Download T10 Types of reactions

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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Types of Chemical Reactions
1. Precipitation: a solid ionic substance
forms from the mixture of two solutions of
ionic substances.
2. Acid–base: reactions that involve the
transfer of a proton (H+) between
reactants.
3. Oxidation–reduction: reactions that
involve the transfer of electrons between
reactants.
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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).
3. If all products are aqueous (aq), no net
reaction occurred.
AgNO3 (aq) + KCl (aq)  AgCl (s) + KNO3 (aq)
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© 2009, Prentice-Hall,
Sample Exercise
Classify the following ionic compounds as
soluble or insoluble in water:
a)
b)
c)
d)
e)
sodium carbonate (Na2CO3)
lead sulfate (PbSO4)
cobalt (II) hydroxide
barium nitrate
ammonium phosphate
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Sample Exercise
a) Predict the identity of the precipitate that forms
when solutions of BaCl2 and K2SO4 are mixed.
b) 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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Arrhenius Acid
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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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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Bases
The strong bases are
the soluble metal
salts of hydroxide ion:
•
•
•
•
Alkali metals
Calcium
Strontium
Barium
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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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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Rules for Assigning Oxidation Numbers
1. Elements: The oxidation number of an atom in an
element is zero.
2. Monatomic ions: The oxidation number of an atom
in a monatomic ion equals the charge on the ion.
3. 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.)
4. 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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5. 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.
6. 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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What is the oxidation number of Cr in
dichromate, Cr2O72−?
Cr
O
2(oxidation number of Cr) + 7(−2) = −2
2(oxidation number of Cr) + (−14) = −2
2(oxidation number of Cr) = +12
Oxidation number of Cr = +6
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Displacement Reactions
• In displacement reactions, ions oxidize an element.
• The ions, then, are reduced.
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Displacement Reactions
In this reaction,
silver ions oxidize
copper metal:
Cu(s) + 2Ag+(aq)  Cu2+(aq) + 2Ag(s)
© 2012 Pearson Education, Inc.
Displacement Reactions
The reverse reaction,
however, does not
occur:
x Cu(s) + 2Ag+(aq)
Cu2+(aq) + 2Ag(s) 
© 2012 Pearson Education, Inc.
Activity Series
© 2012 Pearson Education, Inc.
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.
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 0.100 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?