Question

2. The half life of uranium-232 is 68.9 years. a) If you have a 100 gram sample, how much would be left after 250 years? b) If you have a 100 gram sample, how long would it take for there to be 12.5 grams remaining?

Answer 1

Step-by-step explanation:

The amount left is:

A = A₀ (½)^(t/T)

where A₀ is the initial amount,

t is the amount of time,

and T is the half life.

a) A = 100 g (½)^(250 yr / 68.9 yr)

A = 8.09 g

b) 12.5 g = 100 g (½)^(t / 68.9 yr)

0.125 = (½)^(t / 68.9 yr)

3 = t / 68.9 yr

t = 206.7 yr