At the beginning of the section on gas laws, we said that all gases have the same volume per mole at constant pressure and temperature. We now can calculate what this molar volume is. Scientists refer to 1 atm pressure and
0 (273.15K) as "standard temperature and pressure," or STP. At STP, the volume per mole of a gas is





A 22.4-liter sphere has a diameter of 35 cm, and this was the calculation that produced the figure quoted previously in this chapter. One mole of any gas at STP fills a flask fourteen inches in diameter (right).