Question

A real gas obeying van der Waals equations will resemble ideal gas, if the

• A. Constants a and b both are small
• B. A is large and b is small
• C. A is small and b is large
• D. Constants a and b both are large.

Answer 1

Answer: (A)

Constants a and b both are small

Answer 2

: According to van der Waals equation for 1 mole of a real gas, $\left( P + \frac{a}{V^{2}} \right)(v - b) = RT$

If a and b are small, $a/v^{2}$and b can be neglected as compared to p and V and the equation reduces to PV = RT. Hence, a real gas will resemble an ideal gas when constants a and b are small