STP (standard temperature and pressure) is used as a reference point for the molar volume of an ideal gas. In the USA, most chemists, most general chemistry texts, and OWL use STP =0C,1atm, where the molar volume =22.4L/mol. If the reference pressure is chosen to be 1 bar, the molar volume is 22.7L/mol. Do not confuse the two. A sample of argon gas collected at STP occupies a volume of 22.4 L. How many moles of gas does the sample contain? mol