Kinetic Theory Ques 19
19. One mole of an ideal diatomic gas undergoes a transition from $A$ to $B$ along a path $AB$ as shown in the figure.The change in internal energy of the gas during the transition is:
[2015]
(a) $-20 $ $kJ$
(b) $20 $ $J$
(c) $-12$ $ kJ$
(d) $20$ $ kJ$
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Answer:
Correct Answer: 19.(a)
Solution:
- (a) Change in internal energy from $A \to B$
$\Delta U=\frac{f}{2} nR \Delta T=\frac{f}{2} nR(T_f-T_i)$
$=\frac{5}{2}\{P_f V_f-P_i V_i\}$
$=\frac{5}{2}\{2 \times 10^{3} \times 6-5 \times 10^{3} \times 4\}$
$=\frac{5}{2}\{12-20\} \times 10^{3} J=5 \times(-4) \times 10^{3} $ $ J$
$\Delta U=-20 $ $KJ$
(As gas is diatomic $\therefore f=5$ )
BETA
