Posted by mary on .
5 mg iodine 131 its half life is 8.1 days what is the time when 1% remain

chemistry 
DrBob222,
k = 0693/t_{1/2}
Solve for k and substitute into the equation below.
ln(No/N) = kt
Use 5mg for No.
Use 1% x 5 = 0.05 for N.
k from above.
Solve for t.
t will be in days if you used 8.1 days for the halflife.