

Answer 1

(a)  1104 days/138 day/half life = 8 half lives

 

(b)  fraction remaining = 0.5ⁿ where n is the number of half lives = 8

fraction remaining = 0.5⁸ = 0.003906

38 g x 0.003906 = 0.15 g remain 

 

So, answer would be C: 8; 0.15 g