The molar heat capacity of oxygen gas at `STP` is nearly `2.5 R`. As the temperature is increased, it gradually increase and approaches `3.5 R`. The most appropriate reason for this behaviour is that at high temperatures

Options

A. oxygen does not behave as an ideal gas
B. oxygen molecules dissociated into atoms
C. the molecules collide more frequently
D. molecular vibrations gradually become effective

Answer

D

Explanation

The molar heat capacity depends upon the degree of freedom. At low temperature only translatory degree of freedom is present. At high temperature all types of degrees of freedom (translatory, rotatory and vibratory) are present.