Question

A gas is cooled and loses 50 J of heat. The gas contracts as it cools and work done on the system equal to 20 J is exchanged with the surroundings. Hence, ∆E is :
a) 70 J b) -30 J c) 30 J d) -70 J

Answer 1

Answer:

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Explanation:

According to first law of thermodynamics △E=Q+W

Q=−50 J ( loses heat )

W=+20 J ( work is done on the gas )  

Hence △E=−50+20

△E=−30J

Hence, option B is correct.

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Answer 2

Answer:

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