Question

The latent heat of vaporization of a substance is always:

• A. Greater than its latent heat of fusions
• B. Greater than its latent heat of sublimation
• C. Equal to its latent heat of sublimation
• D. Less than its latent heat of fusion

Answer 1

The correct option is A

Greater than its latent heat of fusions

Explanation for correct answer:

In case of option A,

1. The latent heat of vaporization can be defined as the heat energy released when $1kg$ of liquid changes to $1kg$ of gas.
2. The latent heat of fusion can be defined as the heat energy released when $1kg$ of solid changes to $1kg$ of liquid.
3. To change from liquid to gas, a lot of heat energy is required to break the intermolecular forces between the liquid molecules to change it into gas, which is greater than the heat energy required to just weaken the intermolecular forces between the solid molecules to change it into liquid.

Explanation for incorrect answers:

In case of option B,

1. The latent heat of sublimation can be defined as the heat energy released when $1kg$ of solid changes directly to $1kg$ of gas, without any change in temperature.
2. The latent heat in this process is negligible, a lot lesser as compared to the latent heat of vaporization.
3. Thus, this option is incorrect.

In case of option C,

1. The latent heat of sublimation can be defined as the heat energy released when $1kg$ of solid changes directly to $1kg$ of gas, without any change in temperature.
2. The latent heat in this process is negligible, a lot lesser and therefore not equal compared to the latent heat of vaporization.
3. Thus, this option is incorrect.

In case of option D,

1. The latent heat of fusion can be defined as the heat energy released when $1kg$ of solid changes to $1kg$ of liquid.
2. To change from liquid to gas, a lot of heat energy is required to break the intermolecular forces between the liquid molecules to change it into gas, which is greater than the heat energy required to just weaken the intermolecular forces between the solid molecules to change it into liquid.
3. Thus, this option is incorrect.

Hence, option A is correct.