1. The problem statement, all variables and given/known data A welder using a tank of volume 8.00×10−2 m^3 fills it with oxygen (with a molar mass of 32.0 g/mol ) at a gauge pressure of 3.10×105 Pa and temperature of 38.9 ∘C. The tank has a small leak, and in time some of the oxygen leaks out. On a day when the temperature is 23.0 ∘C, the gauge pressure of the oxygen in the tank is 1.75×105 Pa . Find the initial mass of oxygen. 2. Relevant equations pV=nRT where p is pressure, v is volume, n is number of mole, R is 8.31442(since p is Pa and V is in m^3), and T is kelvin. m total = n*M ; where n is number of moles and M is molar mass. 3. The attempt at a solution pV = nRT = 3.10 * 10^5 * 8.00 * 10^(-2) = n*8.314472* 312.05 n = 9.558 9.558 * 0.032 kg/mol = 0.305856 however, 0.305856 is incorrect. where did i make mistake?