TYPES OF SOLUTION CHEMICAL REACTIONS
PRECIPITATION REACTIONS
When we are speaking of solution chemistry, virtually all chemical reactions fall into three types:
a) Precipitation reactions b) Acid-Base reactions c) Oxidation-Reduction reactions.
Precipitation Reactions
1. A double replacement reaction where the reactants are solutions (aq).
The products may be solutions (aq) or precipitates (s)
Reactant (aq) + Reactant (aq)  Product (aq) + Product (aq)
Reactant (aq) + Reactant (aq)  Product (s) + Product (aq)
Reactant (aq) + Reactant (aq)  Product (s) + Product (s)
2. To predict the outcome of the reaction and write the equation:
a. Use the chemical formulas of the reactants to determine the ions that are present.
b. Write the chemical formulas of the products by combining the cations from one reactant
with the anion of the other reactant. Use the charges of the ions to determine the subscripts in
the chemical formula (CRISS-CROSS).
c. Determine if any products are insoluble according to the solubility rules you
MEMORIZED.
Exercise 8
Using the solubility rules, predict what will happen when the following pairs of solutions are
mixed.
a. KNO3(aq) and BaC12(aq)
b. Na2SO4(aq) and Pb(NO3)2(aq)
c. KOH (aq) and Fe(NO3)3(aq)
b. PbSO4 (s)
c. Fe(OH)3 (s)
3. Describing reactions in solution:
a. Molecular Equation- shows the complete chemical formulas of the reactants and products
without indicating their ionic character.
Na2SO4(aq) + Pb(NO3)2(aq)  2Na(NO3)(aq) + PbSO4 (s)
b. Complete Ionic Equation- all substances that are strong electrolytes are represented as ions.
Solids, pure liquids and gases cannot be ionized. Subscripts next to an atom are shown as the
coefficient in an ionic equation in order to conserve charge.
2Na+(aq) + SO4-2(aq) + Pb+2(aq) + 2NO3-(aq)  2Na+(aq) + 2NO3-(aq) + PbSO4 (s)
c. Net Ionic Equation- Includes only the ions and molecules directly involved in the reaction.
i. Spectator Ions- ions that appear in identical forms as a reactant and a product. They
are omitted from the net ionic equation.
ii. If all ions are spectator ions the reaction Does Not Occur
SO4-2(aq) + Pb+2(aq)  PbSO4 (s)
4. Stoichiometry Problems and Precipitation Reactions
A. Steps for Success
1. Write the balanced net ionic equation for the reaction.
2. Calculate the moles of each reactant.
3. Determine which reactant is limiting.
4. Calculate the moles of products formed by limiting reactant.
5. Convert to grams.
Exercise 10
Calculate the mass of solid NaC1 that must be added to 1.50 L of a 0.100 M AgNO3 solution to
precipitate all the Ag+ ions in the form of AgC1.
8.77 g NaC1
Exercise 11
When aqueous solutions of Na2SO4 and Pb(NO3)2 are mixed, PbSO4 precipitates. Calculate the
mass of PbSO4 formed when 1.25 L of 0.0500 M Pb(NO3)2 and 2.00 L of 0.0250 M Na2SO4 are
mixed.
5.2 g PbSO4