# Homework Help: I don't understand this Vapor Concept problem?

1. Oct 11, 2012

### Mackydoodle

1. The problem statement, all variables and given/known data

If oxygen gas occupies 25mL at -25 'C and 65 mm Hg.
What is the volume at 25 'C and 350 mmHg?

2. Relevant equations

P1+P2+P3=Ptotal

3. The attempt at a solution
I am really not sure how to do this :(
I think maybe I figured it out. Please see below!

Last edited: Oct 11, 2012
2. Oct 11, 2012

### bigfooted

I don't understand P1+P2+P3=Ptotal.

The volume of a gas changes, depending on pressure and temperature. Do you know a law that describes this? (It is a law that describes an ideal gas)

3. Oct 11, 2012

### Mackydoodle

The ideal gas law equation

Ok I think I might have the answer this is what I cam up with but Im not sure.....
Here it is:

25mL/248K = X/298K

Which equals 30.04mL (I still don't believe this is right)

Last edited: Oct 11, 2012
4. Oct 11, 2012

### Staff: Mentor

It has nothing to do with the ideal gas equation. If anything, it looks like Dalton's law.

Correct approach, but you need to hone your calculator skills.