### Neet Solved Paper 2015 Question 21

##### Question: 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

#### Options:

A) 20 kJ

B) -20 kJ

C) 20 J

D) -12 kJ

## Show Answer

#### Answer:

Correct Answer: B

#### Solution:

For a diatomic gas, $ C _{V}=\frac{5}{2}R $

The change in internal energy of gas in the transition from A to B is $ \Delta U=nC _{v}dT $

$ =n( \frac{5R}{2} )(T _{B}-T _{A}) $

$ =nR\frac{5}{2}( \frac{p _{B}V _{B}}{nR}\frac{p _{A}V _{A}}{nR} ) $

$ =\frac{5}{2}(2\times 10^{3}\times 6-5\times 10^{3}\times 4) $

$ =\frac{5}{2}\times (-8\times 10^{3}) $ $ =-\frac{4\times 10^{4}}{2}=-20KJ $