Half-life of a radioisotope of tritium,or hydrogen-3, is 12.32 years. After 37 years, how much of will remain?

Question

The half-life of a radioisotope of tritium, or hydrogen-3, is 12.32 years. After about 37 years, how much of a sample of tritium will be left?

1 - one-eighth
2 - one-fourth
3 - one-third
4 - one-half

Answer 1

correct answer is (1)- i.e- one-eighth

Answer 2

1 - one-eighth


Half-life of a radioisotope of tritium,or hydrogen-3, is 12.32 years.

Thus t½ = 12.32 years

Time period of 37 years is about 3 times the t½
(because 12.32*3=~37)

After 2 times t½ ,it decays to 1/4th

After 3 times t½ ,it decays to 1/8th

OR

you can use the general formula 1/2ⁿ, where "n" is the number of half lives!

Answer 3

After the first half-life (12.32 years) half of the original sample will remain. After another half-life (24.64 years in all) half of the remaining will disappear. In other words only one-fourth is left. After the third half-life (36.96 years in all, since the beginning) half of that one-fourth (or one-eighth of the original sample) remains. So, the answer is 1/8.

Answer 4

After 1 half-life (12.32 yrs) 1/2 of the original amount remains.
After 2 half-lives (24.64 yrs) 1/4 of the original amount remains.
After 3 half-lives (36.96 yrs) 1/8 of the original amount remains.