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Homework Help: Specific heat capacity of gases

  1. Apr 23, 2015 #1
    1. The problem statement, all variables and given/known data

    Figure shows two rigid vessels A and B, each of volume 200 cm3 containing an ideal gas (Cv = 12.5 J/mol-K). The vessels are connected to a manometer tube
    containing mercury. The pressure in both the vessels is 75 cm of mercury and the temperature is 300 . (b) 5.0 J
    of heat is supplied to the gas in the vessel A and 10 J to the gas in the vessel B. Assuming no appreciable transfer of heat from A to B calculate the difference in the heights of mercury in the two sides of the manometer

    2. Relevant equations


    3. The attempt at a solution

    I know that when we give heat to both vessel, the pressure will increase. So the mercury column will also move and there will be a difference in the height in two arms . But my book says when we give heat to vessl there of gas in both vessel will be same. So according to my book ΔW=0 for both vessel. But since mercury will move, one gas should expand and other should compress. Please help me .
  2. jcsd
  3. Apr 23, 2015 #2
    They are assuming that the volume available for expansion and contraction of the gases within the manometer tube is negligible.

  4. Apr 23, 2015 #3
    OK thanks . But they should mention it .
  5. Apr 23, 2015 #4
    Yes, they should, since the figure seems to suggest that there is volume available for gas expansion and contraction in the manometer tube. But it obviously is not drawn to scale.

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