Tritium, a radioactive isotope of hydrogen, has a half-life of 12.4 years. Of an initial sample of 79 grams, how much will remain after 6 years?
A)0.0725 grams
B)62.5417 grams
C)56.4895 grams
D)18.8581 grams
E)19.7500 grams

Question

Quizplus · Accepted Answer

Using the formula for radioactive decay:
N = N0 * (1/2)^(t/t1/2)
where N is the final amount, N0 is the initial amount, t is the time elapsed, and t1/2 is the half-life.

Plugging in the values: 
N = 79 * (1/2)^(6/12.4) 
N = 56.4895 grams

Therefore, the amount of Tritium remaining after 6 years is 56.4895 grams. The answer is choice C.

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