Reactions in Aqueous
Solutions
Section 10.3
Objectives
 Describe aqueous solutions
 Write complete ionic and net ionic
equations for chemical reactions in
aqueous solutions
 Predict whether reactions in aqueous
solutions will produce a precipitate, water,
or gas.
Key Terms
 Solute
 Solvent
 Aqueous solution
 Complete ionic equation
 Spectator ion
 Net ionic equation
Review of Solutions
 Solvent- More plentiful substance in solution
 Solute- The compound dissolved in the solvent
 Aqueous solution- Solution in which the solvent
is water
Aqueous Solutions
 Many possible solutes:
– Molecular compounds that exist as
molecules
• Sucrose
• Ethanol
– Molecular compounds that exist as ions
• HCl
HCl(g)  H + (aq) = Cl- (aq)
Aqueous Solutions (cont)
– Ionic compounds that exist as ions
• NaOH
NaOH(aq)  Na + (aq) + OH- (aq)
Aqueous Solutions
 When two aqueous solutions containing ions
react it is always a double replacement reaction.
 The water does not react
 There are three possible products when aqueous
solutions react:
– Precipitates
– Water
– Gases
Reactions that form Precipitates
 Double-replacement reaction
2NaOH(aq) + CuCl2 (aq)  2NaCl (aq) + Cu(OH)2(s)
 Ionic equations are used to show the details of
reactions involving ions
Writing Ionic Equations
 You must show the reactants and the product as
ions
 A complete ionic equation shows all of the
particles in the solution as they realistically exist.
 A net ionic equation only shows particles that
participate in the reaction.
 To write a net ionic equation from a complete
ionic equation eliminate all spectators.
Complete Ionic Equations
 AgNO3(aq) + NaCl(aq)  AgCl(s) + NaNO3(aq)
 What type of reaction is this?
 Ag+(aq) + NO3-(aq) + Na+ (aq) + Cl-(aq) 
AgCl(s) + Na+ (aq) + NO3-(aq)
Spectator Ions

Ag+(aq) + NO3-(aq) + Na+(aq) + Cl(aq)  AgCl(s) + Na+(aq) + NO3-(aq)
 Ions that are not directly involved in a
reaction are called spectator ions
– They appear on both sides of the arrow exactly
the same way
Net Ionic Equation
 Eliminate spectators and rewrite the
equation

Ag+(aq) + Cl-(aq)  AgCl(s)
Ionic Equations
 Make sure that the net charge is balanced.
For example…

Pb(s) + 2Cl-(aq)  PbCl2(s)
Reactions that Form Water
 Double-replacement reactions
 Water molecules increase the number of
solvent particles
 No evidence of reaction is observable
(water is colorless and odorless)
HBr(aq) + NaOH(aq)  H2O (l) + NaBr(aq)
Practice
 Write the complete ionic and net ionic
equations for the example:
HBr(aq) + NaOH(aq)  H2O (l) + NaBr(aq)
Reactions that Form Gases
 Double-replacement reactions
 Gas-producing
 Common gases:
– Carbon dioxide
– Hydrogen cyanide
– Hydrogen sulfide
Practice
 Write the complete and net ionic equations
for this gas-producing reaction:
2HI(aq) + Li2S(aq)  H2S(g) + 2LiI(aq)
Homework
 47-51 on page 299