Solutions of Gases

Solutions of Solutions of GasesGases

Solutions of GasesSolutions of GasesMany gases are soluble in water. Were Many gases are soluble in water. Were it not for the solubility of oxygen, fish it not for the solubility of oxygen, fish would have wear scuba tanks.would have wear scuba tanks.

Besides the characteristics Besides the characteristics of the gas itself, what are of the gas itself, what are the two external factors the two external factors which affect the solubility which affect the solubility of a gas?of a gas?

Solutions of GasesSolutions of Gases

The temperature of the solution.The temperature of the solution.

The pressure of the gas above the The pressure of the gas above the solution. See “Henry’s Law”. solution. See “Henry’s Law”.

Two factors affect the solubility Two factors affect the solubility of a gas:of a gas:


The temperature of the solution.The temperature of the solution.

Why is the Why is the champagne champagne

chilled?chilled?

Solutions of GasesSolutions of GasesIt tastes better, It tastes better, and the cooler it and the cooler it is the greater the is the greater the dissolved COdissolved CO22..

As the As the temperature rises, temperature rises, the dissolved COthe dissolved CO22

decreases.decreases.


The solubility of The solubility of gases decreases gases decreases with increasing with increasing temperature.temperature.

http://www.switchstudio.com/waterkeeper/issues/Winter%2007/fight_power_plants.htmlhttp://www.switchstudio.com/waterkeeper/issues/Winter%2007/fight_power_plants.html

Thermal pollutionThermal pollutionThis 1988 thermal image of the Hudson This 1988 thermal image of the Hudson River highlights temperature changes caused River highlights temperature changes caused by discharge of 2.5 billion gallons of water by discharge of 2.5 billion gallons of water each day from the Indian Point power plant. each day from the Indian Point power plant. The plant sits in the upper right of the photo The plant sits in the upper right of the photo — hot water in the discharge canal is visible — hot water in the discharge canal is visible in yellow and red, spreading and cooling in yellow and red, spreading and cooling across the entire width of the river. Two across the entire width of the river. Two additional outflows from the Lovett coal-additional outflows from the Lovett coal-fired power plant are also clearly visible fired power plant are also clearly visible against the natural temperature of the water, against the natural temperature of the water, in green and blue. in green and blue.


Thermal pollutionThermal pollution

The result is a decrease in The result is a decrease in dissolved oxygen which is dissolved oxygen which is needed by the plants and needed by the plants and animals living in the animals living in the heated water.heated water.


Solutions of GasesSolutions of GasesWhy do we find trout in cold Why do we find trout in cold mountain streams, often near riffles mountain streams, often near riffles and waterfalls?and waterfalls?

High dissolved oxygen.High dissolved oxygen.


COCO22 is dissolved in a can of is dissolved in a can of

Pepsi. Above the liquid in Pepsi. Above the liquid in the can is COthe can is CO22 gas. The high gas. The high

pressure of the COpressure of the CO22 in the in the

can keeps the can rigid and can keeps the can rigid and the COthe CO22 in solution. in solution.

The second factor is the pressure of the The second factor is the pressure of the dissolved gas above the solution.dissolved gas above the solution.

Solutions of GasesSolutions of GasesHenry’s Law:Henry’s Law:At a constant temperature, At a constant temperature, the amount of a given gas the amount of a given gas dissolved in a solution is dissolved in a solution is directly proportional to the directly proportional to the partial pressure of that gas partial pressure of that gas in equilibrium with the in equilibrium with the solution.solution.

Solutions of GasesSolutions of GasesHenry’s Law:Henry’s Law: p = kp = kHHcc

Where Where pp is the partial pressure of is the partial pressure of the gas, the gas, kkHH is the Henry’s law is the Henry’s law

constant, and constant, and cc is the concentration is the concentration of the gas in moles per liter.of the gas in moles per liter.

Some Henry’s law constants at 298KSome Henry’s law constants at 298KOO22 769.2 Latm/mol769.2 Latm/mol

COCO22 29.4 Latm/mol29.4 Latm/mol

HH22 1282.1 Latm/mol1282.1 Latm/mol

Solutions of GasesSolutions of GasesHenry’s Law:Henry’s Law: p = kp = kHHcc

The pressure of the COThe pressure of the CO22 in the in the

headspace of can of Pepsi is headspace of can of Pepsi is 4.50 atm at 298K. What is the 4.50 atm at 298K. What is the concentration of the COconcentration of the CO22??

Some Henry’s law constants at 298KSome Henry’s law constants at 298KOO22 769.2 Latm/mol769.2 Latm/mol

COCO22 29.4 Latm/mol29.4 Latm/mol

HH22 1282.1 Latm/mol1282.1 Latm/mol0.153 M0.153 MAns:Ans:

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Solutions of Gases