One mole of an ideal gas occupies a volume of _________ litre at 273 K and 1 atm pressure.

22.4

The correct answer is option 4. 22.4.

The volume occupied by one mole of an ideal gas at standard temperature and pressure (STP) conditions is known as the molar volume. At STP, the conditions are defined as a temperature of 273.15 K (0 degrees Celsius) and a pressure of 1 atmosphere (atm).

The molar volume of an ideal gas at STP is approximately \(22.4 \, \text{litres/mol}\). This value is a result of the ideal gas law equation \(PV = nRT\), where:

- \(P\) is the pressure (in pascals),
- \(V\) is the volume (in cubic meters),
- \(n\) is the number of moles,
- \(R\) is the ideal gas constant, and
- \(T\) is the temperature (in kelvins).

At STP, when \(P = 1 \, \text{atm}\), \(T = 273.15 \, \text{K}\), and \(n = 1 \, \text{mol}\), the molar volume (\(V\)) is \(22.4 \, \text{litres/mol}\). This relationship is useful for calculations involving the volume of gases under standard conditions.