Download double-replacement reaction

Exam 3
• Objectives:
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Nomenclature m-nm, m(VOS)-nm, nm-nm
Evidence for Chemical Reactions
Writing Chemical Equations
Balancing Chemical Equations
Classifying Chemical Reactions
Combination Reactions
Decomposition Reactions
Single-Replacement Reactions The Activity Series
Double-Replacement Reactions Solubility Rules
Neutralization Reactions H+ + OH-  H2O(l)
Nomenclature
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Evidence for a chemical Reactions
• There are four ways to tell if a chemical
reaction has occurred:
1. A gas is produced.
2. An insoluble solid is produced.
3. A permanent color change is observed.
4. An energy change is observed.
• An exothermic reaction gives off heat and
an endothermic reaction absorbs heat.
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Diatomic Molecules
• Seven nonmetals occur naturally as
diatomic molecules:
1.
2.
3.
4.
5.
6.
7.
Hydrogen (H2)
Nitrogen (N2)
Oxygen (O2)
Halogen (F2)
Halogen (Cl2)
Halogen (Br2)
Halogen (I2)
• These elements are written as diatomic molecules when they
appear in chemical reactions.
H2(g) N2 (g) F2(g) O2(g) I2(s) Cl2(g) Br2(l)
Have No Fear Of Ice Cold Beer‖
Solid – (s)  Fe(s)
Liquid – (l)  H2O(l)
Gas – (g)  CO2(g)
Aqueous – (aq)  NaCl(aq)
Aqueous means “dissolved in water”
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A Chemical Reaction
reacts with, added to
produces, yields, gives
A(s) + B (aq)  C (l) + D(g) + E(aq)
solid
aqueous
liquid
gas
Balancing Chemical Eqs
• When we balance a chemical equation, the
number of each type of atom must be the
same on both the product and reactant sides
of the equation.
• We use coefficients in front of compounds
to balance chemical reactions. Never change
the subscripts
P + I2 
PI3
P + 3/2 I2 
PI3
x2
2P + 3 I2  2 PI3
2P
6I
2P
6I
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Practice: Balancing Chemical Eqs
Classifying Chemical Reactions
• We can place chemical reactions into five
categories:
Synthesis rxs
Decomposition rxs
Oxidation–Reduction rxs
A + BC  B + AC
Precipitation rxs
Acid-base rxs
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Combination Reactions
• A combination reaction is a reaction in
which simpler substances are combined into
a more complex compound.
• Combination reactions are also called
synthesis reactions.
• We will look at two combination reactions:
1. The reaction of a metal with nonmetal
2. The reaction of a nonmetal with nonmetal
Reactions of Metals with Oxygen
• When a metal is heated with oxygen gas, a
metal oxide is produced.
metal + oxygen gas → metal oxide
• For example, magnesium metal produces
magnesium oxide.
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Reactions of Nonmetals with Oxygen
• Oxygen and a nonmetal react to produce a
nonmetal oxide.
nonmetal + oxygen gas → nonmetal oxide
• Sulfur reacts with oxygen to
produce sulfur dioxide gas.
∆
S(s) + O2(g) → SO2(g)
Metal and Nonmetal Reactions
• A metal and a nonmetal react in a combination
reaction to give an ionic compound.
metal + nonmetal → ionic compound
• Lithium reacts with bromine gas to produce
lithium bromide.
∆
2 Li(s) + Br2(g) → 2 LiBr(s)
• When a main group (group I & II) metal reacts
with a nonmetal, the formula of the ionic
compound is predictable. If the compound
contains a transition metal, the formula is not
predictable.
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Decomposition Reactions
•
Occurs when a compound is broken down into
simpler substances.
• Ex: Electrolysis of water
 2H2O(l)  2H2(g) + O2(g)
E=+1.23v
Ex: Carbonates will decompose
when heated
Combination/decomposition summary
• In combination reactions, two or more
smaller molecules are combined into a more
complex molecule.
• In a decomposition reaction, a molecule
breaks apart into two or more simpler
molecules.
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Single-Replacement Reactions
• A single-replacement reaction is a reaction in
which a more active metal displaces another
less active metal in a compound.
• If a metal precedes another in the
activity series, it will undergo a
single-replacement reaction.
A + BC  B + AC
Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s)
Double-Replacement Reactions
• In a double-replacement reaction, two
ionic compounds in aqueous solution switch
anions and produce an insoluble substance.
AX + BZ → AZ + BX
• If either AZ or BX is an insoluble
compound, a precipitate will appear and
there is a chemical reaction.
• If no precipitate is formed, there is no
reaction.
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Neutralization Reactions
• A neutralization reaction is the reaction of an
acid and a base.
HX + BOH → BX + HOH
• A neutralization reaction produces a salt and
water.
H2SO4(aq) + 2 KOH(aq) → K2SO4(aq) + 2 H2O(l)
Classify the following Reactions
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Predicting whether a reaction will occur
In a single-replacement reaction, a more
active metal displaces a less active metal
according to the activity series.
• In a double-replacement reaction, two
aqueous solutions produce a precipitate of
an insoluble compound.
• The insoluble compound can be predicted
based on the solubility rules.
Single-Replacement: Activity Series
More active will react!
Li > K > Ba > Sr > Ca > Na > Mg > Al > Mn > Zn > Fe > Cd > Co >
Ni > Sn > Pb > (H) > Cu > Ag > Hg > Au
Mg > Cd so it WILL react!
Mg(s) + CdCl2(aq)
 MgCl2(aq) + Cd (s)
The MORE active metal wants to be in a compound!!
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Double-Replacement Reactions, Continued
• Aqueous barium chloride reacts with aqueous
potassium chromate as follows:
BaCl2(aq) + K2CrO4(aq) → BaCrO4(s) + 2 KCl(aq)
From the solubility rules, BaCrO4 is insoluble, so there is a
double-replacement reaction.
• Aqueous sodium chloride reacts with
aqueous lithium nitrate as follows:
NaCl(aq) + LiNO3(aq) → NaNO3(aq) + LiCl(aq)
Both NaNO3 and LiCl are soluble, so there is no reaction.
Practice problems
• Write M.E., C.I.E., and N.I.E. for each of the following
reactions.
• 1) potassium phosphate with copper (II) acetate 
•
• 2) sodium sulfide with iron (III) nitrate 
•
• 3) cesium hydroxide and oxalic acid 
•
• 4) nickel (III) chloride and lead (II) nitrate 
•
• 5) chromium (II) bromide with lithium oxalate 
•
• 6) sulfuric acid with rubidium hydroxide 
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Practice problems
• Write M.E., C.I.E., and N.I.E. for each of the following
reactions.
• 7) barium hydroxide with perchloric acid 
•
• 8) cesium chromate with rubidium oxide 
•
• 9) sodium fluoride with nickel (III) sulfate 
•
• 10) antimony (V) carbonate reacts with sulfuric acid to form
antimony (V) sulfate, carbon dioxide, and water
•
• 11) acetic acid with zinc hydroxide 
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