1. Predicting Reactions Presented by Mr. Mark Langella
AP Chemistry Instructor
College Board Consultant

2. Why do the reactions occur?
Gibbs Free Energy drives the Spontaneous reactions
Lower PE energy
Formation of Stronger Bonds
Greater Entropy ( Formation of Gases)
Solubility
Formation Constant

3. Ways of Expressing CHEMICAL EQUATIONS
Word equation
In word equations, the names of the reactants and products are written out. The following example is a word equation:
carbon + oxygen carbon dioxide

4. Formula equations
Formula equations consist of formulas substituted for the names in the word equation. The reaction above becomes
C + O CO2

5. Ionic equations
In ionic equations, all water soluble compounds in an aqueous solution are separated into ions.
2NaI(aq) + Pb(NO3)2(aq) NaNO3(aq) + PbI2(s)
2Na+(aq) + 2I-(aq) + Pb2+(aq) + 2NO3-(aq) 2Na+(aq) + 2NO3-(aq) + PbI2(s)
Spectator ions - Spectator ions do not participate in the chemical reaction. That is, they are identical on both sides of the equation.

6. Net ionic equations
The net ionic equation contains all of the particles in the ionic equation less any spectator ions.
2Na+(aq) + 2I-(aq) + Pb2+(aq) + 2NO3-(aq) Na+(aq) + 2NO3-(aq) + PbI2(s)
Pb2+(aq) + 2I-(aq) PbI2(s)

7. Examples
1. A strip of magnesium metal is added to an aqueous solution of silver nitrate.         Question: Which substance is oxidized in the reaction? 2. Solid potassium chlorate is strongly heated.         Question: What is the oxidation number of chlorine before and after the reaction occurs? 3. Solid silver chloride is added to a solution of concentrated hydrochloric acid to form a complex ion.         Question: Which species acts as a Lewis base in the reaction?  Explain. 4.  A solution of ethanoic (acetic) acid is added to a solution of barium hydroxide.         Question: Explain why a mixture of equal volumes of equimolar solutions of acetic acid and barium hydroxide is basic.

8. Examples
5. Ammonia gas is bubbled into a solution of hydrofluoric acid.         Question: Identify a conjugate acid-base pair in the reaction. 6. Zinc metal is placed into a solution of copper (II) sulfate.         Question: Describe the change in color that the original solution undergoes as the reaction proceeds. 7. Hydrogen phosphide (phosphine) gas is added to boron trichloride gas.         Question: Which species acts as a Lewis acid in the reaction? Explain.

9. Examples
8. A solution of nickel (II) bromide is added to a solution of potassium hydroxide.         Question: Identify the spectator ions in the reaction mixture. 9. Hexane is combusted in air.         Question: When one molecule of hexane is completely combusted, how many molecules of products are formed?

10. Balancing
We were reminded (especially by the combustion reaction above) that the coefficients used for balancing should be the lowest possible WHOLE NUMBER coefficients.  
All other rules for the balanced equations are the same - omit spectator ions, assume a reaction occurs, write the formulas for molecular compounds (e.g. HF) as undissociated species in solution, etc.

11. Synthesis or Combination Reactions
In synthesis or combination reactions, two or more substances combine together to form a single product.
The general form is A + B C
The products must contain only those elements found in the reactants.

13. Metal + Nonmetal Salt Magnesium ribbon is burned in oxygen
A strip of magnesium metal is heated strongly in pure nitrogen gas

14. Online Demos Reaction of Magnesium and Oxygen
Reaction of Iron and Sulfur
Reaction of Potassium and Oxygen
Reaction of Lithium and Oxygen
Reaction of Lithium and Chlorine
Reaction of Sodium and Oxygen
Reaction of Zinc and Sulfur

15. Nonmetal + Nonmetal Molecular compounds
Pure Solid Phosphorus (White Form) is burned in air
Reaction of Phosphorus and Chlorine
Website:

16. Reaction of Hydrogen and Oxygen

18. Hydrides Preparation of the Group 1 hydrides
These are made by passing hydrogen gas over the heated metal. For example, for lithium hydride:
2Li (s) + H2(g) LiH

19. Nonmetal Oxide + Water Oxyacid
Oxy Acid= Contains H+ ions attached to common Polyatomic ion of Nonmetal Oxide plus one more oxygen
Solid dinitrogen pentoxide is added to water
Sulfur trioxide gas is bubbled into water

