1. Calcium Oxide (CaO) Reacts with Water
When calcium oxide is added to water, it undergoes a chemical reaction to form calcium hydroxide (Ca(OH)₂), also known as slaked lime:
CaO (s) + H₂O (l) → Ca(OH)₂ (aq)
2. Calcium Hydroxide is a Base
Calcium hydroxide is a strong base. This means it readily donates hydroxide ions (OH-) to the solution:
Ca(OH)₂ (aq) → Ca²⁺ (aq) + 2OH⁻ (aq)
3. Hydroxide Ions Determine Basicity
The presence of hydroxide ions (OH-) in the solution is what makes it basic. The higher the concentration of OH- ions, the stronger the base.
In summary:
- Calcium oxide reacts with water to form calcium hydroxide.
- Calcium hydroxide is a strong base that releases hydroxide ions into the solution.
- The presence of hydroxide ions makes the solution basic.
Therefore, an aqueous solution of calcium oxide is basic due to the formation of calcium hydroxide and its subsequent dissociation into hydroxide ions.
