# Homework Help: Ideal Gas - Oxygen in a tank

1. Sep 30, 2009

### tweety24

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

A welder fills a tank, volume 7.60 x 10^-2 m^3, with oxgyen (32.0 g/mol) at gauge pressure 3.25 x 10^5 Pa and temp. 36.0 degrees C. The tank has a small leak, and some of the oxygen leaks. When temp. is 22.4 degrees C, pressure of oxygen in tank is 1.80 x 10^5 Pa.

Find initial mass of oxygen.
Find mass of oxygen that leaked out.

2. Relevant equations

pV = nRT

3. The attempt at a solution

I understand that I need to find the answer to the first part in order to get the answer to the second part. I used the ideal gas law equation to solve the first part and got the answer to be 308 grams but it keeps telling me thats wrong.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Sep 30, 2009

### rock.freak667

Try converting the gauge pressure to absolute pressure by adding the atmospheric pressure to the gauge pressure.

3. Sep 30, 2009

### tweety24

thanks I tried that and got the correct answer :)