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Bell Ringer
Balance the following equation and indicate whether it is a combination, decomposition, or combustion reaction:
C3H6(g) + O2(g)CO2(g) + H2O(g)
2C3H6(g) + 9O2(g)6CO2(g) + 6H2O(g)
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2. Types of Chemical Reactions
Precipitation: a solid ionic substance forms from the mixture of two solutions of ionic substances.
Acid–base: reactions that involve the transfer of a proton (H+) between reactants.
Oxidation–reduction: reactions that involve the transfer of electrons between reactants.
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3. AgNO3 (aq) + KCl (aq)  AgCl (s) + KNO3 (aq)
A precipitate is an insoluble solid compound formed during a chemical reaction in solution.
Predicting Precipitation Reactions
1. Predict the products (exchange of parts).
2. Determine the state of each product: (s), (l), (g), (aq).
If all products are aqueous (aq), no net reaction occurred.
AgNO3 (aq) + KCl (aq)  AgCl (s) + KNO3 (aq)
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5. Sample Exercise
Classify the following ionic compounds as soluble or insoluble in water:
a) sodium carbonate (Na2CO3)
b) lead sulfate (PbSO4)
c) cobalt (II) hydroxide
d) barium nitrate
e) ammonium phosphate
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6. Sample Exercise
Predict the identity of the precipitate that forms when solutions of BaCl2 and K2SO4 are mixed.
Write the balanced chemical equation for the reaction.
c) What compound precipitates when solutions of Fe2(SO4)3 and LiOH are mixed?
d) Write a balanced equation for the reaction.
e) Will a precipitate form when solutions of Ba(NO3)2 and KOH are mixed?
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7. Arrhenius Acid Arrhenius Base
A substance that produces hydrogen ions, H+, when it dissolves in water.
Arrhenius Base
A substance that produces hydroxide ions, OH−, when it dissolves in water.
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8. Acids There are only seven strong acids: Hydrochloric (HCl)
Hydrobromic (HBr)
Hydroiodic (HI)
Nitric (HNO3)
Sulfuric (H2SO4)
Chloric (HClO3)
Perchloric (HClO4)
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9. Bases The strong bases are the soluble metal salts of hydroxide ion:
Alkali metals
Calcium
Strontium
Barium

10. Neutralization Reaction
A reaction of an acid and a base that results in an ionic compound (a salt) and possibly water.
Acid−base reactions with gas−formation
Sulfides, carbonates, sulfites react with acid to form a gas.
Na2S(aq) + 2HCl(aq)  2NaCl(aq) + H2S(g)
Na2CO3(aq) + 2HCl(aq)  2NaCl(aq) + H2O(l) + CO2(g)
Na2SO3(aq) + 2HCl(aq)  2NaCl(aq) + H2O(l) + SO2(g)
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11. Oxidation-Reduction Reactions
An oxidation occurs when an atom or ion loses electrons.
A reduction occurs when an atom or ion gains electrons.
One cannot occur without the other.
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Oxidation Numbers
To determine if an oxidation–reduction reaction has occurred, we assign an oxidation number to each element in a neutral compound or charged entity.
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13. Rules for Assigning Oxidation Numbers
Elements: The oxidation number of an atom in an element is zero.
Monatomic ions: The oxidation number of an atom in a monatomic ion equals the charge on the ion.
Oxygen: The oxidation number of oxygen is −2 in most of its compounds. (An exception is O in H2O2 and other peroxides, where the oxidation number is −1.)
Hydrogen: The oxidation number of hydrogen is +1 in most of its compounds. (The oxidation number of hydrogen is −1 in binary compounds with a metal such as CaH2.)
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14. Halogens: The oxidation number of fluorine is −1
Halogens: The oxidation number of fluorine is −1. Each of the other halogens (Cl, Br, I) has an oxidation number of −1 in binary compounds, except when the other element is another halogen above it in the periodic table or the other element is oxygen.
Compounds and ions: The sum of the oxidation numbers of the atoms in a compound is zero. The sum of the oxidation numbers of the atoms in a polyatomic ion equals the charge on the ion.
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15. What is the oxidation number of Cr in dichromate, Cr2O72−?
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16. Displacement Reactions
In displacement reactions, ions oxidize an element.
The ions, then, are reduced.
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17. Displacement Reactions
In this reaction,
silver ions oxidize
copper metal:
Cu(s) + 2Ag+(aq)  Cu2+(aq) + 2Ag(s)
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18. Displacement Reactions
The reverse reaction,
however, does not
occur:
Cu2+(aq) + 2Ag(s)  Cu(s) + 2Ag+(aq) x
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19. © 2012 Pearson Education, Inc.
Activity Series
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20. Exercise Determining When an Oxidation-Reduction Reaction Can Occur
Will an aqueous solution of iron(II) chloride oxidize magnesium metal? If so, write the balanced molecular and net ionic equations for the reaction. 20

21. Ag+(aq) + Cl–(aq) AgCl(s)
Exercise Determining the Quantity of Solute by Titration
The quantity of Cl– in a municipal water supply is determined by titrating the sample with Ag+. The precipitation reaction taking place during the titration is
Ag+(aq) + Cl–(aq) AgCl(s)
The end point in this type of titration is marked by a change in color of a special type of indicator. (a) How many grams of chloride ion are in a sample of the water if 20.2 mL of M Ag+ is needed to react with all the chloride in the sample? (b) If the sample has a mass of 10.0 g, what percent Cl– does it contain? 21