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Homework Help: Solubility of a gas in water Kinetic Molecular Theory

  1. Jun 26, 2008 #1
    1. The problem statement, all variables and given/known data

    The solubility of a gas in water decreases as temperature
    increases, and increases as temperature decreases. Using
    the kinetic molecular theory, explain why this is so.

    I would like an opinion please on my answer below. Is it a sufficient explanation?
    THANKS!!! :smile:

    3. The attempt at a solution

    According to the Kinetic Molecular Theory, when you increase temperature, the
    gas moleclues are moving faster causing the solubility to decrease because of
    more collision between the particles. When the temperature decreases, the gas
    molecules are not moving as fast, causing them to have a higher solubility.
  2. jcsd
  3. Jun 26, 2008 #2
    How about this:

    According to the kinetic molecular theory, increasing the temperature of water increases the kinetic energy of gas (and water) molecules, which then causes them to move faster. I learned in Physics that this is how evaporation works: Fast moving water molecules collide with other molecules near the surface. The molecules near the surface may then possess enough kinetic energy to break free from the water. Now going back to the problem, when water is heated, gas molecules are given more energy causing them to move faster, which causes more molecules to leave the liquid. Thus, the solubility of a gas in water decreases because gas molecules will tend to be bumped out of the water. However, when the temperature is decreased, the kinetic energy of the molecules is decreased, creating lower-speed collisions. It is then easier for gas molecules to stay dissolved in the water.

    **this is actually a Chemistry problem.**
  4. Jun 27, 2008 #3
    My side:

    Increased temperature causes an increase in kinetic energy. The higher kinetic energy causes more motion in molecules which break intermolecular bonds and escape from solution.

    This gas solubility relationship can be remembered if you think about what happens to a "soda pop" as it stands around for awhile at room temperature. The taste is very "flat" since more of the "tangy" carbon dioxide bubbles have escaped. Boiled water also tastes "flat" because all of the oxygen gas has been removed by heating.
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