Phase changes: Problems

1. The latent heat of vaporization of water at 100oC is 539 kcal/kg. Calculate the boiling point of water at  600 mm Hg. The value of the universal gas constant is  1.98 cal/mole oK.

solution


2. The vapor pressure of a substance is 723 mm Hg at 10oC and 769 mm Hg  at 11.2oC. Calculate the latent heat of vaporizzation of the substance.

solution


3. 10 g of nitrogen (Mw = 28) are bubbled into liquid bromine (Mw = 160) at 720 mm Hg and 35 oC. Assuming that

Calculate the grams of bromine vaporized.


4. Calculate the fusion temperature for sulphur (atomic weight = 32) at 1000 atm. It is known that at 1 atm:

  • fusion temperature  = 387oC

  • change in volume during fusion = 0.041 l/kg

  • latent heat of fusion = 0.420 kcal/mole

  • Furthermore, assume that the difference between the volume of the solid and that of the liquid is constant, i.e., is the same at any considered pressure.


    5. Calculate the volume and the enthalpy content of a steam at 120oC and 80% quality.


    6. How much heat will evolve when steam (100% quality) at 125 oC and 232.1 kPa is cooled to 120 oC at the same pressure ?


    7. Water at 25 oC is added to a completely evacuated vessel (0 atm). Calculate the pressure in the vessel when the equilibrium liquid vapor is reached a 25 oC.


    8. Water at 25 oC is added to vessel containing dry air at 1 atm. Assuming that no air escaped the vessel after the addition of water, calculate the pressure in the vessel when the equilibrium liquid vapor is reached a 25 oC.