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Solutions of Gases. Solutions of Gases. Many gases are soluble in water. Were it not for the solubility of oxygen, fish would have wear scuba tanks. Besides the characteristics of the gas itself, what are the two external factors which affect the solubility of a gas?. Solutions of Gases.
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Solutions of Gases Many gases are soluble in water. Were it not for the solubility of oxygen, fish would have wear scuba tanks. Besides the characteristics of the gas itself, what are the two external factors which affect the solubility of a gas?
Solutions of Gases Two factors affect the solubility of a gas: The temperature of the solution. The pressure of the gas above the solution. See “Henry’s Law”.
Solutions of Gases The temperature of the solution. Why is the champagne chilled?
Solutions of Gases It tastes better, and the cooler it is the greater the dissolved CO2. As the temperature rises, the dissolved CO2 decreases.
Solutions of Gases The solubility of gases decreases with increasing temperature.
Solutions of Gases Thermal pollution This 1988 thermal image of the Hudson River highlights temperature changes caused by discharge of 2.5 billion gallons of water each day from the Indian Point power plant. The plant sits in the upper right of the photo — hot water in the discharge canal is visible in yellow and red, spreading and cooling across the entire width of the river. Two additional outflows from the Lovett coal-fired power plant are also clearly visible against the natural temperature of the water, in green and blue. http://www.switchstudio.com/waterkeeper/issues/Winter%2007/fight_power_plants.html
Solutions of Gases Thermal pollution The result is a decrease in dissolved oxygen which is needed by the plants and animals living in the heated water.
Solutions of Gases Why do we find trout in cold mountain streams, often near riffles and waterfalls? High dissolved oxygen.
Solutions of Gases The second factor is the pressure of the dissolved gas above the solution. CO2 is dissolved in a can of Pepsi. Above the liquid in the can is CO2 gas. The high pressure of the CO2 in the can keeps the can rigid and the CO2 in solution.
Solutions of Gases Henry’s Law: At a constant temperature, the amount of a given gas dissolved in a solution is directly proportional to the partial pressure of that gas in equilibrium with the solution.
Solutions of Gases p = kHc Henry’s Law: Where p is the partial pressure of the gas, kH is the Henry’s law constant, and c is the concentration of the gas in moles per liter. • Some Henry’s law constants at 298K • O2 769.2 Latm/mol • CO2 29.4 Latm/mol • H2 1282.1 Latm/mol
Solutions of Gases p = kHc Henry’s Law: The pressure of the CO2 in the headspace of can of Pepsi is 4.50 atm at 298K. What is the concentration of the CO2? • Some Henry’s law constants at 298K • O2 769.2 Latm/mol • CO2 29.4 Latm/mol • H2 1282.1 Latm/mol Ans: 0.153 M