Ch. 4.1 & 4.2Properties of Aqueous Solutions,

Precipitation Reactions

4.1 Aqueous solutions – solutions in water

Can conduct electricity How well it does so is based on # of ions

in solution More ions = easier to conduct

3 types of solutions Strong electrolytes Weak electrolytes Nonelectrolytes

4.1

(a) Ionic compound dissolving in water

(b) Molecular compound dissolving in water

4.1 Ionic compounds

Cations, anions dissociate in water Each ion surrounded by water molecules Ions in solution allows flow of current

Pure water doesn’t conduct electricity Ions in water are what cause people to get

electrocuted/shocked (ouch!)

4.1 Molecular compounds

Can dissolve, but don’t break apart…so no ions

No ions = no conducting electricity Ex. Salt water = conductor, sugar water ≠

conductor

4.1 Strong vs. weak electrolytes

Strong – completely dissociate (fall apart) in solution Ex. HCl(aq) H+(aq) + Cl-(aq)

Weak – partial dissociation, small concentration of ions Dissociated ions in equilibrium

with un-ionized compound Ex. HC2H3O2(aq) ⇌ H+(aq) +

C2H3O2-(aq)

4.2 Two solutions (aqueous) mixed and solid

is formed Solid called precipitate Rxn where precipitate formed =

precipitation reaction

4.2 Solubility rules – MUST KNOW THESE!

Common Group 1, ammonium (NH4+) salts

are soluble Nitrates (NO3

-), chlorates (ClO4-), acetates

(C2H3O2-) are soluble (except AgC2H3O2)

Halide salts (except fluorides) are soluble except those of Ag, Hg2

2+, and Pb SO4

2- soluble except with Ag, Hg, Pb, Ca, Sr, Ba

Group 1, Ca, Sr, and Ba hydroxides (OH-) are soluble, the others are typically not

Other ionic compounds = insoluble

4.2

4.2 How will I remember all of those?!

Easier way: solubility song!

4.2Rules For Solubility

(Taken from Cornell University - Chemistry Department) (Sing to Rhythm of 99 Bottles) 

Potassium, sodium, and ammonium salts, Whatever they may be, Can always be depended on For solubility. 

When asked about the nitrates The answer is always clear, They each and all are soluble, Is all we want to hear. 

Most every chloride's soluble At least we've always read Save silver, mercurous mercury And (slightly) chloride of lead.

Every single sulfate is soluble,'Tis said ‘cept barium and strontium And calcium and lead. 

Hydroxides of metals won't dissolve That is, all but three Potassium, sodium and ammonium Dissolve quite readily.

And then you must remember That you must not "forgit" Calcium, barium, strontium Dissolve a little bit. 

The carbonates are insoluble, It's lucky that it's so, Or else, our marble buildings Would melt away like snow. 

(Repeat with feeling) Potassium, sodium, and ammonium salts Whatever they may be, Can always be depended on For solubility.

…AND YES, WE ARE GOING TO MEMORIZE THIS! YAY!

YouTube – Solubility Song

4.2 Double Replacement/Displacement

(Metathesis) Reactions (…many names, the same thing…) Swapping of ions Ex. AX + BY AY + BX

In solution, a chemical change will occur if… Precipitate forms Weak electrolyte forms Insoluble gas forms (it will bubble out)

4.2 Molecular equation – all species listed as

molecules Ex. HCl(aq) + NaOH(aq) H2O(l) +

NaCl(aq)

Complete ionic equation – lists all ions Ex. H+(aq) + Cl-(aq) + Na+(aq) + Cl-(aq) H2O(l) + Na+(aq)

+ Cl-(aq)

Net ionic equation – lists only unique ions (no spectators) H+(aq) + OH-(aq) H2O(l)

4.2 To determine if reaction is occurring in solution…

AgNO3(aq) + KCl(aq) ???

1. Separate ions Ag+ + NO3

- + K+ + Cl-

2. Determine all possible compounds formed KNO3, AgCl

3. Determine which (if any) of the compounds will form a precipitate (a.k.a. are insoluble) KNO3 soluble; AgCl insoluble

Write your chemical reaction without “spectator ions” Ag+(aq) + Cl-(aq) AgCl(s)

4.2 Your turn!

Write the complete ionic and net ionic equations for the following reactions: Aqueous solutions of sodium sulfide and

calcium nitrate are mixed. Aqueous solutions of barium chloride and

potassium sulfate are mixed. Aqueous solutions of silver nitrate and

ammonium chloride are mixed.