Question

Molar specific heat at constant volume for a non-linear triatomic gas ( neglect vibration of molecules) is:

• A. $3R$
• B. $4R$
• C. $2R$
• D. $R$

Answer 1

The correct option is A $3R$

Molar specific heat at constant volume for a gas is,
$C_v=\frac{fR}{2}$
$f$ is the degree of freedom(D.O.F) of gas.
For a triatomic gas( neglecting vibration):
Translational D.O.F$=3$
Rotational D.O.F$=3$, since gas mlecules will rotate along $x,y,z$ axis respectively.
$\Rightarrow f=3+3=6$
Therefore,
$C_v=\frac{6R}{2}=3R$
$\therefore$Option $\left(a\right)$ is correct.