Transcript Predicting Reactions

Predicting Reactions
Presented by
Mr. Mark Langella
AP Chemistry Instructor
College Board Consultant
Why do the reactions occur?
 Gibbs
Free Energy drives the
Spontaneous reactions
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Lower PE energy
Formation of Stronger Bonds
Greater Entropy ( Formation of Gases)
 Solubility
 Formation
Constant
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
 Formula
equations
 Formula equations consist of formulas
substituted for the names in the word
equation. The reaction above becomes
 C + O2
CO2

Ionic equations
 In ionic equations, all water soluble compounds
in an aqueous solution are separated into ions.
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2NaI(aq) + Pb(NO3)2(aq)
2NaNO3(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.
 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)
PbI2(s)
 Pb2+(aq) + 2I-(aq)
PbI2(s)

2Na+(aq) + 2NO3-(aq) +
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.
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.
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?
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.
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.
Metal + Nonmetal
 Magnesium
 A strip
Salt
ribbon is burned in oxygen
of magnesium metal is heated
strongly in pure nitrogen gas
Online Demos
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Reaction of Magnesium and Oxygen
http://boyles.sdsmt.edu/magburn/magnesium_burning.htm
Reaction of Iron and Sulfur
http://www.pc.chemie.uni-siegen.de/pci/versuche/english/v21-1.html
Reaction of Potassium and Oxygen
http://neon.chem.ox.ac.uk/vrchemistry/FilmStudio/alkalimetals/HTML/pag
e08.htm
Reaction of Lithium and Oxygen
http://neon.chem.ox.ac.uk/vrchemistry/FilmStudio/alkalimetals/HTML/pag
e02.htm
Reaction of Lithium and Chlorine
http://neon.chem.ox.ac.uk/vrchemistry/FilmStudio/alkalimetals/HTML/pag
e04.htm
Reaction of Sodium and Oxygen
http://neon.chem.ox.ac.uk/vrchemistry/FilmStudio/alkalimetals/HTML/pag
e05.htm
Reaction of Zinc and Sulfur
http://boyles.sdsmt.edu/znsulf/zincsul.htm
Nonmetal + Nonmetal Molecular
compounds
 Pure
Solid Phosphorus (White Form) is
burned in air
 Reaction
of Phosphorus and Chlorine

Website:
http://boyles.sdsmt.edu/pwithcl/reaction_of
_white_phosphorus_and.htm
Reaction of Hydrogen and
Oxygen
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)
2LiH
Nonmetal Oxide + Water
 Oxy Acid=
Oxyacid
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
 Phosphorus(V)
oxide powder is sprinkled
over distilled water
 Sulfur
water
dioxide gas is bubbled into distilled
Metal oxide + water
metal hydroxide
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Solid Cesium Oxide is added to water
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Solid sodium oxide is added to distilled water
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Powdered strontium oxide is added to distilled
water
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Calcium oxide powder is added to distilled water
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Solid barium oxide is added to distilled water
Demo
Cmd
Na2O
MgO
Al3O2
SiO2
P4O10
SO3
Cl2O7
%Ionic
79
68
56
45
32
17
2
Solid
Ionic
Ionic
Ionic
Network
Molecular
Molecular
Molecular
Hydroxide
Formula
NaOH
Mg(OH)2
Al(OH)3
Si(OH)4
OP(OH)3
O2S(OH)2
O3Cl(OH)
SiO2+2H2O
H3PO4
H2SO4
HClO3
Slightly
acidic
Acidic
Stronger
Acid
Very Acidic
Formula
Very
Basic
Basic
Ampho.
Hydrogen-Nonmetal + Water
 Hydrogen
Acidic Solution
Chloride gas bubbled into water
Metal oxide + nonmetal oxide
metal ion attached to common
polyatomic ion
 Metal
oxide + carbon dioxide
carbonate
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metal
Carbon dioxide gas is passed over hot, solid
sodium oxide
 Metal
oxide + sulfur dioxide
Metal
sulfite
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Sulfur Dioxide is passed over solid calcium oxide
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
Decomposition of Metal Carbonate
 Heating
a metal carbonate always yields
the metal oxide and carbon dioxide.
 MCO3
MO + CO2
 Powdered magnesium carbonate is
heated strongly
 Solid calcium carbonate is strongly heated
Metal Hydrogen Carbonate
Decomposition
 Heating
a metal bicarbonate gives the
metal oxide, carbon dioxide, and water.
 MHCO3
MO + H2O + CO2
 http://www.chemguide.co.uk/inorganic/gro
up1/compounds.html
 Solid
Sodium Hydrogen Carbonate is
strongly heated
Heating the nitrates
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Most nitrates tend to decompose on heating to give the metal oxide,
brown fumes of nitrogen dioxide, and oxygen.
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For example, a typical Group 2 nitrate like magnesium nitrate
decomposes like this:
2 Mg(NO3)2 =
2 MgO + 2 NO2 + 3 O2
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In Group 1, lithium nitrate behaves in the same way - producing
lithium oxide, nitrogen dioxide and oxygen.
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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.
Decomposition of Metal Hydroxides
 Heating
a metal hydroxide gives the metal
oxide and water
 MOH
MO + H2O
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
Metal Chlorate Decomposition
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Heating a metal chlorate gives the metal
chloride plus oxygen.
 MClO3
MCl + O2
Electrolysis of Binary Compound
 Electrolysis
of a molten salt (ionic
compound) separates the substance into
its elements.
 MN
M+N
Ammonium Compound
Decomposition
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Ammonium
Carbonates
 Solid ammonium
carbonate is heated
(NH4)2CO3
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=
2NH3 + 2CO2 + H2O
Ammonium Hydroxide
NH4OH  NH3+ H2O
2007 Questions
(NH4)2CO3
=
2NH3 + 2CO2 + H2O
Peroxide Decomposition
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Elephant’s Toothpaste
Website:
http://boyles.sdsmt.edu/tp
aste/elephants.htm
Genie in a Bottle Demo
Website:
http://boyles.sdsmt.edu/g
eniebot/genie.htm
Reactions Based on Reduction Potentials
EMF Potential
 Reduction

