Neutrality of Calcium Sulphate Solution
Calcium sulphate (CaSO₄) is a salt formed from a strong acid (sulphuric acid) and a weak base (calcium hydroxide).
- When dissolved in water, calcium sulphate dissociates into calcium ions (Ca²⁺) and sulphate ions (SO₄²⁻).
- The resulting solution has no excess H⁺ or OH⁻ ions, leading to a neutral pH around 7.
- The weak base (calcium hydroxide) does not significantly affect the acidity, resulting in a balanced solution.
Basic Nature of Sodium Carbonate Solution
Sodium carbonate (Na₂CO₃) is a salt derived from a strong base (sodium hydroxide) and a weak acid (carbonic acid).
- In an aqueous solution, sodium carbonate dissociates into sodium ions (Na⁺) and carbonate ions (CO₃²⁻).
- The carbonate ions react with water in a hydrolysis reaction to produce hydroxide ions (OH⁻):
- CO₃²⁻ + H₂O ⇌ HCO₃⁻ + OH⁻
- The generation of hydroxide ions increases the concentration of OH⁻ in the solution, resulting in a basic pH, typically above 7.
Conclusion
- Calcium sulphate remains neutral due to the balance of ions and lack of free H⁺ or OH⁻ ions.
- Sodium carbonate is basic because it produces hydroxide ions through hydrolysis, increasing the pH of the solution.
Understanding these properties helps in predicting the behavior of different salt solutions in various chemical contexts.