A tank contains 25.0 kg of O2 gas at a gauge pressure of 9.10 atm. If the oxygen is replaced by fluorine, how many
kilograms of the latter will be needed to produce a gauge pressure of 4.00 atm?
The Attempt at a Solution
For the O2 we know P, can find n (m=nM), and R is a constant. Still leaves one equation with two unknowns? Am I to assume some temperature, find the volume of the container, and then use that same temperature to calculate the mass of flourine. Is that valid?