1. Chapter 4 Aqueous Reactions and Solution Stoichiometry
Chemistry, The Central Science, 10th edition
Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten
Chapter 4 Aqueous Reactions and Solution Stoichiometry

2. 4.1 Properties of Aqueous Solutions

3. Solutions (abrev. sol’n)
Homogeneous mixtures of two or more pure substances
can be liquids or gases.
Solvent - substance present in the greatest quantity
Solute(s) - All other substances present in lesser quantities
Solutions in which water is the solvent are called aqueous solutions

4. Water – a great solvent!
H2O molecules can attract, separate, and surround the cations and anions that make up many ionic compounds
Solvation - the process of a solvent surrounding and dissolving an ionic compound  the cations & anions become dissociated (or separated) as they are surrounded by the H2O molecules
The dissociated ions are free to move and become evenly dispersed throughout the solution.
the moving ions can carry a current throughout the solution resulting in electrical conductivity (movement of charged particles through a medium).

5. 1 2
NaCl + H2O 3 4

6. Ionic Compounds in Water
While water is an excellent solvent, not ALL ionic substances will readily dissolve and dissociate in the presence of H2O
Those that DO dissociate are known as electrolytes:
Electrolyte - a substance which contains ions and conducts electricity in it’s aqueous form
There are 3 classifications of electrolytes: strong, weak, and nonelectrolytes

7. * explained on a later slide
Strong Electrolytes
dissociates completely into ions when dissolved in H2O
sol’n exists as 100% ions (no bonded ionic compounds left undissolved)
good conductor of electricity
Includes:
all soluble * ionic compounds
all strong acids & bases*
a few covalent compounds
* explained on a later slide

8. Weak Electrolytes
dissociate only partially into ions when dissolved in H2O
sol’n exists mostly as molecules surrounded by water (very, very few ions present)
poorly conducts electricity
Includes:
weak acids & bases*
(ex: acetic acid, HC2H3O2 [only 1% as ions])
slightly soluble ionic compounds*
some covalent compounds

9. Nonelectrolytes do NOT dissociate into ANY ions
dissolved substance consists of intact molecules surrounded by H2O
does not conduct electricity
Includes:
most covalent compounds (w/the exception of acids & bases which are either strong or weak)

10. Electrolytes: a visual

11. Solubility – ability to be dissolved
Soluble (aq)
a substance which easily dissolves in water
Slightly Soluble (s)
a substance that only dissolves a tiny bit in water
Insoluble (s)
substance that does NOT dissolve in water
substance remains separate from the H2O molecules (no interaction)
substances are insoluble when the ions attract so strongly that they CANNOT be pulled apart by H2O molecules

12. Solubility: a visual

13. Solubility Rules
To know if an ionic substance is soluble or not, you must consult the solubility rules
lists which ions are typically soluble and insoluble
also lists exceptions to the rules
Note: Acids are not explicitly listed in the rules because all acids are aqueous solutions (thus soluble)

14. Solubility Rules for Common Ionic Compounds in Water
Soluble Ionic Compounds
Exceptions: these are insoluble w/ respective anions
Nitrates, NO3-
none
Acetates, C2H3O2-
Chlorides, Cl-
Ag+, Hg22+ (2 Hg atoms), Pb2+
Bromides, Br-
Ag+, Hg22+, Pb2+
Iodides, I-
Sulfates, SO42-
Ag+, Hg22+, Pb2+, Sr2+, Ba2+
Alkali metal cations
Ammonium, NH4+
Insoluble Ionic Compounds
Exceptions: these are soluble w/ respective anions
Sulfides, S2-
alkali metal cations, NH4+, Ca2+, Sr2+, Ba2+
Carbonates, CO32-
alkali metal cations, NH4+
Phosphates, PO43-
Hydroxides, OH-

15. Solubility Rules - Practice
Are the following soluble or insoluble?
Be(C2H3O2)2
MgS
BaSO4
K3PO4
soluble
insoluble
insoluble
soluble

16. Acids
Bases
Substances that produce H+ ions when dissolved in water (Arrhenius).
Ex) HNO3  H+ + NO3–
Substances that produce OH− ions when dissolved in water (Arrhenius).
Ex) NaOH  Na+ + OH–

