chemistry
posted by anonymous .
The decomposition of N2O5 proceeds according to the following equation
2 N2O5(g) → 4 NO2(g) + O2(g).
The rate constant, k, for the reaction at 298 K is 2.20 x 103 min1. If a reaction is set up in a vessel at 298 K, with an initial concentration of 0.343 mol L1; what is the concentration of reactant N2O5(g) in mol/L after 42 minutes?

The units of min^1 tell you that the reaction is first order.
So ln(No/N) = kt.
No is starting.
N is end
k from problem
t = 42 min 
298/0.343 = 868
868/42 = 21.000 
Nope. You didn't substitute. And you know the answer can't be right. You start with 0.343 mol, it decomposes and you have more than you started with after 43 mn. I don't think so.