Question

An isotope has a half-life of 8 hours. What percentage of the isotope will be left after 24 hours?

a) 12.5%
b) 25%
c) 37.5%
d) 50%

Answer 1

After 24 hours, which is equivalent to three half-lives of the isotope with an 8-hour half-life, only 12.5% of the isotope will remain.

Step-by-step explanation:

The isotope in question has a half-life of 8 hours. To determine what percentage of the isotope will be left after 24 hours, we must calculate the amount of isotope remaining after three half-lives (since 24 hours is three times 8 hours).

• After the first 8 hours (one half-life), 50% of the isotope will remain.
• After 16 hours (two half-lives), 25% of the original amount will remain (50% of 50%).
• After 24 hours (three half-lives), 12.5% of the original amount will remain (50% of 25%).

Therefore, the answer to the question is a) 12.5% of the isotope will be left after 24 hours.