20. Phosphorus(V) oxide powder is sprinkled over dis­tilled water
Sulfur dioxide gas is bubbled into distilled water

22. Metal oxide + water metal hydroxide
Solid Cesium Oxide is added to water
Solid sodium oxide is added to distilled water
Powdered strontium oxide is added to distilled water
Calcium oxide powder is added to distilled water
Solid barium oxide is added to distilled water

23. Demo

24. Cmd
Na2O
MgO
Al3O2
SiO2
P4O10
SO3
Cl2O7
%Ionic 79 68 56 45 32 17 2
Solid
Ionic
Network
Molecular
Hydroxide Formula
NaOH
Mg(OH)2
Al(OH)3
Si(OH)4
OP(OH)3
O2S(OH)2
O3Cl(OH)
Formula
SiO2+2H2O
H3PO4
H2SO4
HClO3
Very Basic
Basic
Ampho.
Slightly acidic
Acidic
Stronger Acid
Very Acidic

25. Hydrogen-Nonmetal + Water Acidic Solution
Hydrogen Chloride gas bubbled into water

26. Metal oxide + carbon dioxide metal carbonate
Metal oxide + nonmetal oxide metal ion attached to common polyatomic ion
Metal oxide + carbon dioxide metal carbonate
Carbon dioxide gas is passed over hot, solid sodium oxide
Metal oxide + sulfur dioxide Metal sulfite
Sulfur Dioxide is passed over solid calcium oxide

27. DECOMPOSITION REACTIONS
Substances break down by means of decomposition reactions
The general form of a decomposition reaction is
C A + B
Decomposition reactions are the opposite of combination or synthesis reactions

28. Decomposition of Metal Carbonate
Heating a metal carbonate always yields the metal oxide and carbon dioxide.
MCO MO + CO2
Powdered magnesium carbonate is heated strongly
Solid calcium carbonate is strongly heated

29. Metal Hydrogen Carbonate Decomposition
Heating a metal bicarbonate gives the metal oxide, carbon dioxide, and water.
MHCO3 MO + H2O + CO2
Solid Sodium Hydrogen Carbonate is strongly heated

30. Heating the nitrates
Most nitrates tend to decompose on heating to give the metal oxide, brown fumes of nitrogen dioxide, and oxygen.
For example, a typical Group 2 nitrate like magnesium nitrate decomposes like this:
In Group 1, lithium nitrate behaves in the same way - producing lithium oxide, nitrogen dioxide and oxygen.
The rest of the Groups, however, don't decompose so completely (at least not at Bunsen temperatures) - producing the metal nitrite and oxygen, but no nitrogen dioxide.
2 Mg(NO3)2 = MgO NO O2

31. Decomposition of Metal Hydroxides
Heating a metal hydroxide gives the metal oxide and water
MOH MO + H2O

32. Metal Sulfite Decomposition
Heating a metal sulfite produces a metal oxide and sulfur dioxide
MSO3 MO + SO2
Solid calcium sulfite is heated in a vacuum

33. Metal Chlorate Decomposition
Heating a metal chlorate gives the metal chloride plus oxygen.
MClO MCl + O2

34. Electrolysis of Binary Compound
Electrolysis of a molten salt (ionic compound) separates the substance into its elements.
MN M + N

35. Ammonium Compound Decomposition
Ammonium Carbonates
Solid ammonium carbonate is heated
Ammonium Hydroxide
(NH4)2CO3 = 2NH CO H2O

36. 2007 Questions
(NH4)2CO3 = 2NH CO H2O

38. Peroxide Decomposition
Elephant’s Toothpaste
Website:
Genie in a Bottle Demo
Website:

40. Reactions Based on Reduction Potentials EMF Potential
Reduction and Oxidation
Single replacement

41. Cation Replacement
There are two types of single replacement reactions, in one, a metal or hydrogen replaces a positive ion
M0 + A+B- M+B- + A0

44. Replacement of Hydrogen
Reaction of Magnesium and Different Concentrations of Acids
Website:
Hydrochloric Acid(g) + Magnesium(s)  Magnesium(II)Chloride(aq) + Hydrogen(g)
2HCl(g) + Mg(s)  MgCl2(aq) + H2(g)
Small piece of sodium metal is added to distilled water
Website:
Sodium(s) + Water(l)  Sodium Hydroxide(aq) + Hydrogen(g)
2Na(s) + 2H2O(l)  2NaOH(aq) + H2(g)

