If the half life of Ir - 131 is 42 days, how much would be remaining after 168 days?
isn't that four half lives?
amountremaining=origamount*(1/2)^4
or
amount=orig *e^(-.693*168/42)
To calculate the amount remaining after a certain number of half-lives, you can use the formula:
Amount remaining = Initial amount * (1/2)^(number of half-lives)
In this case, the half-life of Ir-131 is 42 days, and you want to know how much would be remaining after 168 days, which is 4 times the half-life.
So, let's calculate the number of half-lives:
Number of half-lives = Time elapsed / Half-life
= 168 days / 42 days
= 4
Now, substitute the values into the formula:
Amount remaining = Initial amount * (1/2)^(number of half-lives)
Since the initial amount is not given, we cannot calculate the exact quantity remaining. We can only calculate the fraction remaining.
Amount remaining = (1/2)^(4)
= 1/16
So, after 168 days, approximately 1/16th of the initial amount of Ir-131 will remain.