17. Strong vs. Weak Both strong & weak acids and bases exist
Strong acids & bases dissociate completely in solution
Exist as 100% ions
Strong electrolytes & conductors
Weak acids & bases only partially dissociate in solution
Few ions exits
Weak electrolytes & conductors

18. Strong vs. Weak Electrolytes
Strong Acid: Weak Acid:
HCl HNO2

19. Seven Strong Acids MUST BE MEMORIZED!
Hydrochloric (HCl)
Hydrobromic (HBr)
Hydroiodic (HI)
Nitric (HNO3)
Sulfuric (H2SO4)
Chloric (HClO3)
Perchloric (HClO4)
**When dissolved in water, they dissociate 100% into H+ ions and their respective anion.**

20. Strong Bases MUST BE MEMORIZED!
 Soluble hydroxide compounds
Alkali metal hydroxides
LiOH, NaOH, KOH, etc…
Calcium hydroxide, Ca(OH)2
Strontium hydroxide, Sr(OH)2
Barium hydroxide, Ba(OH)2
When dissolved in water, they dissociate 100% into their respective metal cation and OH–

21. Predicting Ions in Solution
If a substance is soluble, you can predict what ions present are in the solution
Ex) Ammonium sulfate
(NH4)2SO4  soluble
Dissociates into: 2 NH4+ ions
1 SO42- ion
Ex) Sulfuric Acid
H2SO4  soluble
Dissociates into: 2 H+ ions

22. How to Classify Electrolytes
Ask… Is the substance ionic, covalent, or an acid/base?
If ionic, is it soluble?
If soluble = strong electrolyte
If insoluble = nonelectrolyte
If covalent
If covalent and NOT an acid or base = generally nonelectrolyte (ex: sugar, organic compounds)
If acid or a base, is it a strong acid/base?
If strong acid or base = strong electrolyte
if it is any other acid or base = weak electrolyte

23. Classify the following as: strong, weak, or nonelectrolyte
CaCl2
HNO3
Ag3PO4
HCHO2
KOH
C2H5OH
– ionic – soluble = Strong
– acid = Strong
– ionic – insoluble = Nonelectrolyte
– acid = Weak
– ionic – soluble = Strong (also strong base)
– covalent– NOT a base = Nonelectrolyte

24. Classify the following as: strong, weak, or nonelectrolyte
1) Mg(OH)2
2) HCl
3) H3PO4
4) (NH4)2CO3
5) H2SO4
– ionic – insoluble = nonelectrolyte
– strong acid = strong
– weak acid = weak
– ionic – soluble = strong
– strong acid = strong

25. 4.2 Precipitation Rxns

26. Precipitation Rxns
Double replacement reactions that specifically produce a solid product
This solid product is called a precipitate (abbreviated ppt.) and is known as insoluble (because it cannot readily dissolve in water)
To predict if an insoluble ppt will form, use the solubility rules

27. Predicting Precipitations Rxns
Predict the products of the double replacement reaction (cations switch partners)
Use solubility rules to determine the states of matter of the products:
insoluble = (s); soluble = (aq)
If a solid is formed, a ppt rxn has occurred

28. Predicting Precipitation Rxns Practice
1. Fe(NO3)3 (aq) + K2S (aq)
2 Fe(NO3)3 (aq) + 3 K2S (aq) 
Fe2S3 (s) + 6 KNO3 (aq)
2. Li2CO3 (aq) + KC2H3O2 (aq)
Li2CO3 (aq) + KC2H3O2 (aq) 
2 LiC2H3O2 (aq) + K2CO3 (aq)
 NR (no reaction)
= a bunch of ions in a puddle 

29. Will precipitates form?
DEMO!!!
Will precipitates form?
Solutions Used:
0.1 M KI
0.1 M Pb(NO3)2
0.1 M CaCl2

30. Balanced Chemical Equations
Balanced chemical equations show chemical formulas without considering the ionic character of any substances
However… recall that soluble ionic compounds are strong electrolytes
strong acids, strong bases, and soluble ionic salts
This means they dissociate and are truly present as ions in a sol’n
(which leads us to…)

31. …Ionic Equations
Complete Ionic (CIE): explicitly indicates all the IONS that are in sol’n throughout the rxn
Spectator Ions = ions present on BOTH sides of the chemical equation
Ions are present but play NO DIRECT ROLE in chemical rxn
When ALL reactants and products are AQUEOUS (no reaction), every ion is a spectator ion (so CIE is not usually written)

