Molar Volume Formula, Definition and Example - Testbook.com

The molar volume, denoted as , refers to the volume that one mole of a substance occupies at Standard Temperature and Pressure (STP). It's an essential concept in chemistry, providing insights into the properties of different elements and compounds. The molar volume is a function of the molar mass and the mass density of the substance. For gases, the molar volume is constant at a specific temperature and pressure.

The molar volume of a substance is calculated by dividing its molar mass by its density. The formula is expressed as:

In this equation, represents the molar volume of the substance.

The standard temperature used in these calculations is 273 Kelvin or 0°C, and the standard pressure is 1 atmosphere, which is equivalent to 760 mm Hg.

As a rule of thumb, one mole of any gas at STP occupies a volume of 22.4 litres. This can be written as:

1 mole of gas at STP = 22.4 litres of gas.

Example:

Let's calculate the molar volume for a sample of Oxygen (O₂) if the density of the gas is 1.429 g/L.

Solution:

We use the formula:

The molar mass of Oxygen = 32 g/mol

= (32)/(1.429)

= 22.39 L