4.4 TYPES OF REACTIONS: DOUBLE DISPLACEMENT REACTIONS



Involves two compounds reacting to form two new compounds
The ions are exchanged in this reaction
Indicators of a double displacement reaction: precipitate forms, gas is produced, formation
of molecular compound
Consider Double Displacement using the analogy of the TV Show Wife Swap:
AB
CD
AD
CB
I) PRECIPITATE IS PRODUCED
 When two solutions react, the cations in one solution can attract and bond with the
anions in another solution.
 We have to have some understanding of solubility to predict whether certain products
will be soluble of not. Remember the definitions of the following key words regarding
solubility:
o Solution
o Solute
o Solvent


We can predict which products of a double displacement reaction will form precipitates
using the solubility chart in your Study Aid or on Page 173 in your text.
NOTE: If both products end up being soluble, there is no reaction and we write NR
Anion
Any anion
Nitrate (NO31-)
Acetate (CH3COO1-)
Chloride (Cl1-),
Bromide (Br1-), or
Iodide (I1-)
+ Cation
+ Group IA (Li+, Na+, K+, Rb+, Cs+,
NH4+)
+ Any cation
+ Any cation except Ag+
+
Ag+, Pb2+, Hg22+, Cu2+
+
Any other cation
+
+
+
Sulfide (S2-)
+
+
+
Hydroxide (OH1-)
+
+
Phosphate (PO43-), Carbonate +
(CO32-), or Sulfite (SO32-)
Sulfate (SO42-)
2+
2+
2+
Solubility
Soluble
Soluble
Soluble
Not soluble
Soluble
2+
+
2+
Ca , Sr , Ba , Ra , Ag , Pb
Any other cation
Group IA or NH4+
Be2+, Mg2+, Ca2+, Sr2+, Ba2+, Ra2+
Any other cation
Group IA or NH4+
Sr2+, Ba2+, Ra2+
Any other cation
Group IA or NH4+
Not soluble
Soluble
Soluble
Soluble
Not soluble
Soluble
Slightly soluble
Not soluble
Soluble
Example:
BaCl2(aq)
K2SO4(aq)
+
→
+
Examples:
AgNO3
+
K2SO4
→
NH4Cl
+
Na2S
→
II) GAS IS PRODUCED
 Sometimes more than one reaction occurs to produce the gas
 When acids react with sulfides (e.g. K2S), they produce hydrogen sulfide (e.g. H2S)
 When acids react with carbonates (e.g. Na2CO3), they produce carbon dioxide, CO2
 When acids react with sulfites (e.g. K2SO3), they produce sulfur dioxide, SO2
Example:
Mg(CO3)2(aq) + H2SO4(aq) →
______________________________________________________________
III) NEUTRALIZATION REACTIONS
 The reaction of an acid and a base
 The resulting mixture ends with a pH of close to
.
 Neutralization reactions are widely used in the science of heartburn and relief from acid
indigestion.
General Formula: Acid + Base → Water + Ionic Salt
Example:
HNO3(aq) + NaOH(aq) →
____
Mg(OH)2(s) + ____ HCl(aq) →