32. …Ionic Equations Net Ionic (NIE):
includes only ions and compounds directly involved in the chemical rxn
This means NO spectators are included

33. CIE & NIE Practice Mg(NO3)2 (aq) + Li2SO4 (aq) Balanced Equation:
Mg(NO3)2 (aq) + Li2SO4 (aq)  MgSO4 (aq) + 2 LiNO3 (aq) = NR
Complete Ionic Equation:
Mg2+ (aq) + 2 NO3- (aq) + 2 Li+ (aq) + SO42- (aq)
 Mg2+ (aq) + SO42- (aq) + 2 Li+ (aq) + 2 NO3- (aq)
Net Ionic Equation:
NONE! – all spectators

34. CIE & NIE Practice (NH4)3PO4 (aq) + BaS (aq) Balanced Equation:
 3 (NH4)2S (aq) + Ba3(PO4)2 (s)
Complete Ionic Equation:
Net Ionic Equation:
2 PO43- (aq) + 3 Ba2+ (aq)  Ba3(PO4)2 (s) … NO spectators!
6 NH4+ (aq) + 2 PO43- (aq) + 3 Ba2+ (aq) + 3 S2- (aq)
 6 NH4+ (aq) + 3 S2- (aq) + Ba3(PO4)2 (s)

35. 4.4 Oxidation-Reduction Reactions

36. Single Replacement Rxns
General Rxn Formula:
A + BC  AC + B
The reactants:
One reactant is a single element by itself
The other reactant is an ionic compound
The products:
If the single element is a metal, it will replace the cation in the ionic compound
If the single element is a halogen gas, it will replace the anion in the ionic compound

37. Oxidation-Reduction Rxns (aka: Redox)
All single replacement rxns can be classified as Redox rxns (but not all redox rxns are single replacement)
Redox rxns occur when electrons are transferred between reactants
Oxidation occurs when an atom, ion, or molecule loses electrons. (LEO)
Reduction occurs when an atom, ion, or molecule gains electrons. (GER)
* Both processes happen simultaneously in a rxn

38. Activity Series of Metals - Ease of Oxidation
When a single replacement rxn occurs, the metal that is alone will be oxidized.
However, some metals are easier to oxidize than others (they lose electrons more easily than others, thus forming cations)
Active Metals:
metals at the top of the activity series are more reactive and more easily oxidized
Noble Metals:
metals at the bottom of the activity series which have very low reactivity

39. Activity Series of Metals
In a single replacement rxn:
a solid metal element can be OXIDIZED by any elements listed below it in the activity series
Look to see if the metal solid is ABOVE the metal cation (in the 2nd reactant)
If yes, the rxn does happen  predict products
If not, NR (b/c the solid metal cannot be oxidized)
Activity Series of Metals

40. Using the Activity Series Examples
1) magnesium sulfate+ zinc metal
2) iron metal + copper (II) nitrate
 NR
Fe (s) + Cu(NO3)2 (aq)  Cu (s) + Fe(NO3)2
We can also write CIE & NIE!!! (only aqueous dissociate)
CIE: Fe (s) + Cu2+ (aq) + 2 NO3– (aq)
 Cu (s) + Fe2+ (aq) + 2 NO3– (aq)
NIE: Fe (s) + Cu2+ (aq)  Cu (s) + Fe2+ (aq)

41. Metals Reacting w/Acids
Only metals listed ABOVE hydrogen in the series are able to react with acids
If the reaction does occur, H2 gas is produced.
Example #1:
___Ni (s) + ___HCl (aq) 
Ni is above H2, so the rxn occurs!
Example #2:
___Cu (s) + ___HCl (aq) 
Cu is below H2, so no rxn occurs!
NiCl2(aq) + H2 (g) 2 NR

42. Activity Series of Halogens:
The idea is the same here…
Fluorine is the most reactive
Iodine is the least reactive
Only a MORE reactive halogen can replace a LESS reactive one
In these single replacement rxns, the single element (halogen gas) must be listed ABOVE the halogen anion in the 2nd reactant for a rxn to occur
___Cl2 + ___NaBr (aq) 
Activity Series of Halogens:
Fluorine
Chlorine
Bromine
Iodine
___NaCl (aq) + ___Br2 (g) 2 2