Posted by Alex on .
The following rearrangement reaction is first order:
C3H6 ¨ CH3CH=CH2
The rate constant for this reaction is 6.7 ~ 10−4. How many minutes will it take for the concentration of C3H6 to drop to 11.75% of its initial value?
How do I calculate this step by step.
My answer was 3.1 minutes and it was wrong.

Chemistry 
DrBob222,
You don't have any units on k. Also, I'm not sure I've translated the mumbo jumbo symbols you have correctly so check the below carefully.
ln(No/N) = kt
No = 100
N = 11.75
k = 6.7E4 (min^1 or sec^1 or whatever)
t = time and the time will be minutes, seconds, hours, days, or whatever the unit of k. Then time will need to be convert to minutes if k is in some unit other than minutes.