Question

Consider the following statements I. Repulsive forces are significant when the molecules are close together on average. II. Attractive intermolecular forces are important when the molecules are fairly close together but not necessarily touching. III. Attractive forces are ineffective when the molecules are for apart. Select correct statements.

• A. I, II and III
• B. I and III
• C. II and III
• D. I and II

Answer 1

The Correct Option is A

The question asks us to evaluate three statements regarding intermolecular forces. Let's analyze each statement step-by-step:

1. Statement I: "Repulsive forces are significant when the molecules are close together on average."
   • Explanation: Repulsive forces between molecules become significant when the molecules are in close proximity. This is because when molecules are very close, their electron clouds overlap, leading to a force that pushes the molecules apart. Thus, this statement is correct.
2. Statement II: "Attractive intermolecular forces are important when the molecules are fairly close together but not necessarily touching."
   • Explanation: Attractive forces, such as van der Waals forces or hydrogen bonding, are significant when molecules are near each other but not necessarily in contact. These forces decrease rapidly with distance yet play a crucial role in the behavior of molecules at moderate distances. Hence, this statement is also correct.
3. Statement III: "Attractive forces are ineffective when the molecules are far apart."
   • Explanation: As the distance between molecules increases, attractive forces diminish rapidly and become negligible. This is consistent with the nature of these forces, which are very weak at large separations. Therefore, this statement is correct.

After analyzing each statement, we can conclude that all three statements are correct. Therefore, the correct answer is:

• I, II and III