Chemistry Kinetics
posted by Tasneem .
2. At 600 K the decomposition of gas ohase nitroethane (CH3CH2NO2) is first order with a rate constant of 1.9*10^4 s^1.
CH3CH2NO2 > C2H4 + HNO2
a) Write out the differential and integrated rate laws for this reaction.
b) If a 10.0g sample of nitroethane is heated to 600K, what mass of nitroethane would be decomposed after 2.8 hours?

I assume you can do a from your text or notes. Look it up if you have doubts.
b.
ln(No/N) = kt
No = 10.0g
N = unknown
k = 1.9E4 sec^1 (but this must be converted to hours or the time below into seconds).
t = 2.8 hours.
Solve for N to find how much remains, then subtract from 10.0 to find the amount decomposed. 
Worked! Thank you!  Why is it ln(No/N) = kt though? The formula I have in my notes for first order reactions is ln(N1/No) = kt

BECAUSE THE MINUS SIGN WAS REMOVED IN THE EQUATION