Question

For a gas, \(\frac{R}{C_v} = 0.4\) where R is the universal gas constant and \(C_v\) is the molar specific heat at constant volume. The gas is made up of molecules which are

• A. monoatomic
• B. polyatomic
• C. non rigid diatomic
• D. rigid diatomic

Hint:

R/Cv = 0.4 gives Cv = 5R/2, which is a rigid diatomic gas.

Answer 1

The Correct Option is D

Step 1: Use gamma:
$\gamma-1=\dfrac{R}{C_v}=0.4$, so $\gamma=1.4=\dfrac75$.

Step 2: Match gamma:
$\gamma=1.67$ for monatomic and $\gamma=1.4$ for rigid diatomic. A non-rigid diatomic gas has $\gamma=1.29$.

Step 3: Pick:
Rigid diatomic, option D.

Final Answer:
R/Cv = 0.4 gives Cv = 5R/2, so f = 5 and the gas is rigid diatomic. \[ \boxed{\text{(D) }\text{rigid diatomic}} \]