Thermodynamics Question 339
Question: 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 $ 2V _{0} $ . [System is thermally isolated from the surroundings].The heat absorbed by the gas is
Options:
A) $ nRT\ln 2 $
B) $ -nRT\ln 2 $
C) nRT
D) $ -nRT $
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Answer:
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.
