Calculating Number Density of Gas Molecules

1. The problem statement, all variables and given/known data
What is the number density, N/V, of gas molecules in the closed vessel in the previous problem?

(Previous problem: A closed vessel contains an ideal gas at an absolute pressure of 1.5 atm and a termperature of 42 degrees celsius. To what final temperature (in °C) must the gas be heated so its final pressure is 2.0 atm?

2. Relevant equations

pV=N$k\ =\ 1.3806503(24)\ \times\ 10^{-23}\ J\ K^{-1}$T

3. The attempt at a solution
From the previous problem I have p=2.0 atm, T=420K and reorganizing the equation I get N/V=p/$k\ =\ 1.3806503(24)\ \times\ 10^{-23}\ J\ K^{-1}$T

so N/V=2.0atm/$k\ =\ 1.3806503(24)\ \times\ 10^{-23}\ J\ K^{-1}$(420K) = 3.45×10^20. The answer is supposed to be 3.5×10^25. I cannot figure out why I am getting the wrong answer, can anybody shed some light on this?

http://ift.tt/1q18dju