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. A sample of 0.1 g of water at 100°C and normal pressure (1.013 x 105 Nm-2) requires 54 cal of heat energy to convert to steam at 100°C. If the volume of the steam produced is 167.1 cc, the change in internal energy of the sample, is

  • Option 1)

    42.2 J

  • Option 2)

    208.7 J

  • Option 3)

    104.3 J

  • Option 4)

    84.5 J

 

Answers (2)

best_answer

As we have learned

 

First law of Thermodynamics -

Heat imported to a body in is in general used to increase internal energy and work done against external pressure.

- wherein

dQ= dU+dW

 

 

Heat\: Supplied= 54 cal = 54\times 4.2\: J= 226.8\: J

Work\: Done= 54 cal =P\Delta V\: = 1.01\times 10^{5}\times 167.1\times 10^{-6}J

                            = 168.8\times 10^{-\gamma }= 16.88\: J

\therefore \: \: \: \Delta U= 226.8-16.88J\simeq 208.7J

 


Option 1)

42.2 J

This is incorrect

Option 2)

208.7 J

This is correct

Option 3)

104.3 J

This is incorrect

Option 4)

84.5 J

This is incorrect

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Plabita

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