Question

Tritium is a radioactive isotope of hydrogen which emits beta particles and decays to form helium-3 as time passes. Its half-life is 12.3 years; that is, after 12.3 years, half of the tritium in a sample will have decayed to helium-3. An initial quantity of 180 milligrams of tritium decays for y years. Which expression gives in milligrams the remaining quantity of tritium in the sample after y years?

Answer 1

`N=(180)* e^{(y)/(12.3)}` mg

Step-by-step explanation:

For radioactive decay of an radioactive isotope-

`N=N_(0)e^{(\frac{t}{t_{(1)/(2)}})}`

Where N is amount of radioactive isotope after "t" time,
`N_(0)` is initial amount of radioactive isotope and
`t_{(1)/(2)}` is half-life of radioactive isotope

Here,
`N_(0)` = 180 mg,
`t_{(1)/(2)}` = 12.3 years, t = y years

So,
`N=(180)* e^{(y)/(12.3)}` mg

The above expression gives the remaining quantity of tritium after y years