Mass of an unknown gas of 50 mL volume at 25 degrees C. and 740 mm of Hg pressure was 0.056 g. The molecular mass of this gas is...

1 answer

PV = nRT and solve for n = mol gas.
Then n = grams/molar mass
Solve for molar mass.
Don't forget T must be in kelvin and P: must be in atm. 740 mm = 740/760 atm