and Oxidation
Single replacement
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
Replacement of Hydrogen
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Reaction of Magnesium and Different Concentrations of Acids
Website: http://boyles.sdsmt.edu/kinetic/mercadokinetics.htm
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:
http://boyles.sdsmt.edu/sodwat/reaction_of_sodium_and_water.htm
Sodium(s) + Water(l)  Sodium Hydroxide(aq) + Hydrogen(g)
2Na(s) + 2H2O(l)  2NaOH(aq) + H2(g)
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) Reaction of Potassium and Water
Website: http://www.chem.shef.ac.uk/webelementsmoov/K_H2O.mov
Potassium(s) + Water(l)  Potassium Hydroxide(aq) + Hydrogen(g)
2K(s) + 2H2O  2KOH + H2(g)
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A strip of zinc is added to a solution of 6.0-molar hydrobromic acid
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Group I with water video
http://video.google.com/videoplay?docid=2134266654801392897&q=rubidium+water
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2007 Question
Cation Replacement
 Reaction
of Zinc and Tin (II) Chloride
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Website:
http://www.chemtopics.com/lectures/unit02
/lecture1/displace.htm
 Zinc(s) + Tin (II) Chloride(aq)  Tin(s) +
Zinc (II) Chloride(aq)
 Zn(s) + SnCl2(aq)  Sn(s) + ZnCl2(aq)
Thermite Reaction
 2Al(s)
+ Fe2O3 (s)  Al2O3 (s) + 2Fe(l)
 http://boyles.sdsmt.edu/thermite/therm.htm
 http://www2.chemie.uni-
erlangen.de/education/medprak/videos/the
rmit_v.mpg
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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
 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
Cu+2 (aq) + Fe(s)  Cu(s) + Fe+2
Cu+2 (aq) + Zn(s)  Cu(s) + Zn+2
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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
3.
1.0 M CuCl2 (13.5g/100ml
H2O)
4.
1.0 M Pb(NO3)2
(33.1g/100ml H2O)
Pb+2(aq) + Zn(s)  Zn+2(aq) + Pb(s)
Anion Replacement
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In the second, a halogen replaces another
halogen as the negative ion.
 N20 + A+BA+N- + B20
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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
Halogen Replacement
NaClO(aq)  2HCl(aq)  Cl (aq)  NaCl(aq)  H O( )
2
2
Cl (g)  2NaBr(aq)  2NaCl(aq)  Br (aq)
2
2
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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.
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Discussion:
Since the solubility of bromine in water at 25EC is 0.214 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:
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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 0.092
M (2)
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2007 Question
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
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Copper reacts with
Concentrated Sulfuric
Acid
Cu + 2 H2SO4  CuSO4+SO2+2 H2O
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Copper Reacts with
Concentrated Nitric
Acid
3Cu + 8HNO3  Cu(NO3)2+ NO + 4H2O
Typical Reactions
Oxidation States of Manganese
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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
MnO4- + H+
To Flask B, add 10 ml of 5 M NaOH.
MnO4- + OHTo Flask N add nothing.
MnO4-
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To Flask A add .01M NaHSO3 ( Tablet 2) slowly
till you get a colorless Mn2+ ion.
