Chemistry
posted by m .
I've figured out most of it. I'm not sure how to find the percentage ofd the isotope.
Define the half life. The halflife 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 =.152min1

Chemistry 
m
Never mind I figured it out
Ln(At)=(.152min1)(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
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