posted by Rachel .
A 150.0 mL flask contains 0.391 grams of a volatile oxide of sulfur. The pressure in the flask is 750 mmHg and the temperature is 22C. Is the gas SO2 or SO3?
Use PV = nRT and solve for n.
Then n = grams/molar mass.
Solve for molar mass.
Compare with molar mass SO2 and SO3.