¹³¹I has a half life of 8 days. Approximately how long will it take a sample with an activity of 60 mCi to drop to about 3.75 mCi?

Question

Quizplus · Accepted Answer

The half-life of ¹³¹I is 8 days, which means that every 8 days, the activity will be reduced by half. To find the number of half-lives required to reduce the activity from 60 mCi to 3.75 mCi, we can use the formula: N = (log(N0/N))/log(2) where N0 is the initial activity (60 mCi), N is the final activity (3.75 mCi), and log is the logarithm to the base 2. Plugging in the values, we get: N = (log(60/3.75))/log(2) = 4.89 This means that it will take approximately 4.89 half-lives to reduce the activity from 60 mCi to 3.75 mCi. Since the half-life is 8 days, it will take approximately 8 x 4.89 = 39.12 days to reach the final activity of 3.75 mCi. Rounded to the nearest whole number, this gives us 39 days. Therefore, the best choice is C: 32 days.

131I Has a Half Life of 8 Days

¹³¹I Has a Half Life of 8 Days