The half-life of tritium or hydrogen-3 is it 12.32 years, after about 24.6 years how much of a sample of tritium remain unchanged?

A 1/3

B 1/2

C 1/8

D 1/4

For the answer to the question above,

The amount of the substance left after sometime, t, is given by the equation,

At = (Ai) x e^-kt

where Ai is the initial amount and k is constant. From the given half-life,

At / Ai = 0.5 = e^-k (12.32); k = 0.5626

Then, for the next set,

At/Ai = e^ (-0.5626) x24.6 = 1/4 So the answer is D.