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99 Percentile Qs Bank for JEE MainChemistryThermodynamics (C)

A gas absorbs 200 ~J heat and expands by 500 ~cm ^3 against a constant external pressure 2 10^5 ~N ~m ⁻² . What is the change in internal energy?

Options

  1. A800 ~J
  2. B-750 ~J
  3. C100 ~J
  4. D-150 ~J

Correct answer

C. 100 ~J

Step-by-step solution

aligned & V=500 ~cm ^3=0.5 dm ^3 & P _ ext =2 10^5 ~N ~m ⁻²=2 bar & (since, 1 10^5 ~N ~m ⁻²=1 bar) & W =- P _ ext V & =-2 (0.5) & =-1 dm ^3 bar & W =-100 ~J ( since, 1 dm ^3 bar =100 ~J ) & According to first law of thermodynamics, & U=Q+W=200 ~J -100 ~J =+100 ~J & aligned

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