Posted by Hannah on .
1)For the reaction, A = B + C, the rate law is k(A). If it takes 80.0 seconds for 70.0% of a 10.0 gram sample of A to be transformed into products, what is the value of the rate constant?
I was going to do 80/10 = 8 and then 8 times .70 but im not sure this is correct.

Chemistry 
DrBob222,
Haven't I already done this for you? I did for someone.
ln(No/N) = kt
ln(10/3) = k*80
Solve for k.
Note: No = 10; that's the starting amount.
N = amount left. When 70% has been used then 30% is left and 30%*10 = 3.