45. ) Reaction of Potassium and Water
Website:
Potassium(s) + Water(l)  Potassium Hydroxide(aq) + Hydrogen(g)
2K(s) + 2H2O  2KOH + H2(g)
A strip of zinc is added to a solution of 6.0-molar hydrobromic acid
Group I with water video

46. 2007 Question

48. Cation Replacement Reaction of Zinc and Tin (II) Chloride
Website:
Zinc(s) + Tin (II) Chloride(aq)  Tin(s) + Zinc (II) Chloride(aq)
Zn(s) + SnCl2(aq)  Sn(s) + ZnCl2(aq)

49. Thermite Reaction 2Al(s) + Fe2O3 (s)  Al2O3 (s) + 2Fe(l)

50. A solution of copper (II) sulfate is spilled onto a sheet of freshly polished aluminum metal.
Bar of strontium metal is immersed in a 1.0 M copper (II) nitrate solution.
A piece of copper wire is placed in a solution of silver nitrate
A small piece of calcium metal is added to hot distilled water
A solution of tin (II) nitrate is added to a solution of silver nitrate

51. A mixture of powdered iron (III) oxide and powdered aluminum metal is heat strongly.
A bar of zinc metal is immersed in a solution of copper (II) sulfate
A piece of nickel metal is immersed in a solution of copper (II) sulfate
Solutions of tin (II) chloride and iron (III) chloride are mixed

52. Cu+2 (aq) + Fe(s)  Cu(s) + Fe+2 Cu+2 (aq) + Zn(s)  Cu(s) + Zn+2
Growing Crystals in Gels are a great activity you can use to demonstrate single replacement reactions.
Solutions:
1. Saturated Sodium metasilicate- Flinn Scientific (CAT No. S0102) – Needs to be diluted to a density of 1.06 g/ml. About 158 ml of the commercial solution diluted to one liter of solution will yield a proper density.
2. Commercial White Vinegar
M CuCl2 (13.5g/100ml H2O)
M Pb(NO3)2 (33.1g/100ml H2O)

53. Pb+2(aq) + Zn(s)  Zn+2(aq) + Pb(s)

54. Anion Replacement
In the second, a halogen replaces another halogen as the negative ion.
N20 + A+B A+N- + B20
Chlorine gas is bubbled through a solution of potassium bromide
Liquid bromine is shaken with 0.5M sodium iodide solution
Chlorine gas is bubbled into a solution of sodium bromide

56. Halogen Replacement

57. To prepare a saturated solution of aqueous bromine, mix equal volumes of 1.28 M NaBr, 1.28 M HCl, and household bleach. Prepare only as much solution as you need to the activity in working fume hood to avoid unnecessary exposure to bromine vapor. There is no need to store the bromine water since it is easily prepared. It may also be helpful to mix the solutions in a clear glass bottle allowing your students to view the color of elemental bromine.
Discussion:
Since the solubility of bromine in water at 25EC is moles/liter , a saturated aqueous bromine solution can easily be prepared as needed by mixing equal volumes of a 1.28 M sodium or potassium bromide solution, a 1.28 M hydrochloric acid solution, and common household bleach. The three reagents react according to the equation:
The reaction between bleach and hydrochloric acid produces elemental chlorine which then will replace the bromine in sodium bromide producing bromine and sodium chloride.
A saturated solution of aqueous chlorine can be prepared in the same fashion. To prepare 100 ml a saturated aqueous solution of chlorine, mix 1.5 ml of concentrated HCl with 13 ml of bleach in 84 ml of water. The solubility of chlorine at 25EC is M (2)

58. 2007 Question

59. Special Red-ox Reactions
Hydrogen reacts with hot metallic oxide to produce the elemental metal and water
Hydrogen gas is passed over hot iron(II) oxide powder
Oxygen react with Metal Sulfides to produce Metallic Oxides and Sulfur Dioxide

60. Copper reacts with Concentrated Sulfuric Acid
Copper Reacts with Concentrated Nitric Acid

63. Typical Reactions

64. Oxidation States of Manganese
Procedure
Place 10 ml of a Water into Four Graduated Cylinders
Place one tablet #1 into each Cylinder
.01 M KMnO4 solution is in four small cylinders labeled A , B, N ( Place Tablet 1/10 ml water)
To Flask A, Add 10 ml of 3M H2SO4
MnO H+
To Flask B, add 10 ml of 5 M NaOH.
MnO OH-
To Flask N add nothing.
MnO4-

