Calculate volumes of gases given masses of some substances in reactions, and calculate masses of substances given gaseous volumes, in reactions involving gases at 0˚C and 100kPa or 25˚C and 100kPa
Avogadro’s hypothesis was that equal volumes of gases contain the same number of molecules (at the same temperature and pressure).
Rearranged, this provides that equal numbers of molecules of different gases occupy the same volume (at the same temperature and pressure).
Since a mole is a number of molecules, a mole of any gas has the same volume of a mole of any other mass.
At 0°C and 100 kPa, the molar volume of all gases is 22.71 L.
At 25°C and 100 kPa, the molar volume of all gases is 24.79 L.
For example, to determine the volume of hydrogen produced at 0°C an 100 kPa when 2.5 g of sodium reacts with excess water, the following calculations can be performed:
To determine mass from volume, the above calculations can be performed in reverse.