Avogadro and Gasses

(pre: Avogadro's Number)

Avogadro's Law (Avogadro-Ampère Hypothesis)

Law

Equal volumes of all gasses at the same temperature and pressure, have the same number of molecules.

Molar Volume

Definition

The molar volume of a gas is the space occupied by one mole of that gas:

where:

  • is the universal gas constant

(see Measuring a Gas)

Note: , not the same as molarity, which is .

At STP, we have

Example

At and , of oxygen occupy a volume of . What is the molar volume of oxygen gas at this temperature and pressure?

solution
Note