Question

Match the $C _{ P } / C _{ V }$ ratio for ideal gases with different type of molecules :

Molecular type		$C_P /C_V$
A	Monoatomic	I	7/5
B	Diatomic rigid molecules	II	9/7
C	Diatomic non- rigid molecules	III	4/3
D	Triatomic rigid molecules	IV	5/3

• A. A-IV, B-I, C-II, D-III
• B. A-IV, B-II, C-I, D-III
• C. A-III, B-IV, C-II, D-I
• D. A-II, B-III, C-I, D-IV

Answer 1

Answer: (A)

$\gamma=\frac{ C _{ p }}{ C _{ v }}=1+\frac{2}{ f }$
where 'f' is degree of freedom
(A) Monoatomic $f =3, \gamma=1+\frac{2}{3}=\frac{5}{3}$
(B) Diatomic rigid molecules,
$f =5, \gamma=1+\frac{2}{3}=\frac{7}{5}$
(C) Diatomic non-rigid molecules
$f =7, \gamma=1+\frac{2}{7}=\frac{9}{7}$
(D) Triatomic rigid molecules
$f =6, \gamma=1+\frac{2}{6}=\frac{4}{3}$