Kinetic Theory Ques 18
18. A gas mixture consists of $2$ moles of $O_2$ and $4$ moles of $Ar$ at temperature $T$. Neglecting all vibrational modes, the total internal energy of the system is :-
[2017]
(a) $15 $ $RT$
(b) $9 $ $RT$
(c) $11 $ $RT$
(d) $4 $ $RT$
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Answer:
Correct Answer: 18.(c)
Solution:
- (c) Internal energy of the system is given by
$U=\frac{f}{2} $ $nRT$
Degree of freedom
$F _{\text{diatomic }}=5$
$f _{\text{monoatomic }}=3$
and, number of moles
$n(O_2)=2$
$n(Ar)=4$
$U _{\text{total }}=\frac{5}{2}(2) RT+\frac{3}{2}(4) RT=11$ $ RT$
BETA
