Tritium (31h) is an isotope of hydrogen that is sometimes used to make the hands of watches glow in the dark. the half-life of tritium is 12.3 years. after 49 years, approximately how much of the original tritium remains?

6.31%

Explanation:

In order to solve this, you need to use the expression to calculate half life, which is the following:

C = Co e^-t λ  (1)

Where:

C: concentration after t has passed

Co: initial concentration

t: time that has passed

λ: lambda which relation half life time

λ this can be calculated with the following expression:

λ = ln2 / t(1/2)   (2)

So, let's calculate λ first and then, the concentration. In this case, we will assume that we begin with a concentration at 100%.

The value of lambda is:

λ = ln2 / 12.3

λ = 0.0564

Now, let's use (1) to calculate the concentration after 49 years:

C = 100 e^ (-49 * 0.0564)

C = 100 e^(-2.7636)

C = 6.31 %

And this will be the tritium remaining after 49 years