Chemical Equations for Precipitation Reactions

Objective: Understand how to write equations for reactions between aqueous solutions of FeCl₃ and NaOH.
Results of Mixing: Formation of a precipitate (Fe(OH)₃) and sodium chloride (NaCl) remains in solution.

Molecular Equation
- Definition: Represents the reactants and products using their molecular formulas.
- Example Reaction:
  - Molecular Equation:
  - FeCl₃ (aq) + 3NaOH (aq) → Fe(OH)₃ (s) + 3NaCl (aq)
- Physical States:
  - FeCl₃ - Aqueous (aq)
  - NaOH - Aqueous (aq)
  - Fe(OH)₃ - Solid (s)
  - NaCl - Aqueous (aq)
Complete Ionic Equation
- Definition: Separates the compounds into their ionic forms as they exist in solution.
- Example Reaction:
  - Complete Ionic Equation:
  - Fe³⁺ (aq) + 3Cl⁻ (aq) + 3Na⁺ (aq) + 3OH⁻ (aq) → Fe(OH)₃ (s) + 3Na⁺ (aq) + 3Cl⁻ (aq)
- Notable Points:
  - Describes the individual ions present before and after the reaction.
Net Ionic Equation
- Definition: Simplified equation that shows only the species that participate in the reaction, omitting spectator ions.
- How to Derive:
  - Identify and cancel out the spectator ions (those that appear on both sides of the complete ionic equation).
- Example Reaction:
  - Net Ionic Equation:
  - Fe³⁺ (aq) + 3OH⁻ (aq) → Fe(OH)₃ (s)

Definition: Ions that do not participate in the chemical reaction but are present in the solution.
Example from the Reaction:
- Spectator ions in this case are Na⁺ and Cl⁻.

Understand the three forms of equations for precipitation reactions:
- Molecular Equation - shows all reactants and products in their molecular forms.
- Complete Ionic Equation - shows all ions present in the solution.
- Net Ionic Equation - shows only the species that undergo a chemical change.
Identify which equation format is required based on the problem at hand.