Electrolytes

ElectrolytesIonic compounds

Break down into positive and negative ions

Conduct electricity

Essential to us !!!

Strong vs. Weak Electrolytes

Weak—electrolytes partially breaking down in a solution

Strong—electrolytes completely breaking down in a solution

NonelectrolytesMolecular compounds

Break down into molecules

Do NOT conduct electricity

Colligative Properties

What are colligative properties?

Physical properties

Based on # of solute particles, NOT identity!!!

4 properties1) Vapor Pressure Lowering

2) Freezing Point Depression

3) Boiling Point Elevation

4) Osmotic Pressure

1) Vapor Pressure Lowering

Nonvolatile vs. volatile chemicals Nonvolatile

Not likely to be a gasTakes awhile for gas particles to evaporate

Volatile Gas particles evaporate quickly

Vapor PressurePressure exerted from gas molecules on a liquidCharacteristic of a liquid

Volatile vs. Nonvolatile Liquids

1) Volatile LiquidsWEAK intermolecular forcesHigh vapor pressureEx. Gasoline, alcohols, “Whoosh Bottle”

2) Nonvolatile Liquids STRONG intermolecular forces Low vapor pressure

More Vapor Pressure….

INCREASED vapor pressurePure solvent Particles can easily move between the liquid and

gas phase to create an equal amount of particles in each phase (equilibrium)

DECREASED vapor pressure Solvent + soluteNumber of particles in the solution is increasedLess water/solvent can evaporate

2) Freezing Point Depression

“difference between freezing point of a pure solvent and a solution containing a nonelectrolyte.”

Difference between Freezing point of pure solvent ANDFreezing point of solvent + solute/substance

**Adding a solute/substance LOWERS the freezing point.

3) Boiling Point Elevation

Boiling point— Temperature where a liquid’s vapor pressure = atmosphere

pressure

**Boiling point changes result from changes in vapor pressure.

“difference between boiling point of a pure solvent and a solution containing a nonelectrolyte”

Difference between Boiling point of pure solvent AND Boiling point of solvent + solute/substance

Boiling Point and Vapor Pressure

Substances with low vapor pressureMore energy needed for vapor pressure =

atmospheric pressure SOBoiling point INCREASES

** Solutes in a solution LOWER vapor pressure so boiling point INCREASES !

Osmosis

Semipermeable membraneMembrane selects what particles can go through

and blocks other particles

Movement of water through a semipermeable membraneBased on solute concentration (HighLow solute

concentration)

4) Osmotic Pressure

Pressure exerted by solute particles resisting osmosis

INCREASE osmotic pressureHigh solute concentrationWater drawn in

DECREASE osmotic pressure Low solute concentrationWater driven out

Electrolytes and Colligative Properties

Electrolytes GREATLY influence colligative properties. Electrolytes---dissociate into ions in solution Ions increase the NUMBER of solute particles in a

solvent.

Homework Electrolytes Worksheet

Colligative Properties Worksheet