Group 2 Oxides & Water
- Group 2 oxides react with water, releasing hydroxide ions, to form alkaline solutions:
CaO (s) + H2O (l) → Ca2+ (aq) + 2OH- (aq)
- These solutions get more alkaline going down the group
- This is due to increasing solubility meaning the resulting solutions formed contain more OH- ions
- When the solution becomes saturated any further metal and hydroxide ions will form a precipitate:
Ca2+ (aq) + 2OH- (aq) → Ca(OH)2 (s)
- Solid magnesium hydroxide, Mg(OH)2 (s), is only slightly soluble in water
- The solution has a low OH-(aq) concentration and a pH ≅ 10
- Barium hydroxide, Ba(OH)2 (s), is much more soluble in water
- The solution has a greater OH-(aq) concentration and a pH ≅ 13