Ch. 15 - SolutionsCh. 15 - Solutions

I. How Solutions Form Definitions Types of Solutions Dissolving Rate of Dissolving

A. DefinitionsA. Definitions

Solution - Solution - homogeneous mixture

Solvent Solvent - present in greater amount

Solute Solute - substance being dissolved

A. DefinitionsA. Definitions

Solute Solute - KMnO4 Solvent Solvent - H2O

B. Types of SolutionsB. Types of Solutions

Based on state of solvent. All solid-liquid-gas combos are

possible. EX: dental amalgam (alloy of silver,

mercury, etc.)• liquid solute, solid solvent• solid solution

C. DissolvingC. Dissolving

SolvationSolvation

• occurs at the surface of the solute

• solvent particles surround solute particles (+/- attraction)

• solute particles are pulled into solution

C. DissolvingC. Dissolving

NaCl dissolving in waterNaCl dissolving in water

D. Rate of SolutionD. Rate of Solution

Solids dissolve faster...Solids dissolve faster...

• more stirring

• small particle size(increased surface area)

• high temperature

D. Rate of SolutionD. Rate of Solution

Gases dissolve faster...Gases dissolve faster...

• no shaking or stirring

• high pressure

• low temperature

A. ConcentrationA. Concentration

Concentrated solutionConcentrated solution • large amount of solute

Dilute solutionDilute solution • small amount of solute

A. ConcentrationA. Concentration

% by Volume% by Volume• usu. liquid in liquid• EX: 10% juice = 10mL juice + 90mL water

% by Mass% by Mass• usu. solid in liquid• EX: 20% NaCl = 20g NaCl + 80g water

A. ConcentrationA. Concentration

SATURATED SOLUTION

no more solute dissolves

UNSATURATED SOLUTIONmore solute dissolves

SUPERSATURATED SOLUTION

becomes unstable, crystals form

concentration

B. SolubilityB. Solubility

SolubilitySolubility• maximum grams of solute that will

dissolve in 100 g of solvent at a given temperature

• varies with temperature• based on a saturated solution

B. SolubilityB. Solubility

Solubility CurveSolubility Curve• shows the

dependence of solubility on temperature

B. SolubilityB. Solubility

Solids are more soluble at...Solids are more soluble at...• high temperatures.

Gases are more soluble at...Gases are more soluble at...• low temperatures.• high pressures

(Henry’s Law).

Ch. 15 - SolutionsCh. 15 - Solutions

III. Particles in Solution “Like Dissolves Like” Electrolytes Colligative Properties

A. “Like Dissolves Like”A. “Like Dissolves Like”

NONPOLAR

NONPOLAR

POLAR

POLAR

DetergentsDetergents• polar “head” with long nonpolar “tail”• can dissolve both types

B. ElectrolytesB. Electrolytes

ElectrolyteNon-

Electrolyte

solute exists asions only

- +

salt

- +

sugar

solute exists asmolecules

only

- +

acetic acid

WeakElectrolyte

solute exists asions and

molecules

B. ElectrolytesB. Electrolytes

DissociationDissociation• separation of +/-

ions when an ionic compound dissolves in water

B. ElectrolytesB. Electrolytes

IonizationIonization• breaking apart of

polar covalent molecules into ions when dissolving in water

C. Colligative PropertiesC. Colligative Properties

properties of solutions that depend only on solute concentration

Freezing Point DepressionFreezing Point Depression• solutes lower the f.p. of a solvent

Boiling Point ElevationBoiling Point Elevation• solutes raise the b.p. of a solvent

C. Colligative PropertiesC. Colligative Properties

View Flash animation.

Freezing Point Depression

C. Colligative PropertiesC. Colligative Properties

Solute particles “get in the way.”

Boiling Point Elevation

C. Colligative PropertiesC. Colligative Properties

Effect increases as the solute concentration increases.

Uses:Uses:• antifreeze• making ice cream• salting icy roads