| Direction: An ideal diatomic gas is confined in a cylinder A of volume \[{{V}_{0}},\] this cylinder is connected to another cylinder B with the help of tube of a negligible volume. The cylinder B is fitted with a movable piston which can be adjusted from outside. Initially, the piston is adjusted so that volume of B is the same as volume of A i.e., \[{{V}_{0}}\]. B is evacuated and the stopcork is opened so that gas expands and occupies the volume \[2{{V}_{0}}\]. [System is thermally isolated from the surroundings]. |
 |
| The heat absorbed by the gas is |
A) \[nRT\text{ }\ln \text{ }2\]
B) \[-nRT\text{ }\ln \text{ }2\]
C) nRT
D) \[-nRT\]
Correct Answer: B
Solution :
| [b] From 1st law of thermodynamics, |
| \[dQ=dU+dW\] |
| \[\Rightarrow \,dU=0\] for constant temperature process |
| \[\Rightarrow \,dQ=dW\] |
| \[\Rightarrow \,dQ=-nRT\,\,\ln \,\,2\] |
| Negative sign shows that heat is released by the system. |
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