Question

A certain element has a half-life of three years.

If you currently have a 10g sample of that element and you know that it has undergone five half-life decays, how many grams of the element were in the sample originally?

A
150g
B
160g
C
320g
D
50g

Answer 1

(C) 320 g

Step-by-step explanation:

A = A02^(-t/hl)

where hl = half-life

A0 = original amount

A = present amount

t = elapsed time = 5 half-lives

10g = A02^(-5) = A0/32

A0 = 32×(10 g) = 320 g