1
2

A reaction in which aqueous ionic compounds
rearrange cations (A & B) and anions (X & Y),
resulting in the formation of new compounds
A X
+BY 
AY + B
X
3

A reaction that forms a solid

A reaction that forms a gas

A reaction that forms water (neutralization)
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

First determine the ions that make up the
reactants.
For example, consider the reaction between
lithium chloride and lead(II) nitrate:
LiCl(aq) + Pb(NO3)2(aq) 
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
The reactants are composed of four ions:
 LiCl(aq)
+ Pb(NO3)2(aq) 
 Lithium
ions, Li+
 Chloride
ions, Cl-
 Lead(II)
ions, Pb2+
 Nitrate
ions, NO36

To determine the products of the reaction, simply
change the pairs of ions.
2LiCl(aq) + Pb(NO3)2(aq)  2LiNO3(aq) + PbCl2(s)
Lithium chloride +lead(II) nitrate
lithium nitrate + lead(II) chloride
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Specific Example:
MgCl2(aq) + Ca(OH)2(aq)  Mg(OH)2(s) + CaCl2(aq)
What “sign” suggests a chemical
reaction has occurred?
If there is no precipitate formed,
there is NO reaction.
How can we predict precipitate formation?
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1)

2)
3)
When a precipitate is produced from
the reaction of 2 aqueous reactants.
To determine which products are precipitates
(insoluble in water), you must check your
solubility chart
When a pure liquid is formed – typically
water.
When a gas is produced (often CO2, H2,
and O2)
In summary any reaction where the two products
are not aqueous!
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SOLUBILITY





A solution is a homogenous mixture of a solute and a
solvent
Every solute has its own solubility in a given solvent
Solubility is described as the maximum quantity of a
solute that will dissolve in a solvent at a given
temperature and pressure e.g. adding NaCl to water
If a product in a reaction is insoluble a precipitate will
form
We use a SOLUBILITY TABLE to determine whether a
precipitate will form (Nelsons Chemistry 11 p. 137
Table 1)
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11
(a)
(b)
(c)
(d)
(e)
(f)
Ag+
Nitrate
C2H3O2Ba2+
OHPhosphate
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Precipitate Reactions
CaCl2(aq) + Na2CO3(aq) 
(dissolved) (dissolved)
CaCO3(s) + 2 NaCl(aq)
(solid precipitate)
(dissolved)
A precipitate is an insoluble solid that is formed
by a chemical reaction between two soluble
compounds
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Formation of Carbon Dioxide
acetic acid + sodium hydrogen carbonate 
sodium acetate + carbonic acid
CH3COOH(aq) + NaHCO3(s) 
NaCH3COO(aq) + H2CO3(aq)
NOT the overall reaction because there is NO
carbon dioxide!!!
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Carbonic acid DECOMPOSES into liquid water and
carbon dioxide
H2CO3(aq)  H2O(l) + CO2(g)
OVERALL Reaction
acetic acid + sodium hydrogen carbonate 
sodium acetate + water + carbon dioxide
CH3COOH(aq) + NaHCO3(s) 
NaCH3COO(aq) + H2O(l) + CO2(g)
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Formation of Ammonia
ammonium chloride + sodium hydroxide 
sodium chloride + ammonium hydroxide
NH4Cl(aq) + NaOH(aq)  NaCl(aq) + NH4OH(aq)
NOT the overall reaction because NO ammonia!
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Ammonium hydroxide DECOMPOSES to form water
and ammonia
ammonium hydroxide  water + ammonia
NH4OH(aq)  H2O(l) + NH3(g)
OVERALL Reaction
ammonium chloride + sodium hydroxide 
sodium chloride + water + ammonia
NH4Cl(aq) + NaOH(aq)  NaCl(aq) + H2O(l) + NH3(g)
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Acid reacts with a Base
Products are neither acidic or basic
magnesium hydroxide + hydrochloric acid 
magnesium chloride + water
Mg(OH)2(s) + 2HCl(aq)  MgCl2(aq) + 2H2O(l)
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If one reactant…
is an aqueous salt
is an acid
has ammonium ions
is an acid
+
+
+
+
+
the other
reactant…

then the
products
include
is an aqueous salt

a precipitate
has carbonate ions

water and
carbon dioxide
has hydroxide ions

water and ammonia
has hydroxide ions

water
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Assigned Questions
p. 138 # 1, 2, 3
p. 141 – 143 # 4, 5, 7, 9, 10, 11, 12
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