Explain by writing a word equation.
Hard water gets softened on mixing with a solutions of washing soda.
Sodium carbonate, Na2CO3, is also known as washing soda. It can remove temporary and permanent hardness from water. Sodium carbonate is soluble but calcium carbonate and magnesium carbonate are insoluble.
The carbonate ions from sodium carbonate reacts with calcium and magnesium ions in the water to produce insoluble precipitate.
Ca2 + (aq) + Na2Co3 → CaCO3(s) + 2Na+(aq)
The water is softened because it no longer contains dissolved calcium ions and magnesium ions.