Number of Mole and Volume of Gas

Molar Volume of Gas

  1. Equal amount of gas occupies same volume of space.
  2. Molar volume of a gas is defined as the volume occupied by one mol the gas at certain condition
  3. At room temperature(25ºC) and pressure (1 atm), one mole of any gas occupies a volume of 24 dm³ (24 000 cm³ )
  4. At standard temperature(0ºC) and pressure (1 atm) one mole of any gas occupies a volume of 22.4 dm³ (22400cm³).

Number of mole of gasses Volume at s.t.p. (dm3)
1 mol of O2 gas  1 x 22.4 = 22.4
1 mol of H2 gas  1 x 22.4 = 22.4
2 mol of He gas  2 x 22.4 = 44.8
3.5 mol of N2 gas  3.5 x 22.4 = 78.4

Number of mole of gasses Volume at r.t.p. (dm3)
1 mol of O2  gas  1 x 24 = 24
1 mol of H2 gas  1 x 24 = 24
2 mol of He gas  2 x 24 = 48
3.5 mol of N2 gas  3.5 x 24 = 84

Example:
What volume (at room temperature and pressure r.t.p.) would 2 moles of oxygen gas occupy? (Molar Gas Volume at r.t.p. = 24 dm³)

Answer:
Volume of gas = 2 x 24 = 48 dm³


Example:
A sample of ozone gas has a volume of 960cm³ at room temperature and pressure. Find the number of mole of the ozone. [Molar volume at r.t.p. = 24.0dm³]

Answer:
Number of mole = 960 cm 3 24000 cm 3 =0.04 mol