# Homework Help: Question about Ideal Gas Law

1. Jul 3, 2013

### RedemistiDeus

1. The problem statement, all variables and given/known data
A sample containing only NO2 and SO2 has a total pressure of 120 torr. Measurements show that the partial pressure of NO2 is 43 torr. If the vessel has a volume of 800.0 ml and the temperature is 22.0°C, how many moles of each gas are present?

2. Relevant equations

PV = nRT

3. The attempt at a solution
I tried to solve it using the equation above by solving for n for each gas (using their given pressure).
For the n of NO2, I had the answer 3.1 x 10-3 (using n = PV/RT).
But the book provides a different answer for it which is 1.9 x 10-3.

My question is I would like to know how my answer turned to be incorrect. I don't know any other possible methods of solving this than the ideal gas law.
Thank you.

2. Jul 4, 2013

### SteamKing

Staff Emeritus
I suspect you have either an arithmetic mistake and/or a mistake in units.

3. Jul 4, 2013

4. Jul 4, 2013

### RedemistiDeus

Okay guys, I got it. I had an error in manipulating the equations. Thank you PF for helping me resolve the problem!

5. Jul 5, 2013

### Mr. College

I'm curious as to how you arrived at the correct answer. Could you show your work?