Ideal Gas Equation

NH₃​ (g) will show maximum deviation from ideal gas due to dipole-dipole attraction.

The derivation of an ideal gas is dependent upon the Van der Waals constant for which hydrogen bonding, liquefiable process, and intermolecular forces of attraction are taken into consideration.

• NH₃(g), among the four given gases, is easily liquefiable, i.e., it has the strongest intermolecular forces of attraction.
• This is the reason why its Van der Waals constant value is also high.

Therefore, the maximum deviation from ideal gas is expected from NH₃(g) due to dipole-dipole attraction leading to more attractive forces between molecules of NH₃.

Alternate Approach - 1

The explanation for the correct answer - Option (i) NH₃ (g)

The deviation from ideal gas depends on temperature and pressure. NH₃ is the most easily liquefiable gas out of all the options provided above. Since it has strong intermolecular forces so the van der wall constant is high, so it exhibits maximum deviation. Hence, option (i) is correct.

The explanation for incorrect answer:

• Option (ii) H₃ - In H₃ there is no Hydrogen bonding and it has weak intermolecular forces. So, it does not exhibit maximum deviation. So, option (B) is incorrect.
• Option (iii) N₂ - In N₂ the intermolecular forces between the molecule are weak and are not easily liquifiable. Hence, option (C) is incorrect.
• Option (iv) CH₄ - There is no H bonding in CH₄, so the intermolecular forces of attraction are also weak. Hence, the Van der Waals constants a & b are lesser for this molecule.

Alternate Approach - 2

The extent to which a real gas deviates from its ideal behaviour is determined by a quantity 'Z' known as the compressibility factor. Easily liquefiable gases like NH₃, SO₂​ etc. exhibit maximum deviation from ideal gas as for them Z<<<1. CH₄​ also exhibits deviation but it is less as compared to NH₃.

Alternate Approach - 3

Hint: Maximum deviation from ideal gas is related to the Van der Waals constant. One fact is that no real gas shows deviation from an ideal gas. We can consider the various facts like hydrogen bonding, intermolecular forces of attraction and liquefiable process. Ammonia (NH₃) is a highly liquefiable gas.

Complete step by step answer:

Van Der Waals constant a & b shows the dependence on the ideal behaviour shown by gas.

• If we talk about the H₃ (g), N₂ (g), and CH₂ (g), there is no H bonding in these molecules, and intermolecular forces of attraction are also weak. So, the Van der Waals constants a & b are less for these molecules.
• The last three gases are not easily liquefied, but if we say about NH₃ (g), it is easily liquefiable gas among these four gases.
• NH₃ (g) is a polar molecule as it has the presence of hydrogen bonding.
• In NH₃ (g), there are strong intermolecular forces of attraction, so the van der Waals constant value is high.
• Therefore, the maximum deviation from the ideal gas is expected from NH₃ (g). Thus, the correct option is (i).

Note: Don’t find the values of the Van der Waals constant. Remember the points about real gases and ideal gas behaviour shown by the multiple gas molecules.

To find the total pressure of the gas mixture, we need to use the ideal gas law given by:

, where:

• is the pressure in atm.
• is the volume in liters.
• is the number of moles.
• is the ideal gas constant, given as .
• is the temperature in Kelvin, given as .

First, we calculate the number of moles for each gas using their respective molecular weights:

• Molecular weight of
• Moles of
• Molecular weight of
• Moles of

Total moles in the mixture = .

Substituting into the ideal gas equation for total pressure:

.

Thus, the correct option is .