Role of Sodium Carbonate in Softening of hard water

On heating, washing soda gives anhydrous sodium carbonate called soda ash.

Na2CO3 . 10H2O →Na2CO3 + 10H2O

Major applications:

Sodium carbonate is used

  • In the manufacture of paper, soap, textiles, paints, etc.
  • In laundry as washing soda and as a cleaning agent for domestic purposes.
  • As an important laboratory reagent both in qualitative and quantitative analysis.
  • In softening of hard water.

Hardness of water is due to the presence of soluble salts of calcium and magnesium. When washing soda is dissolved in hard water, calcium and magnesium salts which cause hardness, react with washing soda and gets precipitated as insoluble solids, thus leaving the water soft.

Na2CO3 + MgSO4 →Na2SO4 + MgCO3 ¯


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