Question

At a constant volume the specific heat of a gas is $0.075$ and its molecular weight is $40$. The gas is :

• A. Monoatomic
• B. Diatomic
• C. Triatomic
• D. None of these

Answer 1

Answer: (A)

We know that,
Molar heat capacity at constant volume,
$C _{ v }=$ Specific heat at constant volume $\times$ Mol. wt.
$=0.075 \times 40=3.0\, cal$
$\because C _{p}- C _{v}= R$
or $C _{p}= R + C _{ v }=2+3=5$
Now, $\frac{ C _{ p }}{ C _{ v }}=\gamma ;$
$\therefore \gamma=\frac{5}{3}=1.66$
This value shows that the gas is monoatomic.