Question

The half-life of a radioactive isotope is 10 years. About how long would it take 5 grams of the isotope to decay until there were only 2.5 grams left?
A. 10 years
B. 20 years
C. 30 years
D. 40 years

Answer 1

Answer:

Option A. 10 years

Step-by-step explanation:

we know that

Half-life $(t^{\frac{1}{2}})$ is the amount of time required for a quantity to fall to half its value as measured at the beginning of the time period.

In this problem  $(t^{\frac{1}{2}})$ of a radioactive isotope is 10 years, which means that after 10 years half of the sample would have decayed and half would be left as it is.

After 10 years ( first half life) 5/2 = 2.5 g decays and 2.5 g remains left