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15.2

• The dissolving medium is the solvent. This is usually present in the greater amount!

• The particles that are being dissolved is called the solute. The solute is usually present in the lesser amount!

Solvent + Solute = Solution

• If you filter a solution through filter paper, both the solute and the solvent pass through the filter.

• A solution cannot be separated by Filtration!

15.2

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Non-PolarNon-Polar

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Turn in your homework from the weekend

Homework 1-14-13Read Section 8.3

1.Create Outline

2.Complete Questions #1-6

• The process by which a solute dissolves in a solvent is called the Solution Process.

• For Ionic Solids, the solution process is a three step process:

1. Solvent particles “surround” the ionic solute particles.

2. Solvent particles pull ionic compounds into solution.

3. Solvent & solute particles spread apart to form a homogenous mixture.

• In the first step, water molecules cluster around the solute aligning their polar ends with that of the solute.

• In Step 1 of the Solution Process, the positive & negative ions of an ionic solid become surrounded by solvent molecules

• This step is called solvation.

• In Step 2 of the solution process, the solvent ions pulls individual solute ions away from the solid crystal.

• In Step 3 of the solution process, individual solute ions break away from the crystal.

• The negatively & positively charged ions become surrounded by solvent molecules, and the ionic crystal dissolves to form a homogenous mixture.

15.2

• A solvent dissolves the solute. The solute becomes dispersed in the solvent.– Solvents and solutes may be gases, liquids or

solids.

– Solute particles can be atoms, ions or molecules.

15.2

“Likes dissolve Likes”“Likes dissolve Likes”

• Polar solvents such as water dissolve ionic & polar solutes such as salt & sugar.

• Non-polar solvents such as gasoline dissolve non-polar solutes such as wax.

“Likes dissolve Likes”“Likes dissolve Likes”

Non-polar liquids like vegetable oil do not mix with polar solvents like water and vinegar

Solubility: Is the maximum amount of solute that can be dissolved in a solvent at a given temp

The Amount of Solubility is dependent on: The solute The solvent The temperature

LikeDissolves

Like

SolubilityCurve

SATURATED SOLUTION: Is a solution that has the maximum amount of solute dissolved in a solvent at a given temperature.

UNSATURATED SOLUTION: Is a solution that can dissolve more solute at a given temperature.

SUPER SATURATED SOLUTION: Is a solution that has more solute than a saturated solution at a given temperature.

This occurs when a saturated solution is cooled with no “energy source” to precipitate the solute from solution

Saturated

Unsaturated

Supersaturated

• Any point below the solubility curve represents an unsaturated solution.

• In an unsaturated solution, the solvent contains less than the maximum amount of solute.

• Example– At 90oC, 30 g of NaCl(s) in

100g H2O(l) represent an unsaturated solution. 10 g of NaCl(s) have to be added to make the solution saturated.

This graph shows theamounts of afew solutesthat can dissolve in 100g of H2Oat various temperatures

Each point on eachcurve is a solution’ssaturation at that temperature.

For example, howmuch potassiumnitrate will forma saturated solutionin 100g of H2Oat 50 degrees C?

What happens ifThis solution isCooled to 40 degrees C?

In a saturated solution, the number of solute ions going into solution, are equal to the number of solute ions coming out of solution (crystallizing).

• Any point on the Solubility Curve line represents a saturated solution.

• In a saturated solution, the solvent contains the maximum amount of solute.

• Example– At 90oC, 40 g of NaCl(s) in

100g H2O(l) represent a saturated solution.

• Any point above the solubility curve represents an supersaturated solution.

• In a supersaturated solution, the solvent contains more than the maximum amount of solute.

• A supersaturated solution is very unstable and the amount in excess can precipitate or crystallize.

• Example– At 90oC, 50 g of NaCl(s) in 100g H2O(l)

represent a supersaturated solution. Eventually, 10 g of NaCl(s) will precipitate.

Any solution can be made saturated, unsaturated, or supersaturated by changing the temperature.

Solubilities of Solids vs TemperatureSolubilities of several ionic solids as a function of temperature. MOST salts have greater solubility in hot water.

A few salts have negative heat of solution, (exothermic process) and they become less soluble with increasing temperature.

“Solubility Curve” or Temperature effects on solubilityThis graph shows theamounts of afew solutesthat can dissolve in 100g of H2Oat various temperatures

Each point on eachcurve is a solution’ssaturation at that temperature.

