Kinetic Theory Of Gases Question 99

Question: One mole of a diatomic gas is taken through the process $ PV^{n}=k, $ where n and k are constant. If the heat capacity of gas is negative, then the value of n may be

Options:

A) $ \frac{5}{7} $

B) $ -\frac{5}{7} $

C) $ \frac{9}{7} $

D) $ -\frac{9}{7} $

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Answer:

Correct Answer: C

Solution:

[c] $ C=\frac{R}{\gamma -1}+\frac{R}{1-n} $ for a polytropic process
$ \Rightarrow C=\frac{5R}{2}+\frac{R}{1-n}\text{ }( \

Therefore r=\frac{7}{5}\text{ for a doatomic gas} ) $ For C to be negative, the possible value of 9 n will be $ \frac{9}{7}. $