What is the half life of a radioisotope if you started with 1 gram and 0.250 grams is left after 6 days?

Question

How many days is it going to be?

Answer 1

One of the easiest formulas to use for this type of problem is

FR = 0.5ⁿ

FR = fraction remaining = 0.25

n = # of half lives that have elapsed = ?

0.25 = 0.5ⁿ

log 0.25 = n log 0.5

n = 2

So 2 half lives have elapsed which is equal to 6 days.

t_1/2 = 3 days