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: .. Vapour Pressure

  1. #1

    Jul 2011
    369

    .. Vapour Pressure

    : Vapor Pressure
    .
    + .

    . .

    Boiling point
    . . /. , .
    . 101,3 . ѡ . . 100 72 3,000 .





  2. #2

    Jul 2011
    369

    : .. Vapour Pressure



    ޡ . . .
    . . . . . ѡ ʡ .
    . . ɡ . . ǡ . ߡ .
    . . ǡ ǡ . . ǡ 100 (-195,8).
    . . 1064,43 2,807. ϡ 1,535 2,750.
    . . 5000 , .
    . . ( latent ) . .
    ( - - ) .
    100
    C 212 F . 260 mbar 69 C .
    99.97 ( 1 101,325 ) . 1982 IUPAC 1 ( 100,000 ) . 99.61 .


  3. #3

    Jul 2011
    369

    : .. Vapour Pressure




    where: TB = the normal boiling point, K R = the ideal gas constant, 8.314 J K-1 mol-1 P0 = is the vapor pressure at a given temperature, atm ΔHvap = the heat of vaporization of the liquid, J/mol T0 = the given temperature, K ln = the natural logarithm to the base e



    A typical vapor pressure chart for various liquids


  4. #4

    Jul 2011
    369

    : .. Vapour Pressure



    Vapor Pressure
    Chemical Concept Demonstrated: Vapor presssure

    Demonstration:

    1. Three universal gas law apparati are needed: one using a 2-L flask, one using a 1-L flask, and one using a 500-mL flask.






    1. 5-10 mL of acetone is injected into the 1-L flask. Determine the pressure.




    1. The same operation is repeated in the 500 mL and 2-L flasks.


    1. Determine the vapor pressure of the acetone as the temperature increases.

    Observations:

    The pressure of the gas inside the three different flasks is the same, given enough time. As the temperature increases, the vapor pressure of the acetone increases.

    Explanations:
    A liquid in a closed container comes to equilibrium (with respect to vapor pressure) when the rate of condensation is equal to the rate of evaporation. Because the rates themselves are independent of surface area, the total vapor pressure in the container is independent of surface area.
    Vapor molecules are molecules that have overcome various intermolecular forces to leave the liquid phase. When heat is applied to the liquid, more molecules gain the energy required to become vapor. This increase in the rate of evaporation shifts the equilibrium of the vapor pressure, causing more molecules to participate in evaporation and condensation. As a result, the vapor press



  5. #5

    Jul 2012
    5,302

    : .. Vapour Pressure


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