65. To Flask A add .01M NaHSO3 ( Tablet 2) slowly till you get a colorless Mn2+ ion.
MnO H++ HSO3- 3H2O + 2Mn2+ + 5SO42-
To Flask N add .01M NaHSO3 ( Tablet 2)until a brown precipitate forms.
2MnO HSO SO H++ H2O +MnO2
To Flask B slowly add .01M NaHSO3 ( Tablet 2) until a green solution forms.
2MnO4- + OH-+ HSO MnO H2O + SO42-

66. Sulfite ion is readily oxidized to sulfate
Sulfite ion is readily oxidized to sulfate. On prolonged exposure to air, this oxidation occurs with atmospheric oxygen:
2SO32-(aq) + O2(g) --> 2SO42-(aq)
Sulfite or sulfur dioxide will decolorize permanganate. This de-colorization serves as a convenient test for sulfur dioxide:
2MnO4-(aq) + 5SO2(g) + 2H2O(l) --> 5SO42-(aq) + 2Mn2+(aq) + 4H+(aq)

67. 2007 Question

69. ) Formation of a Silver Mirror
Website:
: Preparing Oxygen from Bleach
Website:

70. An acidic solution of potassium dichromate is added to a solution of iron (II) nitrate.
Acidified solutions of potassium permanganate and iron (II) nitrate are mixed together
Solution of iron (II) chloride is added to an acidified solution of sodium dichromate
A concentrated solution of hydrochloric acid is added to solid potassium permanganate.

71. A solution of potassium dichromate is added to an acidified solution of iron(II) chloride.
A concentrated solution of hydrochloric acid is added to solid potassium permanganate.
Solutions of potassium permanganate and sodium oxalate are mixed.
A solution of sodium bromide is added to an acidified solution of potassium bromate

72. Reactions Driven by Solubility and Precipitation
Formation of Gases ( Increase in entropy)
Formation of Water
Coordinate Covalent Bond Formation ( Lewis Acid-Base)
Formation Constants

73. Formation of Water Metal Oxide + an Acid Salt + Water
Metal Hydroxide + an Acid Salt + Water
(a special type of reaction called neutralization)
A 0.1 M nitrous acid solution is added to the same volume of a 0.1 M sodium hydroxide solution
A 0.02 M hydrochloric acid solution is mixed with an equal volume of a 0.01 M calcium hydroxide solution.

74. Lewis Acid-Base Reactions (Coordinate Covalent Bond Formation)
Ammonia gas is mixed with hydrogen chloride gas.
Methylamine gas is bubbled into distilled water
phosphine (phosphorus trihydride) gas is bubbled into liquid boron trichloride

75. Formation of Gas and Water
Metal Carbonate + an Acid Salt + Carbon Dioxide + Water
Hydrogen iodide gas is bubbled into a solution of lithium carbonate
Solid zinc carbonate is added to 1.0 M sulfuric acid.
Carbon dioxide and Water- Carbon Dioxide is easily produced by the reaction of sodium bicarbonate and vinegar.

76. 2007 Question

77. Metal hydrides + Water Metal Hydroxide + Hydrogen Gas
Solid calcium hydride is added to distilled water
Solid sodium hydride is added to water

78. Metal Bicarbonate (Hydrogen Carbonate) +
Metal Bicarbonate (Hydrogen Carbonate) + an Acid Salt + Carbon Dioxide + Water
Excess hydrobromic acid solution is added to a solution of potassium hydrogen carbonate.

79. PREDICTIONS BASED ON SOLUBILITY
If one or both of the products in the double replacement reaction is insoluble in water, the reaction will occur.

80. SOLUBILITY RULES FOR COMMON IONIC COMPOUNDS IN WATER
1. All nitrates, chlorates, and acetates are soluble in water. Silver acetate is sparingly soluble.
2. Most common acids are soluble in water.
3. All common IA, and ammonium compounds are soluble in water.
4. All chlorides, bromides, and iodides are soluble in water except silver, mercury (I), and lead. HgI2 and HgBr2 are insoluble in water.
5. All sulfates are soluble in water except CaSO4, SrSO4, BaSO4, PbSO4, Hg2SO4. Ag2SO4 is sparingly soluble in water.
6. All carbonates, phosphates, oxides, and sulfites are insoluble in water but soluble in dilute acids except the IA and ammonium compounds.
7. The sulfides of all metals are insoluble in water except the IA, IIA, and ammonium sulfides.
8. All hydroxides are insoluble in water except the IA, Ca(OH)2, Sr(OH)2, and Ba(OH)2 hydroxides.

