10.1.2—Reactions of the oxides, hydroxides
- Syllabus
- 9701–2028–2029
- Objective
- 10.1.2
- Level
- AS
Group 2 oxides and hydroxides show systematic reactions with water and acids
Group 2 oxides are basic. Oxides react with water to form hydroxides, and both oxides and hydroxides neutralise acids to form salts and water.
Hydroxide solubility generally increases down the group, so alkaline solutions become easier to obtain. Keep solubility separate from the intrinsic basicity of the oxide lattice.
CaO + H₂O → Ca(OH)₂. The hydroxide then reacts with HCl: Ca(OH)₂ + 2HCl → CaCl₂ + 2H₂O.
Do not treat all Group 2 hydroxides as equally soluble. The reaction can occur at the surface even when the hydroxide is only sparingly soluble.
ConceptA-Level CAIE Chemistry AS