Predicting Reactions
Presented by
Mr. Mark Langella
STANYS 2006
PWISTA.com
11/7/06
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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
 Lose Yourself in Chemical Reactions Google Video

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

Salt
Magnesium ribbon is burned in oxygen
Combination or Synthesis Reactions
 General form
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A+B
C
In this demonstration

2 Mg +

3 Mg + N2
O2
MgO
Mg3N2
The oxygen and nitrogen occur naturally in
the atmosphere
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O2 is 21% of air
N2 is 78% of air
Energy
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Two types of energy are produced in this
demonstration
energy DHf MgO = -601.83 kJ/mole
(kiloJoules per mole)
 heat
this is said to be the ‘heat of formation’ for MgO
 the negative sign indicates the formation is exothermic

 light
energy
approximately 10% of the energy of combustion occurs
as light in this demonstration
 more light than any other known reaction

Online Demos
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Reaction of Iron and Sulfur
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http://www.pc.chemie.uni-siegen.de/pci/versuche/pics/anim/fes.mpg

Fe + S
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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
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FeS
Nonmetal + Nonmetal
compounds
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Reaction of
Hydrogen and
Oxygen
http://www.chem.uiuc.
edu/clcwebsite/video/
Bal2.mov
Molecular
Rubber tubing
Water bottle
clamped onto
a rinstand
Drying tube
Short piece of
Pyrex glass tubing
inserted into a
one-hole stopper
Volumetric flask
containing
NaOH and Al
Reaction of Phosphorus and Chlorine

http://boyles.sdsmt.edu/pwithcl/DirksTwo.as
x
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P4(s) +
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Oxidation Number Changes
10 Cl2(g)
4 PCl5(s)
Nonmetal Oxide + Water

Oxyacid
Oxy Acid= Contains H+ ions attached to
common Polyatomic ion of Nonmetal
Oxide plus one more oxygen
Formation of Carbonic Acid

Carbon dioxide and Water- Carbon Dioxide is
easily produced by the reaction of sodium
bicarbonate and vinegar.

http://boyles.sdsmt.edu/respira/Alexander
Co2Blue.asx
Reaction of Carbon Dioxide and
Limewater

http://boyles.sdsmt.edu/respira/Alexander
Co2White.asx

CO2(g) + Ca(OH)2(l)  CaCO3(s) + H2O(l)
Metal oxide + water
Egg Fry
metal hydroxide
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
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Heating a metal carbonate always yields the metal oxide and carbon
dioxide.
MCO3
MO + CO2
Heating the carbonates
Most carbonates tend to decompose on heating to give the metal oxide and
carbon dioxde.
For example, a typical Group 2 carbonate like calcium carbonate
decomposes like this:
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In Group 1, lithium carbonate behaves in the same way - producing lithium
oxide and carbon dioxide.
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The rest of the Group 1 carbonates don't decompose at Bunsen
temperatures, although at higher temperatures they will. The decomposition
temperatures again increase as you go down the Group.
Metal Hydrogen Carbonate
Decomposition
Heating a metal bicarbonate gives the
metal oxide, carbon dioxide, and water.
 MHCO3
MO + H2O + CO2
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Solid Sodium Hydrogen Carbonate is
strongly heated
Metal Chlorate Decomposition
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Heating a metal chlorate gives the metal
chloride plus oxygen.
MClO3
MCl + O2
Burning Gummi Bears
http://www.webct.com/service/ViewContent?cont
entID=1249557&communityID=858&categoryID
=1249537&sIndex=0
Logger Pro Analysis
Decomposition of Ammonium
Dichromate

http://boyles.sdsmt.edu/dichrom/Ammoniu
mDichromate.asx
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(NH4)2Cr2O7(s)  Cr2O3(s) + N2(g) +
4H2O(g)
Peroxide Decomposition
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Elephant’s Toothpaste
Website:
http://boyles.sdsmt.edu/tpaste/Cain.asx
Genie in a Bottle Demo
Website:
http://boyles.sdsmt.edu/geniebot/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

Reaction of Sodium and Water
http://boyles.sdsmt.edu/sodwat/SodiumWater.asx
http://www.theodoregray.com/PeriodicTable/Stories
/011.2/Videos/SodiumResearch03.html
http://www.theodoregray.com/PeriodicTable/Stories
/011.2/Videos/SodiumResearch02.html
Sodium(s) + Water(l)  Sodium Hydroxide(aq) +
Hydrogen(g)
 2Na(s) + 2H2O(l)  2NaOH(aq) + H2(g)
Reaction of Potassium and
Water

http://www.chem.shef.ac.uk/webelementsmoov/K_H2O.mov

http://www.theodoregray.com/PeriodicTable/AlkaliBangs/019_K_dog
howls.html
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Potassium(s) + Water(l)  Potassium Hydroxide(aq) +
Hydrogen(g)
2K(s) + 2H2O  2KOH + H2(g)
Group I with water video
http://video.google.com/videoplay?docid=2134266654801392897&q=rubidium+water
Reaction of Zinc and Tin (II)
Chloride
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http://www.chemtopics.com/lectures/unit02/lectur
e1/displace.htm
Zinc(s) + Tin (II) Chloride(aq)  Tin(s) + Zinc (II)
Chloride(aq)
Zn(s) + SnCl2(aq)  Sn(s) + ZnCl2(aq)
Zinc(s) + Hydrochloric Acid(aq)  Zinc (II)
Chloride(aq) + H2(g)
Zn(s) + 2HCl(aq)  ZnCl2(aq) + H2(g)
Aluminum and Copper ( II) Chloride
Thermite Reaction
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2Al(s)+Fe2O3(s)
Al2O3(s)+2Fe(l)
http://boyles.sdsmt.edu/thermite/ThirstrupThermit
eClose.asx
http://www2.chemie.unierlangen.de/education/medprak/videos/thermit_v.
mpg
http://video.google.com/videoplay?docid=7231843493488769585&q=Reactions&hl=en
Aqueous Redox Reactions
Oxidation States of Manganese
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Procedure
Add 30 ml of a .01 M KMnO4 solution to four small flasks
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-
Watch the color changes
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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-
The Amazing Purple Drop
Oil Drop Demo
 I2 + H20
HOI ( aq) + HI ( aq)
 Meanwhile
 I2 + 2e- = 2I-, Eo = 0.54 v
 HCHO + 2H+ + 2e- = CH3OH, Eo = 0.19 v
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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
Metal Oxide + an Acid
Salt + Water
 Metal Hydroxide + an Acid
Salt + Water
 (a special type of reaction called
neutralization)
 Milk of Magnesia Demo
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PREDICTIONS BASED ON
SOLUBILITY
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If one or both of the products in the double replacement
reaction is insoluble in water, the reaction will occur.
Reaction #1
Lead Nitrate and Sodium Chromate
Pb(NO3)2 (aq) + Na2CrO4 (aq)  PbCrO4 (s) +
Na NO3(aq)
Pb 2+ + CrO42-  PbCrO4 (s)
Reaction # 2
Silver Nitrate and Hydrochloric Acid
AgNO3(aq) + HCl(aq)  AgCl (s) + HNO3 (aq)
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.
Combustion
Whoosh Bottle
 Rocket Explosions
 Dynamite Soap Mixtures
 Repeating Exploding Flask
