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Chapter 6: Solutions

A solution is a homogeneous mixture composed of two or more substances. In such a mixture, a solute is dissolved in another substance, known as a solvent.

Solute SolventAppearance of Solution Example

Gas Liquid Liquid Carbonated waterLiquid Liquid Liquid WineSolid Liquid Liquid Salt water (saline solution)Gas Gas Gas AirSolid Solid Solid 14 Carat gold

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Chapter 6: Characteristics of Solutions

1. The distribution of particles in a solution is 1. The distribution of particles in a solution is uniform.uniform.

2. The components of a solution do not separate 2. The components of a solution do not separate on standing.on standing.

3. A solution cannot be separated into its 3. A solution cannot be separated into its components by filtration.components by filtration.

4. For any given solvent/solute combination, it is 4. For any given solvent/solute combination, it is possible to make solutions of many different possible to make solutions of many different compositions.compositions.

5. Solutions are almost always transparent. Solid 5. Solutions are almost always transparent. Solid solutions are an exception.solutions are an exception.

6. Solutions can be separated into pure 6. Solutions can be separated into pure components. The separation is a physical components. The separation is a physical change, not a chemical change.change, not a chemical change.

Characteristic of SolutionsCharacteristic of Solutions

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Chapter 6: Solubility

SolubilitySolubility: The maximum amount of a solute that dissolves in a : The maximum amount of a solute that dissolves in a given amount of solvent at a given temperature.given amount of solvent at a given temperature.Solubility is a physical property.Solubility is a physical property.

Each solid has a different solubility in every liquid:Each solid has a different solubility in every liquid:Those with low solubility are said to be Those with low solubility are said to be insolubleinsolubleThose with higher solubility are said to be Those with higher solubility are said to be solublesoluble..

Some liquids are insoluble in each other, as for example, gasoline in Some liquids are insoluble in each other, as for example, gasoline in water.water.Other liquids have limited solubility in each other, as for example, Other liquids have limited solubility in each other, as for example, ether in water (6 g/100 g H2O).ether in water (6 g/100 g H2O).Still other liquids are completely soluble in each other, as for Still other liquids are completely soluble in each other, as for example, ethanol and water.example, ethanol and water.

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Chapter 6: Solubility

Saturated solutionSaturated solution: A solution in which the solvent : A solution in which the solvent contains the maximum amount of a solute that can contains the maximum amount of a solute that can be dissolved at equilibrium at a given temperature.be dissolved at equilibrium at a given temperature.

Unsaturated solutionUnsaturated solution: A solution that contains less : A solution that contains less than the maximum amount of a solute that can be than the maximum amount of a solute that can be dissolved at a given temperature.dissolved at a given temperature.

Supersaturated solutionSupersaturated solution: A solution that contains : A solution that contains more than the equilibrium amount of a solute that more than the equilibrium amount of a solute that can be dissolved at a given temperature. When can be dissolved at a given temperature. When this solution is disturbed in any way, the excess this solution is disturbed in any way, the excess solute separates and the equilibrium solubility is solute separates and the equilibrium solubility is restored.restored.

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Chapter 6: Factors Effecting Solubility

Factor Solid or Liquid in a Liquid Gas in a Liquid

Nature of Solvent and

solute

“like dissolves like”Polar is soluble in polarNon-polar in non-polar

No effect

Temperature

Higher T = Higher solubility

With a few exceptions

Higher T = Lower Solubility

With a few exceptions

Pressure No effect

Higher P = Higher solubility

(Henry’s law)

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Chapter 6: Percent Concentration

% w/v = X 100 Mass of solute (g)Volume of solution (mL)

Mass of solute (g)Weight of solution (g)

Volume of solute (mL)Volume of solution (mL)

% w/w = X 100

% v/v = X 100

%

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Chapter 6: Molarity

Molarity (M) = moles of solute (n)liter of solution (L) M

Problem: You need 1L of a 0.1M solution of NaCl. How many moles of NaCl do you need.

How many grams?

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Chapter 6: ppm

ppm = X 1,000,000 Mass of solute (g)Mass of solution (g)

ppm

Problem: 1 L of water contains 2mg of Pb. What is the Pb concentration in ppm?

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Chapter 6: Dilutions

C1 x V1 = C2 x V2

It works with any Concentration or Volume unit, as long as:

• C1 and C2 have the same unit• V1 and V2 have the same unit

Problem: Suppose we have a bottle of concentrated acetic acid (6.0 M). How would you prepare 200mL of a 3.5 M solution of acetic acid ?

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Chapter 6: Water as a solvent

Water is a polar molecule; it is capable of dissolving both

• Ionic compounds

• Covalent Compounds

HCl(g) + H2O(l) Cl-(aq) + H3O+(aq)

Hydronium ion

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Chapter 6: Electrolytes

Ions dissolved in water can migrate from one place to another, maintaining their charge as they migrate.The movement of ions constitutes an electric current.

Electrolyte: A substance that conducts electric current when dissolved in water. A substance that does not conduct electricity is called a nonelectrolyte.Strong electrolyte: A compound that dissociates completely to ions in an aqueous solution.Weak electrolyte: A compound that only partially dissociates to ions in an aqueous solution.

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Chapter 6: Colloids

A colloid is a type of mixture in which one substance is dispersed evenly throughout another.A colloidal system consists of two separate phases: a dispersed phase (or internal phase) and a continuous phase (or dispersion medium). A colloidal system may be solid, liquid, or gaseous.

Type of Colloid Example

Gas in gasGas in liquidGas in solidLiquid in gasLiquid in liquidLiquid in solidSolid in gasSolid in liquidSolid in solid

NoneWhipped creamMarshmallowsClouds, fogMilk, mayonnaiseCheese, butterSmokeJellyDried paint

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Chapter 6: Colligative Properties

Colligative property: Any property of a solution that depends on the number of solute particles, and not on the nature of the particles.

Important colligative properties:

• Freezing-point depression• Boiling-point elevation• Osmotic pressure

Osmolarity = M x i

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Chapter 6: Osmosis

Isotonic solutions: Solutions with the same osmolarity.

Hypotonic solution: a solution with lower osmolarity than blood plasma and red blood cells.

Hypertonic solution: a solution with higher osmolarity than red blood cells.

Hemolysis: The swelling and bursting of red blood cells because they cannot resist the increase in osmotic pressure when put into a hypotonic solution.