Aluminum Hydroxide Precipitation
AlCl3 + 3NaOH → Al(OH)3↓ + 3NaCl
Overview
Aluminum chloride reacts with sodium hydroxide to form a white gelatinous precipitate of aluminum hydroxide (Ksp = 3 × 10⁻³⁴). Al(OH)₃ is amphoteric: it dissolves in excess NaOH to form aluminate [Al(OH)₄]⁻. The gelatinous precipitate is an excellent flocculating agent.
Participants
| Role | Substance | Coefficient | State |
|---|---|---|---|
| Product | Aluminum Hydroxide Al(OH)₃ | 1 | (s) |
| Product | Sodium Chloride NaCl | 3 | (aq) |
Everyday Example
Water treatment plants use aluminum salts to form Al(OH)₃ flocs that trap suspended particles, clarifying drinking water.
Industrial Importance
Al(OH)₃ coagulation is the most widely used water purification method globally. Aluminum hydroxide is also used as a fire retardant and antacid.
Properties
- Type
- Precipitation
- Reversible
- No
- Energy
- Exothermic
- ΔH
- -115.0 kJ/mol
Related Reactions
Barium Carbonate Precipitation
Barium Sulfate Precipitation
Cadmium Sulfide Precipitation (Yellow)
Calcium Carbonate Precipitation
Calcium Fluoride Precipitation (Fluorite)
Calcium Oxalate Precipitation (Kidney Stones)
Calcium Phosphate Precipitation (Bone Mineral)
Calcium Sulfate Precipitation (Gypsum)
Chromium(III) Hydroxide Precipitation
Cobalt(II) Hydroxide Precipitation
Frequently Asked Questions
What is the equation for Aluminum Hydroxide Precipitation?
The balanced equation is: AlCl₃ + 3NaOH → Al(OH)₃↓ + 3NaCl.
What type of reaction is Aluminum Hydroxide Precipitation?
Aluminum Hydroxide Precipitation is a precipitation reaction.
Is Aluminum Hydroxide Precipitation exothermic or endothermic?
Aluminum Hydroxide Precipitation is exothermic (releases energy). The enthalpy change (ΔH) is -115.0 kJ/mol.