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Question
A gas contained in a cylinder fitted with a frictionless piston expands against a constant pressure 1 atmosphere from a volume of 4 litre to a volume of 14 litre. In doing so, it absorbs 800 J thermal energy from surrounding . Determine △U for the process.
A gas contained in a cylinder fitted with a frictionless piston expands against a constant pressure 1 atmosphere from a volume of 4 litre to a volume of 14 litre. In doing so, it absorbs 800 J thermal energy from surrounding . Determine △U for the process.
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Solution
The correct option is A −213.25 J
Given,
Heat absorbed, q=800 J
Again, the gas expands from 4 L to 14 L
∴△V=(14−4)=10 litre
We know, work done by the gas, w=PΔV
w=−1×10=−10 litre - atm
Again,
1L−atm=101.325 J
∴−10 L−atm=−1013.25 J
According to the first law of thermodynamics,
ΔU=q+w
△U=q+w=(800−1013.25)=−213.25 J
Given,
Heat absorbed, q=800 J
Again, the gas expands from 4 L to 14 L
∴△V=(14−4)=10 litre
We know, work done by the gas, w=PΔV
w=−1×10=−10 litre - atm
Again,
1L−atm=101.325 J
∴−10 L−atm=−1013.25 J
According to the first law of thermodynamics,
ΔU=q+w
△U=q+w=(800−1013.25)=−213.25 J
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