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JEE MainPhysicsThermodynamics

0.1 kg of a liquid at its boiling point is completely converted into vapour at a constant pressure of 10^5 Pa . The latent heat of vaporization of the liquid is 5 10^5 J/kg and the expansion in volume during this phase change is 0.05 m ^3 . The percentage of the total heat supplied that is used to increase the internal energy of the system is :

Options

  1. A10 %
  2. B110 %
  3. C90 %
  4. D100 %

Correct answer

C. 90 %

Step-by-step solution

Total heat supplied to the liquid for vaporization is: Q = m L Q = 0.1 (5 10^5) = 50000 J Work done by the system during expansion at constant pressure is: W = P V W = 10^5 0.05 = 5000 J According to the first law of thermodynamics: Q = U + W U = 50000 - 5000 = 45000 J The percentage of the total heat supplied that is used to increase the internal energy is: Percentage = ( U Q ) 100 Percentage = ( 45000 50000 ) 100 = 90 % Answer: 90 %

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