Which of the following statements are correct?
(i) Temperature changes during the change of a state.
(ii) Dry ice gets converted directly into gaseous state under normal atmospheric conditions.
(iii) Higher boiling points of liquid indicates weaker intermolecular forces.
(iv) Latent heat of vaporization is generally higher than the latent heat of fusion for a substance.
Correct option is :

Question

Accepted Answer

Option 2 is the correct answer, which includes statements (ii) and (iv). Let's explore why these statements are correct and why the other options are incorrect.

1. **Statement (ii): Dry ice gets converted directly into gaseous state under normal atmospheric conditions.**
   - This statement is correct. Dry ice is solid carbon dioxide (CO2), and it sublimates, meaning it changes directly from a solid to a gas without passing through the liquid phase under normal atmospheric pressure. This is a well-known property of dry ice, making statement (ii) accurate.

2. **Statement (iv): Latent heat of vaporization is generally higher than the latent heat of fusion for a substance.**
   - This statement is also correct. The latent heat of vaporization is the amount of energy required to convert a unit mass of a liquid into a gas at constant temperature and pressure. It is generally higher than the latent heat of fusion, which is the energy required to change a unit mass of a solid into a liquid. This is because breaking the intermolecular forces to convert a liquid into a gas requires more energy than converting a solid into a liquid.

Now, let's examine why the other statements are incorrect:

1. **Statement (i): Temperature changes during the change of a state.**
   - This statement is incorrect. During a phase change, such as melting or boiling, the temperature of a substance remains constant until the entire substance has changed its state. The energy added or removed during a phase change is used to alter the state, not to change the temperature.

2. **Statement (iii): Higher boiling points of liquid indicates weaker intermolecular forces.**
   - This statement is incorrect. In fact, higher boiling points indicate stronger intermolecular forces. A liquid with strong intermolecular forces requires more energy (and thus a higher temperature) to overcome these forces and transition into the gaseous state.

By focusing on the correct statements (ii) and (iv), Option 2 is justified as the correct answer.