1. Reactions and Solution Stoichiometry
AP Chem - Unit 2
Reactions and Solution Stoichiometry

3. Types of Reactions Combination (Synthesis) Decomposition Combustion
Single Replacement
Double Replacement (Metathesis)

4. Combination/Synthesis
Basic Form
A + B  AB
Rxns of elements with oxygen and sulfur
C(s) + O(s)  CO2 (g)
Rxns of metals with halogens
2Na(s) + Cl2 (g)  2NaCl
Synthesis rxns with oxides
CaO(s) + H2O (l)  Ca(OH)2 (s)

5. Decomposition Basic Form AB  A + B Binary compounds
2H2O (l)  2H2 (g) + O2 (g)
Metal hydroxides
Cu(OH)2 (s)  CuO(s) + H2O (l)

6. More Decomposition Examples
Metal carbonates
PbCO3 (s)  PbO (s) + CO2 (g)
Metal chlorates
2KClO3 (s)  2KCl (s) + 3O2 (g)
Oxyacids
H2CO3 (l)  H2O (l) + CO2 (g)

7. Combustion
A substance combines with oxygen, releasing a large amount of energy in the form of light and heat.
True or False: The products of every combustion reaction are CO2 and H2O
False

8. Combustion Examples Reactive elements combine with oxygen
P4(s) + 5O2(g)  P4O10(s)
(This is also a synthesis reaction)
The burning of natural gas, wood, gasoline
C3H8(g) + 5O2(g)  3CO2(g) + 4H2O(g)

9. Single Replacement Basic Form A + BY  AY + B Metals by other metals
3Mg + 2FeCl3  2Fe + 3MgCl2
Hydrogen in water by another metal
2Na +2H2O  H2 + 2NaOH

10. More Single Replacement
Hydrogen in an acid by another metal
2Li + 2HCl  H2 + 2LiCl
Halogens by more active halogens
Cl2 + 2KI  I2 + 2KCl

11. The Activity Series of the Metals
Lithium
Potassium
Calcium
Sodium
Magnesium
Aluminum
Zinc
Chromium
Iron
Nickel
Lead
Hydrogen
Bismuth
Copper
Mercury
Silver
Platinum
Gold
Metals can replace other metals
provided that they are above the
metal that they are trying to
replace.
Metals above hydrogen can
replace hydrogen in acids.
Metals from sodium upward can
replace hydrogen in water

12. The Activity Series of the Halogens
Fluorine
Chlorine
Bromine
Iodine
Halogens can replace other
halogens in compounds, provided
that they are above the halogen
that they are trying to replace.
2NaCl(s) + F2(g) 
2NaF(s) + Cl2(g)
MgCl2(s) + Br2(g) 
???
No Reaction

13. Double Replacement (Metathesis)
Basic Form
AX + BY  AY + BX
One of the compounds formed is usually a precipitate, an insoluble gas that bubbles out of solution, or a molecular compound, usually water.
How do you tell if a precipitate will form?
Use your Solubility Rules!!!

14. Mostly Soluble Ion Solubility Exceptions NO3- Soluble None ClO4- Na+K+
NH4+
Cl-, I-
Pb2+, Ag+, Hg22+
SO42-
Ca2+, Ba2+, Sr2+, Pb2+, Ag+, Hg2+

15. Mostly Insoluble Ion Solubility Exceptions CO32- Insoluble
Group IA and NH4+
PO43-
OH-
Group IA and Ca2+, Ba2+, Sr2+
S2-
Groups IA, IIA, and NH4+

16. The Solubility Rule Song!!!!
(Sing to Rhythm of 99 Bottles)
 Alkali metals 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, mercury one
And chloride of lead
Every single sulfate
Is soluble, 'Tis said
'Cept barium, strontium, mercury one And calcium and lead. -
Hydroxides in general
don't dissolve at all
But, barium, strontium and calcium
Are slightly soluble
*but don't forget *
Alkali metals and ammonium salts
Whatever they may be
Can always be depended on
For solubility 
The carbonates are insoluble,
It's lucky that it is so,
Or else, our marble buildings
Would melt away like snow.
*but, once again, don't forget *
For solubility

17. Spectator Ions do NOT participate in the reaction
Net Ionic Equations
Written to show only the species that react or undergo change in aqueous solution.
Steps for writing net ionic equations
Write a balanced molecular equation
Rewrite the equation to show the ions that form in solution
Identify and cancel spectator ions
Spectator Ions do NOT participate in the reaction

18. Sample Problem
What compound precipitates when solutions of Fe2(SO4)3 and LiOH are mixed? Write the complete chemical reaction for the reactants above. Write the net ionic equation. List any spectator ions.

