Question

In van der Waals' equation of gaseous state, the constant 'b' is a measure of

• A. volume occupied by the molecules
• B. intermolecular repulsions
• C. intermolecular attraction
• D. pressure correction

Hint:

'b' is also known as the excluded volume. For ideal gases, 'b' is zero.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Van der Waals' equation corrects the ideal gas law for the finite size of gas molecules and intermolecular attractions.

Step 2: Detailed Explanation:
The van der Waals' equation for 1 mole of a real gas is: \[ \left(P + \frac{a}{V^2}\right)(V - b) = RT \] • The term 'b' is the volume correction. It accounts for the volume occupied by the gas molecules themselves. It is approximately four times the actual volume of the molecules. • 'a' is the pressure correction term, which accounts for intermolecular attractions.

Step 3: Final Answer:
Constant 'b' is a measure of the volume occupied by the molecules, which corresponds to option (A).