Question

Which of the following is a correct graph for molar heat capacity (at constant pressure) versus temperature for an ideal di-atomic gas ?

• A.
• B.
• C.
• D.

Answer 1

The correct option is D

For an ideal gas, molar heat capacity at constant pressure is given by,
$C_p=(\frac{f}{2}+1)R$
For di-atomic gas, degree of freedom $f=5$
$\therefore C_p=(\frac{5}{2}+1)R=\frac{7}{2}R$
$\Rightarrow C_p=\frac{7R}{2}$ and independent of temperature. Hence graph of $C_p\text{Vs}T$ will be a straight line parallel to $T-$axis.