Gas properties involve four variables: n: amount of gas, in

Last updated: 7/9/2022

Gas properties involve four variables: n: amount of gas, in moles V: volume of gas, in liters P: pressure of gas, in atmospheres T: temperature of gas, in kelvins Although all four of these can change, many times it is convenient to compare gases using a set of "standard" conditions. In particular, we use standard temperature and pressure values and label those standard conditions STP. In the USA, most chemists, and most general chemistry texts, use STP = 0 °C and 1 atm, where the molar volume of any gas is 22.4 L/mol. If the reference pressure is chosen to be 1 bar, the molar volume is 22.7 L/mol. Do not confuse the two. This molar volume can be used as a convenient way of calculating amount (mol) from volume (or volume from amount) for gas samples at STP. 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 = 0°C, 1 atm, where the molar volume = 22.4 L/mol. If the reference pressure is chosen to be 1 bar, the molar volume is 22.7 L/mol. Do not confuse the two. A 0.52 mol sample of hydrogen gas occupies a volume of L at STP.