A glass vessel has a mass of 53.8718 g when evacuated (no air). When filled with a liquid of density 1.319 g mL-1 it has a mass of 255.7390 g and when filled with an unknown gas at 752.3 torr and 16.12°C it has a mass of 54.2483 g. What is the molar mass of the gas, express your answer in scientific notation.?

...i'm confused about the three masses given. from the equation P=d(RT/MM), you don't need mass at all. please help?

3 answers

You don't have the density, do you? The density given is that of a liquid.
how is liquid or the inital mass relevant to the question, if we're only concerned with the gas?
The liquid and mass and density of the liquid gives you a way of determining the volume of the container. Then the volume of the container and the mass of the gas gives you the density of the gas and from that the molar mass of the gas.