SolutionsSolutions

Parts of SolutionsParts of Solutions

Solution-Solution- homogeneous mixture.

SoluteSolute- what gets dissolved. SolventSolvent- what does the

dissolving. SolubleSoluble- Can be dissolved.

Aqueous solutionsAqueous solutions

Dissolved in water. Water is a good solvent

because the molecules are polar.

The oxygen atoms have a partial negative charge.

The hydrogen atoms have a partial positive charge.

HydrationHydration The process of breaking the ions of

salts apart. Ions have charges and attract the

opposite charges on the water molecules.

HydrationHydration

H HOH

H OH

HO

H HO

HHO

HH

O

HH

OH

H

O

HH

O

ElectrolytesElectrolytes

Electricity is moving charges. The ions that are dissolved can

move. Solutions of ionic compounds can

conduct electricity and are called electrolyteselectrolytes. Solutions are classified three ways.

Types of solutionsTypes of solutions

Strong electrolytesStrong electrolytes- completely dissociate (fall apart into ions).

Many ions- Conduct well. Weak electrolytesWeak electrolytes- Partially fall apart

into ions. Few ions -Conduct electricity slightly. Non-electrolytesNon-electrolytes- Don’t fall apart. No ions- Don’t conduct.

Making solutionsMaking solutions

What solute and the solvent are determines• Whether a substance will dissolve.• How much will dissolve.

A solid substance dissolves faster if-

It is stirred or shaken.The particles are made smaller.The temperature is increased.

How Much?How Much? SolubilitySolubility- The maximum amount of

substance that will dissolve at that temperature (usually g/L).

Saturated solutionSaturated solution- Contains the maximum amount of solid dissolved.

Unsaturated solutionUnsaturated solution- Can dissolve more solute.

Supersaturated-Supersaturated- A solution that is temporarily holding more than it can, a seed crystal will make it come out; forms a precipitate

LiquidsLiquids

MiscibleMiscible means the that to liquids can dissolve in each other.

ImmiscibleImmiscible means they can’t

What affects What affects solubility?solubility?

Temperature Pressure The polarity of the solvent

• polar and ionic compounds dissolve in polar solvents such as water

• non-polar solutes dissolve in non-polar solvents such as alcohol

Remember !!!Remember !!!

““Like dissolves Like dissolves Like”Like”

What affects What affects solubility?solubility?

For solids in liquids as the temperature goes up the solubility goes up.

For gases in a liquid as the temperature goes up the solubility goes down.

For gases in a liquid- as the pressure goes up the solubility goes up.

The Solubilities The Solubilities of Several Solids of Several Solids as a Function of as a Function of

TemperatureTemperature

While most substances become more soluble in water with increased Temperature, sodium sulfate and cerium sulfate do not

Pressure Pressure

Changing the pressure doesn’t effect the amount of solid or liquid that dissolves

They are incompressible. However, it does effect gases.

Dissolving GasesDissolving Gases

Pressure effects the amount of gas that can dissolve in a liquid.

The dissolved gas is at equilibrium with the gas above the liquid.

Gases are predictableGases are predictable

As temperature increases, solubility decreases.

Gas molecules can move fast enough to escape.

The gas is at equilibrium with the dissolved gas in this solution.

The equilibrium is dynamic.

If you increase the pressure the gas molecules dissolve faster.

The equilibrium is disturbed.

The system reaches a new equilibrium with more gas dissolved.

The Solubilities The Solubilities of Several Gases of Several Gases in Waterin Water

Solubility RulesSolubility Rules

See handoutSee handout

Measuring SolutionsMeasuring Solutions

ConcentrationConcentration A measure of the amount of solute

dissolved in a certain amount of solvent.

Concentrated solution has a large amount of solute.

Dilute solution has a small amount of solute.

Expressed as g/L. But chemical reactions don’t happen in

grams

MolarityMolarity

The number of moles of solute in 1 Liter of the solution.

M = moles/Liter What is the molarity of a solution

with 2.0 moles of NaCl in 4.0 Liters of solution.

.50 mol/L

Making solutionsMaking solutions Pour in a small amount of solvent Then add the solute and dissolve it Then fill to final volume. M x L = moles How many moles of NaCl are

needed to make 6.0 L of a 0.75 M NaCl solution?

4.5 mol

DilutionDilution

Adding water to a solutionAdding water to a solution

DilutionDilution The number of moles of solute doesn’t

change if you add more solvent. The moles before = the moles after M1 x V1 = M2 x V2 M1 and V1 are the starting

concentration and volume. M2 and V2 are the final concentration

and volume. Stock solutions are pre-made to known

M.