Question

I've figured out most of it. I'm not sure how to find the percentage ofd the isotope.
Define the half life. The half-life of a radioisotope is found to be 4.55 minutes. If the decay follows first order kinetics, what percentage of isotope will remain after 2.00 hours if you start with 10.00 g?
T1/2= (.693)/k 4.55min = (.693)/k k =.152min-1

Answer 1

Never mind I figured it out
Ln(At)=-(.152min-1)(120min)+ln(10)
Ln(At)= -18.24+(2.30)
Ln(At)=-15.9
e^At=e^-15.9
At= 1.19 x 10^-7
%=1.19 x 10^-7 x 100
=1.19 x 10^-5 % of the isotope