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Vapor Pressure of Gas/Liquid

  • Page ID
    131429
  • In this demonstration the reddish brown color of the Br2 vapor in a sealed vessel intensifies as the vessel is heated

    Required Training

    Required PPE

    UC Lab Safety Fundamentals

    Lab coat, safety glasses/goggles, nitrile gloves

    Equipment

    Chemicals

    Seal tubes w/ Br

    Water

    Hot Plate

    Ice bath (ice, water and NaCl)

    Two 500ml beakers or two 1000ml beakers

    Procedure:

    1. Prepare a warm water bath by heating 300ml water to 50oC in 500ml beaker. Do not place tubes in water bath if temp is greater than 58oC.
    2. Prepare ice-water bath 250ml ice in 500ml beaker and add 50ml water.
    3. Place a bromine tube in the ice water bath and the bromine vapors will condense.
    4. Place a bromine tube in the warm water bath and the bromine vapors will expand and be most intense.

    Discussion:

    Bromine is a reddish brown, volatile, diatomic liquid with a suffocating odor. Its melting point is -7.25oC and its normal boiling point is 59.47oC. Bromine is suitable for demonstrating the effects of temperature on the vapor pressure of a liquid. The intensity of a deep reddish brown color of the vapor is a direct indication of the vapor pressure.

    Hazards:

    The boiling point of bromine is 59oC, and the vapor pressure of bromine is over 1 atm above this temperature. Therefore the tubes should not be immersed in baths above this temperature, to avoid creating high pressures within the tubes.

    SOP: clipboard_e247960766f22671dca24d8de91f89f33.png

    Corrosive – Barium Hydroxide, Sulfuric Acid

    Disposal (by Storeroom)

    Slowly pour a concentrated sodium thiosulfate (Na2S2O3) solution into the cylinder until the bromine has been reduced. Caution! Exothermic reaction, the mixture will become hot. Flush the resulting cooled solution down the drain with water.

    Acknoledgement and adapted from:

    B. Z. Shakhashiri Chemical Demonstrations; A Handbook for Teachers of Chemistry Vol.2, Wisconsin, 1989, Vol.2, p.75-77

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