Tritium, a radioactive isotope of hydrogen, has a half-life of 12.4 years. Of an initial sample of 69 grams, how much will remain after 75 years?
A)0.0000 grams
B)61.5289 grams
C)1.5848 grams
D)17.2500 grams
E)1.0426 grams

Question

Quizplus · Accepted Answer

Using the formula for radioactive decay, we can find the amount remaining:
$N=N_0(1/2)^\frac{t}{T}$
where
$N_0 =$ initial amount
$N =$ amount remaining
$t =$ time passed
$T =$ half-life
Plugging in the given values, we get:
$N = 69(1/2)^\frac{75}{12.4} \approx 1.0426$ grams
Therefore, the answer is E.

Tritium, a Radioactive Isotope of Hydrogen, Has a Half-Life of 12.4