For example, howmuch potassiumnitrate will forma saturated solutionin 100g of H2Oat 50 degrees C?

What happens ifThis solution isCooled to 40 degrees C?

• The solubility of solutes is dependent on temperature.

• When a solid dissolves in a liquid, a change in the physical state of the solid analogous to melting takes place.

• Heat is required to break the bonds holding the molecules in the solid solute together.

• The use of first-aid instant cold packs is an application of this solubility principle.

• A salt such as ammonium nitrate is dissolved in water after a sharp blow breaks the containers for each.

• The dissolving reaction is endothermic - requires heat. Therefore the heat is drawn from the surroundings, the pack feels cold.

Decrease in solubility with temperature

• With some solids, the heat given off by solvation is greater than the heat required to break apart the solid, the net dissolving reaction is exothermic (energy given off).

• The addition of more heat slows the dissolving reaction since excess heat is already being produced by the reaction.

• This situation is not very common where an increase in temperature produces a decrease in solubility.

• The use of first-aid instant Hot Packs is an application of this solubility principle.

• A salt such as Calcium Chloride or Magnesium Sulfate is dissolved in water after a sharp blow breaks the containers for each.

• The dissolving reaction is exothermic – gives off heat. Therefore the heat is given off to its surroundings, the pack feels hot..

• The solubility of gases in a liquid are the opposite of solids in a liquid.

• The solubility of a gas in a liquid decreases as the temperature increases.

What environmental effect can this have with the operation of Nuclear Power Plants?

Henry’s Law: There is a direct relationship between the solubility of a gas in a liquid and the pressure of the gas:

– As the pressure increases the solubility of a gas in a liquid increases.

S1 S2

P1 P2

=

Henry’s Law:

Henry’s Law & Soft Drinks• Soft drinks contain “carbonated

water” – water with dissolved carbon dioxide gas.

• The drinks are bottled with a CO2 pressure greater than 1atm.

• When the bottle is opened, the pressure of CO2 decreases and the solubility of CO2 also decreases, according to Henry’s Law.

• Therefore, bubbles of CO2 escape from solution.

• Carbonated beverages provide the best example of this phenomena. All carbonated beverages are bottled under pressure to increase the carbon dioxide dissolved in solution.

• When the bottle is opened, the pressure above the solution decreases. As a result, the solution effervesces and some of the carbon dioxide bubbles off.

• Question: Champagne continues to ferment in the bottle. The fermentation produces CO2. Why is the cork wired on a bottle of champagne?

• Answer: As more CO2 is formed, the pressure of the gas increase.The wire is to prevent the cork from blowing off.

• Deep sea divers may experience a condition called the "bends" if they do not readjust slowly to the lower pressure at the surface.

• As a result of breathing compressed air and being subjected to high pressures caused by water depth, the amount of nitrogen dissolved in blood and other tissues increases.

• If the diver returns to the surface too rapidly, the nitrogen forms bubbles in the blood as it becomes less soluble due to a decrease in pressure. The nitrogen bubbles can cause great pain and possibly death.

• To alleviate this problem, artificial breathing mixtures of oxygen and helium are used. Helium is only one-fifth as soluble in blood as nitrogen. As a result, there is less dissolved gas to form bubbles.

• Question: If a diver had the "bends", describe how this can be treated.

• Answer: Decompression chambers are used to keep a high pressure and gradually lower the pressure.

• Another application of Henry's Law is in the administration of anesthetic gases. If the partial pressure of the anesthetic gas is increased, the anesthetic solubility increases in the blood.

Factors Affecting Solubility1. 1. Nature of Solute / SolventNature of Solute / Solvent. - Like dissolves like

2. 2. Temperature -Temperature -i) Solids/Liquids- Solubility increases with Temperature

- Increase K.E. increases motion and collision between solute / solvent.

ii) Gas - Solubility decreases with Temperature- Increase K.E. result in gas escaping to atmosphere.

3. 3. Pressure Factor -Pressure Factor -i) Solids/Liquids - Very little effect

- Solids and Liquids are already close together, extra pressure will not increase solubility.

ii) Gas - Solubility increases with Pressure.- Increase pressure squeezes gas solute into solvent.

The Cleansing Action of Soap

Soap has both polar and non-polar properties

How does soap work?How does soap work?

What is concentration?

• Percent by Volume

Volume of Solute X 100

Volume of solution

• Percent by Mass

Mass of Solute X 100

Mass of solution