Question

Molar heat capacity at constant pressure for a non-linear triatomic gas is

• A. $\frac{3R}{2}$
• B. $\frac{5R}{2}$
• C. $4R$
• D. $2R$

Answer 1

The correct option is C $4R$

For a non-linear triatomic gas, it can have degree of freedom as as translational $\left(3\right)$, rotational $\left(2\right)$, vibrational $\left(1\right)$.
$f=3A-B$
For non-linear triatomic, $A=3$ and $B=3$
$\Rightarrow$Total degree of freedom will be, $f=6$
Since,
$C_p=(\frac{f}{2}+1)R$
$\therefore C_p=(\frac{6}{2}+1)R=4R$