83. Nonmetal Oxide and Metal Hydroxide
) Reaction of Carbon Dioxide and Limewater
Website:
CO2(g) + Ca(OH)2(aq)  CaCO3(s) + H2O(l)

84. A solution of sodium phosphate is added to a solution of aluminum nitrate
A solution of potassium phosphate is mixed with a solution of calcium acetate
A solution of sodium Iodide is added to a solution of lead (II) acetate
A solution of lead(II) nitrate is added to a solution of potassium sulfate.

85. 2007 Question

86. Complex Ion Formation
Often an ion in water solution is in a more complex species, in which the ion is bound to several water molecules
A complex ion consists of a central ion to which are bonded two, four, or six neutral or ionic species called ligands
AMPHOTERIC
Lead and Zinc form complexes with hydroxide
The hydroxides of lead and zinc are soluble in both acidic and basic solutions
Hydroxides that have this property are called amphoteric

87. Halide complexes Ammonia complexes
Al F-  < > [AlF6]3-
2.5 x 104
Al F-  < >  [AlF4]-1
2.0 x 108
 Be F-  < >  [BeF4]2-
1.3 x 1013
Sn F-  < >  [SnF6]2-
1.0 x 1025
Cu+ + 2 Cl-  < >  [CuCl2]-1
3.0 x 105
Ag+ + 2 Cl-  < >  [AgCl2]-1
1.8 x 105
Pb Cl-  < >  [PbCl4]2-
2.5 x 1015
Zn Cl-  < >  [ZnCl4]2-
1.6 
Hg Cl-  < >  [HgCl4]2-
5.0 x 1015
Cu+ + 2 Br-  < >  [CuBr2]-1
8.0 x 105
Ag+ + 2 Br-  < >  [AgBr2]-1
1.0 x 1011
Ammonia complexes
Ag+ + 2 NH3  < >    [Ag(NH3)2]+
1.6 x 107
Zn NH3  < >   [Zn(NH3)4]2+
7.8 x 108
Cu NH3  < >  [Cu(NH3)4]2+
1.1 x 1013
Hg NH3  < >  [Hg(NH3)4]2+
1.8 x 1019
Co NH3  < >  [Co(NH3)6]2+
5.0 x 104
Co NH3  < >  [Co(NH3)6]3+
4.6 x 1033
Cd NH3  < >  [Cd(NH3)6]2+
2.6 x 105
Ni NH3  < >   [Ni(NH3)6]2+

88. Complexes with other monodentate ligands
Cyanide complexes
Fe CN-  < >  [Fe(CN)6]4-
1.0 x 1024
Fe CN-  < >  [Fe(CN)6]3-
1.0 x 1031
Ag+ + 2 CN-  < >  [Ag(CN)2]-1
5.3 x 1018
Cu+ + 2 CN-  < >  [Cu(CN)2]-1
1.0 x 1016
Cd CN-  < >  [Cd(CN)4]2-
7.7 x 1016
Au+ + 2 CN-  < >  [Au(CN)2]-1
2.0 x 1038
Complexes with other monodentate ligands
Ag+ + 2 CH3NH2  < >  [Ag(CH3NH2)2]+1
7.8 x 106
Cd SCN-  < >  [Cd(SCN)4]2-
1.0 x 103
Cu2+ 2 SCN-  < >  [Cu(SCN)2] 
5.6 x 103
Fe3+ 3 SCN-  < >  [Fe(SCN)3]
2.0 x 106
Hg2+ 4 SCN-  < >  [Hg(SCN)4]2-
5.0 x 1021
Cu2+ 4 OH-  < >  [Cu(OH)4]2-
1.3 x 1016
Zn2+ 4 OH-  < >  [Zn(OH)4]2-
2.0 x 1020

89. Excess concentrated aqueous ammonia is added to a solution of nickel (II) bromide
Excess concentrated hydrochloric acid is added to a 1.0 M solution of cobalt (II) chloride
A drop of potassium thiocyanate solution is added to a solution of iron (III) nitrate.
Excess concentrated ammonia solution is added to a solution of nickel (II) sulfate
Excess sodium cyanide solution is added to a solution of silver nitrate

90. Balancing Red-Ox Reactions

91. Red-Ox Continued

92. Red-Ox Under Basic Conditions

93. Red-Ox continued

94. Organic Where in The Curriculum? Thermochemistry Stoichiometry
Bonding and Molecular Structure