Question

Select the correct statement –

• A. When attractive forces are dominant in a real gas U internal energy increases by increasing the average molecular separation
• B. Isothermal contraction decreases the internal energy when repulsive forces between molecules exist
• C. For an ideal gas at constant T internal energy is function of volume only.
• D. In case of attractive forces between particle, if the volume of the sample expands isothermally its dU< 0

Answer 1

Answer: (A)

When attractive forces are dominant in a real gas U internal energy increases by increasing the average molecular separation

Answer 2

Constant temperature,

® For a perfect gas U is independent of volume.

® In case of attraction (real gases) U increases with volume as molecules on an average go apart

® If repulsions are dominant the internal energy decreases with isothermal expansion of the gas.