Reactions in Aqueous Solutions
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Solutions (textbook p. 434-443)
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Aqueous Solution – A solution in which the
solvent is water.
Water is the solvent (does the dissolving).
Water will dissolve polar molecules and ionic
compounds.
Solutes that are dissolved in water form ions
(charged atoms/polyatomic ions).
Double displacement reactions have ions that
may react with one another.
These reactions can form a precipitate,
water, or a gas.
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Ionization – process of water dissolving polar
molecules. The water pulls the polar molecule
apart and forms ions.
Acids go through ionization and form H+ ions.
H+ ions form hydronium ions, H3O+
HCl(aq) + H2O(l) → H3O+(aq) + Cl-(aq)
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Dissociation – ionic compounds are separated
by the polar molecules into ions.
NaOH(aq) → Na+(aq) + OH-(aq)
Dissociation of NaCl
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Ionic Equations
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Chemical Equation – shows the reactants and
products in a chemical reaction.
2NaOH(aq) + CuCl2(aq) → 2NaCl(aq) + Cu(OH)2(s)
Complete Ionic equations show the substances
as they exist as ions in solution.
2Na+(aq) + 2OH-(aq) + Cu2+(aq) + 2Cl-(aq) →
2Na+(aq) + 2Cl-(aq) + Cu(OH)2(s)
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Spectator ions – ions that do not participate
in the reaction. They are found on both sides
of the equation.
2Na+(aq) + 2OH-(aq) + Cu2+(aq) + 2Cl-(aq) →
2Na+(aq) + 2Cl-(aq) + Cu(OH)2(s)
Net Ionic Equation – Includes only the
particles that participate in the reaction.
2OH-(aq) + Cu2+ (aq) → Cu(OH)2(s)
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Forming a Precipitate
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The net ionic equation results in an insoluble compound.
This insoluble compound is a precipitate.
There are guidelines to determine if the compound is
soluble or insoluble.
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Forming Water
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Double displacement reaction sometimes
produces water.
Increases the number of solvent particles.
There is no real observable evidence of this
type of reaction because water is colorless
and odorless.
Usually a neutralization reaction between an
acid and a base.
This reaction forms a salt and water.
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HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq) → Na+(aq) +
Cl-(aq) + H2O(l)
H+(aq) + OH-(aq) → H2O(l)
Neutralization Reaction Movie
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Forming a Gas
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Double displacement reactions can form gases.
Nonpolar gases such as carbon dioxide (CO2),
Hydrogen cyanide (HCN), and hydrogen
sulfide (H2S)
2HI(aq) + Li2S(aq) → H2S(g) + 2LiI(aq)
2H+(aq) + 2I-(aq) + 2Li+(aq) + S2-(aq) →
H2S(g) + 2Li+(aq) + 2I-(aq)
2H+(aq) + S2-(aq) → H2S(g)
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Carbonate (CO32-)and bicarbonate (HCO3-)
react with acids to form carbon dioxide gas.
Carbonic acid (H2CO3) is formed in a double
displacement reaction.
The unstable carbonic acid decomposes into
carbon dioxide and water.
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HCl(aq) + NaHCO3(aq) → H2CO3(aq) + NaCl(aq)
H2CO3(aq) → H2O(l) + CO2(g)
Overall :
HCl(aq) + NaHCO3(aq) → H2O(l) + CO2(g) + NaCl(aq)
H+(aq) + Cl-(aq) + Na+(aq) + HCO3-(aq) →
H2O(l) + CO2(g) + Na+(aq) + Cl-(aq)
H+(aq) + HCO3-(aq) → H2O(l) + CO2(g)
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Examples
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HBr(aq) + KOH(aq) → ?
H+(aq) + Br-(aq) + K+(aq) + OH-(aq) → H2O(l) + K+(aq) + Br-(aq)
H+(aq) + OH-(aq) → H2O(l)
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HNO3(aq) + Na2CO3(aq) → ?
2HNO3(aq) + Na2CO3(aq) → H2CO3(aq) + 2NaNO3(aq)
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But H2CO3 will decompose into CO2 + H2O
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2H+(aq)+2NO3-(aq)+2Na+(aq)+CO32-(aq)→ H2O(l) + CO2(g) +2Na+(aq)+2NO3-
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2H+(aq) + CO32-(aq) → H2O(l) + CO2(g)
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19. Aqueous solutions of barium chloride and
sodium fluoride are mixed to form a
precipitate of barium fluoride.
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20. Aqueous solutions of copper(I) nitrate and
potassium sulfide are mixed to form insoluble
copper(I) sulfide.
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21. Hydrobromic acid (HBr) reacts with aqueous
lithium hydroxide.
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22. Hydrochloric acid reacts with aqueous lithium
cyanide.
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23. Perchloric acid (HClO4) reacts with aqueous
rubidium hydroxide.
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