If half life of iodine 131 is 8 days, how much from 32g remain after 40 days (5 half lives).
1/2^5 = 1/32 of the original amount
To determine how much iodine-131 remains after 40 days (5 half-lives), we need to follow the formula for exponential decay:
Remaining amount = Initial amount * (1/2)^(number of half-lives)
Given that the initial amount is 32 grams and the half-life is 8 days, let's calculate the amount remaining after each half-life:
After the 1st half-life (8 days): Remaining amount = 32 * (1/2)^(1) = 16 grams
After the 2nd half-life (16 days): Remaining amount = 16 * (1/2)^(1) = 8 grams
After the 3rd half-life (24 days): Remaining amount = 8 * (1/2)^(1) = 4 grams
After the 4th half-life (32 days): Remaining amount = 4 * (1/2)^(1) = 2 grams
After the 5th half-life (40 days): Remaining amount = 2 * (1/2)^(1) = 1 gram
Therefore, after 40 days, 1 gram of iodine-131 remains out of the initial 32 grams.