Question

For an ideal gas, the heat capacity at constant pressure is larger than that at constant volume because

• A. positive work is done during expansion of the gas by the external pressure
• B. positive work is done during expansion by the gas against external pressure
• C. positive work is done during expansion by the gas against intermolecular forces of attraction
• D. more collisions occur per unit time when volume is kept constant

Answer 1

The correct option is B positive work is done during expansion by the gas against external pressure

When heat is supplied at constant volume, temperature increases accordingly to the ideal gas equation.

$P=\frac{nRT}{V}$

as V is constant and T is increasing, pressure will also increase.

Than at constant pressure as temperature is increase volume increases, resulting in expansion of the gas, resulting in positive work, Hence the heat given is used up for expansion and then to increases the internal energy . The heat capacity at constant pressure is larger.