Solutions

Solutions

Homogeneous mixtures of 2 or more substances

Can be:

Solid Sterling

SilverGas

Air

Liquid

**Used most

frequently

in

chemistry**

Solution Components:

Solvent

Solute

the component present in the greatest amount

all other components dissolved in solvent

Aqueous Solutions

Solvent

Solute

WATER

Whatever is dissolved in the water

In chemical equations, denoted as aqueous (aq)

WATERUniversal solvent

POLAR molecule

Oxygen has higher electronegativity than Hydrogen so it pulls the bonded electrons closer to it giving it a partial negative charge

δ+

δ+

δ-

How things dissolve in

1) Ionic

Compounds

(Salts)

Ionic compounds dissociate into component

ions & surrounded by water molecules

(solvated)

WATER

Compound of cation & anion (normally metal + nonmetal)

How things dissolve in

2) Covalent

Compounds

(Molecules)

WATERCompounds of nonmetals

Molecular substances dissolve without forming ions -water molecules surround molecules

*EXCEPTION: Acids/Bases

How things dissolve in

3) Acids & BasesWATER

Form IONS in solution

Acids usually have Hydrogen at start of chemical formula or contains COOH group

STRONG ACID/BASES

WEAK ACID/BASES

Completely dissociate

Partially dissociate

Electrolyte & NonelectrolyteElectrolyte: a substance whose aqueous solutions contains ions

Nonelectrolyte: a substance whose aqueous solutions does not contain ions

Ions are able to carry electrical charge to and from electrodes—conduct electricity

No ions to carry electrical charge to and from electrodes— do not conduct electricity

Nonelectrol

yte

Strong

electrolyteWeak

electrolyte

Identifying ElectrolytesStrong electrolyteWeak electrolyteNonelectrolyte

Ionic

Molecular

All None None

Strong Acids

Weak Acids/Base

s

All other compounds

Strong Acids Strong BasesHClHBrHIHClO3HClO4HNO3H2SO4 (first proton)

Group 1A metal HydroxidesHeavy Group 2A Hydroxides

[Ca(OH)2, Sr(OH)2, Ba(OH)2]

Equations of Strong/Weak Electrolytes

HCl (aq)

H+ (aq)+ Cl- (aq)

CH3COOH (aq) H+ (aq)+ CH3COO- (aq)

Half arrows in opposite direction indicate chemical equilibrium- forward reaction

is equal to rate of backward reaction

In this case, molecules are ionizing and ions are recombining to form molecules

BaF2

*water molecules not shown for simplicity*

2+

- 2+2

+

2+

-

--

-

--

Electrolyte or Nonelectrolyte?

Strong or Weak?

Ions present?

-Ba2+

F-

STOP

Electrolyte or Nonelectrolyte?

Strong or Weak?POP QUIZ

Solution of:MgCl2

KClK2SO4

*water molecules not shown for simplicity*

2-

2- 2-

2-

+ +

+

+

+

++

+Extra Credit: Write the correctly balanced electrolyte equation that the picture could represent.

Precipitate ReactionsReaction in which two aqueous solutions produce an insoluble product called a precipitate

KI (aq) + Pb(NO3)2 (aq)KNO3 (aq) + PbI2 (s)

Solubility RulesSoluble Compounds Contain:C2H3O2 - , CH3COO-

NH4+

NO3-

CN-

ClO-

ClO2-

ClO3-

ClO4-

Br-

Cl-

I-

SO4-2

Common Exceptions:NoneNoneNoneNoneNoneNoneNoneNone

Compounds of Ag+, Pb2+, Hg2+2

Compounds of Ag+, Pb2+, Hg2+2

Compounds of Ag+, Pb2+, Hg2+2

Compounds of Sr+2, Ba+2, Pb+2, Hg2+2

Insoluble Compounds Contain:CO3

-2

PO4-3

CrO4-2

Cr2O7-2

OH-

S-2

Common Exceptions:Compounds of NH4

+ & Alkali MetalCompounds of NH4

+ & Alkali MetalCompounds of NH4

+ & Alkali MetalCompounds of NH4

+ & Alkali MetalCompounds of NH4

+ Alkali Metal, Ca+2, Sr+2, and Ba+2

Compounds of NH4+ Alkali Metal, Ca+2, Sr+2, and Ba+2

Ag2SO4 (aq) + Na(NO3) (aq)

2-

2-

+

++

+

- +-

- -+

+

+

+ 2-

2-

+

++

+-

+-

--

+

+

+

Both products soluble= no reaction

Ionic Equations & Spectator Ions2KI(aq) + Pb(NO3)2(aq) PbI2(s) + 2KNO3 (aq)Chemical Equation: shows chemical formulas without indicating ionic character

Complete Ionic Equation: all soluble strong electrolytes shown as ions2K+(aq) + 2I-(aq)+ Pb2+(aq)+2NO3

-(aq) PbI2(s)+2K+

(aq)+2NO3-(aq)

Net Ionic Equation: only the ions and compounds directly involved in reaction shown

Ions that appear in identical form on both sides of ionic

equation are called spectator ions- they don’t play a role in the reaction

2I-(aq)+ Pb2+(aq) PbI2(s)

Which ions if any, are spectator ions in this reaction?NaCl(aq) + AgNO3(aq) AgCl(s) +

NaNO3 (aq)

STOP

Concentration of SolutionsConcentration: amount of solute dissolved in given quantity of solvent or quantity of solution

Molarity (M)Way to measure the concentration of a solutionNumber of moles of solute in a liter of solution

moles solutevolume of soln

(L)Molarity =

molV

M =

Practice!Calculate the molarity of a solution made by dissolving 23.4g of sodium sulfate in enough water to form 125mL of solution.

Converting between molarity, moles & volume

molV

M =

Practice!A solution of HNO3 has a concentration of 0.200M; how many moles does a 2.0L solution contain?

Making Solutions•Mass appropriate amount of solute•Add to container (volumetric flask, beaker, Erlenmeyer flask etc)•Add water, swirl to dissolve•Continue to add water until required volume of solution reached

DilutionProcess of making a lower concentration solution from a higher concentrated solution.

HOW???Add WATER

Dilution**Since you’re not changing the amount of solute:**

Mol of solute before dilution = mol of solute after dilution

molV

M =

M1V1 =M2V2

Practice!How many milliliters of 3.0M H2SO4 are needed to make 450mL of 0.10 M H2SO4?