Washing soda

The chemical name of washing soda is sodium carbonate decahydrate, and its chemical formula is Na₂CO₃.10H₂O. So washing soda is hydrated salt of sodium carbonate containing 10 molecules of water of crystallization. But the anhydrous sodium carbonate which doesn’t have any molecule of water of crystallization is commonly known as ‘soda ash’.

Sodium carbonate occurs in crude forms in East Africa, Egypt, USA etc. In India it occurs in Dehradun, Mathura, Jaunpur, Varanasi, etc. About 1.54 million tons of soda ash (anhydrous sodium carbonate) is produced in India every year.

Properties of Washing Soda

1. Washing soda is a transparent crystalline solid.
2. Washing soda is soluble in water
3. The aqueous solution of Washing soda is alkaline in nature i.e. it converts red litmus paper into blue.
4. Washing Properties:- Washing soda is used as a detergent for washing the clothes because it can attack on the dirt and grease particles present in dirty clothes to remove them.
5. Reaction with Water:- Washing soda decomposes into ions when dissolved in water to produce alkaline solution.

           Na₂CO₃            2Na⁺      +      CO₃^2–

            2H₂O            2H⁺      +      2OH^–

   2Na⁺ + CO₃^2– + 2H⁺ + 2OH^–        2NaOH + H₂CO₃

   The ionic solution of washing soda is alkaline in nature due to the presence of OH^– ions in it.

6. Action of Air:- Washing soda crystals are when exposed to air then 9 molecules of water of crystallization evaporates leaving behind sodium carbonate monohydrate which is in the form of white powder.

   Na₂CO₃.10H₂O          NaCO₃.H₂O    +    9H₂O
   Washing soda                              Sodium carbonate      Water
                                                           decahydrate

   Efflorescence or Dehydration

   The loss of water of crystallization from the hydrated salt of washing soda to the environment, on keeping it exposed to air, is called efflorescence.

Action of Heat:- When the crystals of washing soda are heated strongly then all the water of crystallization evaporates leaving behind anhydrous sodium carbonate.

Na₂CO₃.10H₂O          NaCO₃      +      10H₂O
Washing soda                           Sodium carbonate       Water

Uses of Washing Soda

1. Washing soda is used extensively for washing clothes in laundry.
2. Washing soda is used for softening hard water.
3. Washing soda is used in the manufacture of many useful compounds such as caustic soda, borax, glass and soap.
4. Washing soda is also used as a laboratory reagent.

Test your understanding and answer these questions:

1. What is chemical name and formula of washing soda?
2. How washing soda is prepared?
3. Give uses of washing soda.