# Homework Help: Partial pressure and moles problem?

1. Jan 9, 2012

### gh_pluvilias

1. The problem statement, all variables and given/known data
Here is the problem: Carbon monoxide and oxygen are kept at exactly 300 K in separate chambers of the apparatus shown below. When the stopcock is opened, the combustion reaction begins and is allowed to proceed to completion, while being maintained at exactly 300 K.

2. Relevant equations
PV=nRT
I believe the balanced equation is: 2CO + O2 → 2CO2

3. The attempt at a solution
I have 3 questions to answer regarding it. I have typed up what I think are the answer or what I have so far. If you can help me answer these it would be greatly appreciated.

1. How many moles of each reactant are present before the reaction begins?
2 moles of CO2 react with 1 mole of O2 in this reaction.

2. How many moles of each gaseous reactant and product are present when the reaction goes to completion? Assume the connecting tube has negligible volume.
After the reaction is complete, 2 moles of CO2 remain (equal amount of starting CO).

3. What is the partial pressure of each gas when the reaction goes to completion? Assume the connecting tube has negligible volume.
CO2:O2 ratio = 2:1 For NO, 0.5*2/(0.082*300) = 0.041 mol of NO
For O2, 1*1/(0.082*300) = 0.041 mol of O2, 0.02 corrected for ratio.
O2 is the limiting reagent (there won't be any left), so pressure due to O2=0, mass of O2=0.
Not sure what to do from here. =/

2. Jan 9, 2012

### Staff: Mentor

The answer is not related to the question. And the data you have listed so far is not enough to answer the question, could be there was additional data on the image.

Where did you got nitrogen from? You started with CO and O2 only.

3. Jan 9, 2012

### gh_pluvilias

Oh sorry... it was late. Must've have just typed NO instead of CO. lol Guess I get my oxides mixed up.

There is an image attached, but I thought I had included it in my attempts. Sorry. There's 1L of O2 at 1atm and 2L of CO at 0.5atm. And that is all the information I'm given.