19. Another Type of Metathesis
Acid/Base Reactions
Two Types
Neutralization
HCl + NaOH  NaCl + H2O
Gas Formation
2HCl +Na2S  H2S(g) + 2NaCl
HCl + NaHCO3  NaCl + H2CO3
H2CO3  H2O + CO2(g)

20. Oxidation Reduction Rxns
Electrons are transferred
Oxidation = Loses Electrons
Reduction = Gains Electrons
OIL RIG
LEO goes GER!! OR

21. Redox Rxn Each sodium atom loses one electron atom gains one electron:
Each chlorine atom gains one electron:

22. LEO says GER :
Lose Electrons = Oxidation
Sodium is oxidized
Gain Electrons = Reduction
Chlorine is reduced

23. OIL RIG:
Oxidation Is Loss of electrons
Sodium is oxidized
Reduction Is Gain of electrons
Chlorine is reduced

24. Reducing Agents and Oxidizing Agents
The substance reduced is the oxidizing agent
The substance oxidized is the reducing agent
Sodium is oxidized – it is the reducing agent
Chlorine is reduced – it is the oxidizing agent

25. Rules for Assigning Oxidation #s
Atoms in elemental form are always zero
Monatomic ions equal the charge on the ion
Oxygen is usually -2 (except peroxide is -1)
Hydrogen is +1 with NM and -1 with M
Fluorine is always -1
Sum of the ox #s of all atoms in a neutral compound is zero
Sum of the ox #s in a polyatomic ion = the ion charge

26. Sample Problem H2S S8 SCl2 Na2SO3 SO42-
Determine the oxidation #s for the following:
H2S S8
SCl2
Na2SO3
SO42-

27. Oxidation of metals by acids and salts
Similar to single replacement rxns, sometimes called Displacement Rxns
General form
A + BX  AX + B
Examples
Zn(s) + 2HBr (aq)  ZnBr2(aq) + H2 (g)
Mn(s) + Pb(NO3)2(aq)  Mn(NO3)2 (aq)+ Pb(s)

28. Rules for Balancing Redox Rxns
Assign oxidation #s
Determine which species are being oxidized or reduced
Divide the equation into 2 half-reactions
Balance each half reaction
Balance elements other than H and O
Balance O by adding water as needed
Balance H by adding H+ as needed
Balance charge by adding e-
Multiply half reactions by integers so # of e- are the same in each reaction
Add half reactions together, simplifying when you can
Check to see if equation is charge and mass balanced

29. Sample Problem Balance the following
MnO4-(aq) + C2O42-(aq) Mn2+(aq) + CO2(aq)

30. Other Rxns Metal Oxide in Water Nonmetal Oxide in Water MO + H2O  MOH
BaO + H2O  Ba(OH)2
Nonmetal Oxide in Water
NO + H2O  oxyacid
N2O3 + H2O  HNO2

31. Solutions

32. Solute Solvent A solute is the dissolved substance in a solution.
Salt in salt water
Sugar in soda drinks
Carbon dioxide in soda drinks
Solvent
A solvent is the dissolving medium in a solution.
Water in salt water
Water in soda

33. Definition of Electrolytes and Nonelectrolytes
An electrolyte is:
A substance whose aqueous solution conducts
an electric current.
A nonelectrolyte is:
A substance whose aqueous solution does not
conduct an electric current.
Try to classify the following substances as
electrolytes or nonelectrolytes…

34. Which of the following are electrolytes?
Pure water
Tap water
Sugar solution
Sodium chloride solution
Hydrochloric acid solution
Lactic acid solution
Ethyl alcohol solution
Pure, solid sodium chloride

35. Answers… ELECTROLYTES: NONELECTROLYTES: Tap water (weak) NaCl solution
  HCl solution
  Lactate solution (weak)
  Pure water
  Sugar solution
  Ethanol solution
  Pure, solid NaCl

36. Electrolytes & Net Ionic Equations
Ionic CompoundsDissociate
NaCl(s)  Na+(aq) + Cl-(aq)
AgNO3(s)  Ag+(aq) + NO3-(aq)
MgCl2(s)  Mg2+(aq) + 2 Cl-(aq)
Na2SO4(s)  2 Na+(aq) + SO42-(aq)
AlCl3(s)  Al3+(aq) + 3 Cl-(aq)
These compounds should be written as ions in net ionic equations.

37. Strong acids such as HCl are completely ionized in solution
Strong acids such as HCl are completely ionized in solution. So they are written as ions in the net ionic equation
Other examples of strong acids include:
Sulfuric acid, H2SO4
Nitric acid, HNO3
Hydriodic acid, HI
Perchloric acid, HClO4
Weak acids such as lactic acid usually ionize less than 5% of the time. So they are not written as ions in the net ionic equation.

38. Molarity
The concentration of a solution measured in moles of solute per liter of solution.
mol = M L

39. Sample Problem
How many grams of sodium chloride are needed to prepare 1.50 liters of M NaCl sol’n?

40. Serial Dilution
It is not practical to keep solutions of many different concentrations on hand, so chemists prepare more dilute solutions from a more concentrated “stock” solution.
MstockVstock = MdiluteVdilute

41. Sample Problem
What volume of stock (11.6 M) hydrochloric acid is needed to prepare a 3.0 M ml solution?

42. Sample Problem
How many grams of Ca(OH)2 are needed to neutralize 25.0 mL of M HNO3?

43. Sample Problem
A sample of 70.5 mg of potassium phosphate is added to 15.0 mL of M silver nitrate, resulting in the formation of a precipitate.
Write the molecular equation for the reaction
What is the limiting reactant?
Calculate the theoretical yield, in grams, of the ppt that forms.

44. Sample Problem
45.7 mL of H2SO4 is required to neutralize a 20.0 mL sample of NaOH solution. What is the concentration of the NaOH solution?