MnO4- + 5H++ HSO3- 3H2O + 2Mn2+ + 5SO42To Flask N add .01M NaHSO3 ( Tablet 2)until a
brown precipitate forms.
2MnO4- + 3HSO33SO42- + H++ H2O +MnO2
To Flask B slowly add .01M NaHSO3 ( Tablet 2)
until a green solution forms.
2MnO4- + OH-+ HSO32MnO42- + 2H2O +
SO42-
 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)
2007 Question
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Formation of a Silver Mirror
 Website:
http://boyles.sdsmt.edu/agmirror/agmir.htm
 : Preparing Oxygen from Bleach
 Website:
http://boyles.sdsmt.edu/prepoxyg/preparati
on_of_oxygen_gas_from_b.htm
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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.
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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
Reactions Driven by
 Solubility
and Precipitation
 Formation of Gases ( Increase in entropy)
 Formation of Water
 Coordinate Covalent Bond Formation
( Lewis Acid-Base)
 Formation Constants
Formation of Water
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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.
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
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.
2007 Question
Metal hydrides + Water Metal
Hydroxide + Hydrogen Gas
 Solid
calcium hydride is added to distilled
water
 Solid
sodium hydride is added to water
 Metal
Bicarbonate (Hydrogen Carbonate)
+ an Acid
Salt + Carbon Dioxide +
Water
 Excess hydrobromic acid solution is added
to a solution of potassium hydrogen
carbonate.
PREDICTIONS BASED ON
SOLUBILITY
 If
one or both of the products in the double
replacement reaction is insoluble in
water, the reaction will occur.
SOLUBILITY RULES FOR COMMON IONIC
COMPOUNDS IN WATER
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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.
Nonmetal Oxide and Metal
Hydroxide
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Reaction of Carbon Dioxide and
Limewater
 Website:
http://boyles.sdsmt.edu/respira/respir.htm
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CO2(g) + Ca(OH)2(aq)  CaCO3(s) + H2O(l)
 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.
2007 Question
Complex Ion Formation
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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
Halide complexes
Al3+ + 6 F- <----------> [AlF6]3-
2.5 x 104
Al3+ + 4 F- <----------> [AlF4]-1
2.0 x 108
Be2+ + 4 F- <----------> [BeF4]2-
1.3 x 1013
Sn4+ + 6 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
Pb2+ + 4 Cl- <----------> [PbCl4]2-
2.5 x 1015
Zn2+ + 4 Cl- <----------> [ZnCl4]2-
1.6
Hg2+ + 4 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
Zn2+ + 4 NH3 <----------> [Zn(NH3)4]2+
7.8 x 108
Cu2+ + 4 NH3 <----------> [Cu(NH3)4]2+
1.1 x 1013
Hg2+ + 4 NH3 <----------> [Hg(NH3)4]2+
1.8 x 1019
Co2+ + 6 NH3 <----------> [Co(NH3)6]2+
5.0 x 104
Co3+ + 6 NH3 <----------> [Co(NH3)6]3+
4.6 x 1033
Cd2+ + 6 NH3 <----------> [Cd(NH3)6]2+
2.6 x 105
Ni2+ + 6 NH3 <----------> [Ni(NH3)6]2+
2.0 x 108
Cyanide complexes
Fe2+ + 6 CN- <----------> [Fe(CN)6]4-
1.0 x 1024
Fe3+ + 6 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
Cd2+ + 4 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
Cd2+ + 4 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
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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
Balancing Red-Ox Reactions
Red-Ox Continued
Red-Ox Under Basic Conditions
Red-Ox continued
Organic
 Where
in The Curriculum?
 Thermochemistry
 Stoichiometry
 Bonding and Molecular Structure