South Pasadena • Honors Chemistry
Name
5 • Chemical Reactions
Period
5.2
NOTES
Date
– REACTIONS IN AQUEOUS SOLUTION
Writing Net Ionic Equations
Strong electrolytes (i.e. strong acids, strong bases, and soluble salts) dissociate 100% into ions, and are better
represented as separate ions. For example, “a solution of sodium chloride” should be written as “Na+ (aq) + Cl‒
(aq)” rather than than as “NaCl (aq)”. (Note: do NOT dissociate solids, liquids, or gases into ions.)
Step 1: Write the balanced molecular equation.
Step 2: Write the complete ionic equation: write strong acids, strong bases, and soluble salts as ions.
Step 3: Write the net ionic equation: Drop any ions that show up exactly the same on both sides of the equation
(spectator ions).
Example: Solutions of calcium chloride and silver nitrate are combined.
Ca2+ + Cl–
Ag+ + NO3–
Balanced Molecular Equation:
Before Reaction
CaCl2 (aq) + 2 AgNO3 (aq) →
Ca(NO3)2 (aq) + 2 AgCl (s)
After Reaction
Complete Ionic Equation:
Ca2+ + 2 Cl– + 2 Ag+ + 2 NO3– →
Ca2+ + 2 NO3– + 2 AgCl (s)
Net Ionic Equation:
2 Ag+ + 2 Cl– → 2 AgCl (s)
or
Ag+ + Cl– → AgCl (s)
Note: Ca2+ and NO3– are canceled out as spectator ions.
Double Replacement Reactions
 Also called “double displacement” or “metathesis” reactions.
 Take place when aqueous solutions of relatively ionic compounds (i.e. ionic compounds, acids, or water) are
combined.
 General form: AX + BY  AY + BX
(A and B are cations and X and Y are anions)
 Sub-Types of Double Replacement Reactions:
 Precipitation Reaction: one product is an insoluble salt, or precipitate.
 Gas-Forming Reaction: one product is a substance that forms a gas in aqueous solution. Here are some
common gases that form:
o  H2S (g)
o  H2SO3 (aq)  SO2 (g) + H2O (ℓ)
o  H2CO3 (aq)  CO2 (g) + H2O (ℓ)
o  NH4OH (aq)  NH3 (g) + H2O (ℓ)
 Neutralization Reaction: ACID + BASE → SALT + H2O
When given relatively ionic reactants, here are the steps to predict the products.
1. Identify the ions in the reactants.
2. Recombine the cations and anions to form new compounds in the products.
3. Identify the states of the compounds. Use the solubility rules. At least one of the products should be a
precipitate, weak electrolyte, or a gas-forming substance.
4. Balance the equation.
Examples: Write the complete molecular and net ionic equations for each of the following reactions.
 Solutions of potassium chromate and silver nitrate are combined.
K2CrO4 (aq) + 2 AgNO3 (aq) → 2 KNO3 (aq) + Ag2CrO4 (s)
2 Ag+ + CrO42– → Ag2CrO4 (s)

A solution of sodium bicarbonate (baking soda) is combined with a solution of acetic acid (vinegar).
NaHCO3 (aq) + HC2H3O2 (aq) → NaC2H3O2 (aq) + H2O (ℓ) + CO2 (g)
HCO3– + HC2H3O2 (aq) → C2H3O2– (aq) + H2O (ℓ) + CO2 (g)

Al(ClO3)3 (aq) + KOH (aq)
Al(ClO3)3 (aq) + 3 KOH (aq) → 3 KClO3 (aq) + Al(OH)3 (s)
Al3+ + 3 OH– → Al(OH)3 (s)

Solid cupric acetate is dropped in water.
Cu(C2H3O2)2 (s) + 2 H2O (ℓ) → 2 HC2H3O2 (aq) + Cu(OH)2 (s)
Cu(C2H3O2)2 (s) + 2 H2O (ℓ) → 2 HC2H3O2 (aq) + Cu(OH)2 (s)