Posted by Adrianna on .
The halflife of the first order reaction, A to products, is 53.2 s. What was the original concentration, (A)0 in moles per liter, if after 1.8 minutes, the concentration of A is 0.0783 moles per liter?
Not sure whether to use integrated rate law or half life law?

Chemistry 
DrBob222,
k = 0.693/t_{1/2}
Substitute into the expression below for k.
ln(No/N) = kt.
No = unknown
N = 0.0783
t = time. You must change this t to seconds if you use the half life in seconds or you can change the half life in seconds to minutes in which case you make use t in the lower equation in minutes. 
Chemistry 
Adrianna,
Thank you!