Why washing Soda Effloresce in water?

Washing soda is sodium carbonate decahydrate, Na2CO3.10H2O. Sodium carbonate was made from the ash of sea weeds, once upon a time. It was also found to occur as an efflorescent deposit (Trona, Na2CO3. NaHCO3 . 2H2O) in Egypt. In India, an efflorescent soil called Sajimati, which is a mixture of sodium carbonate, sodium bicarbonate, sodium sulphate and clay is found in places such as Dehradun, Mathura and Varanasi.

Sodium carbonate is one of the most important industrial chemicals. First, anhydrous sodium carbonate is manufactured by the Solvay process (ammonia-soda process) and then it is converted into sodium carbonate decahydrate which is called washing soda.

Washing soda is a transparent, crystalline solid, soluble in water and the solution is found to be alkaline as it turns red litmus blue. Washing soda, the decahydrate of sodium carbonate effloresces in air forming sodium carbonate monohydrate. Efflorescence is the process of losing water of crystallization from a hydrated salt when kept exposed to air for a long time.

Na2CO3 . 10H2O →Na2CO3 . H2O+9H2O

The so formed monohydrate, Na2CO3. H2O is a white amorphous solid, which is stable in air.


1 Comment

  1. Rishabh Gupta

    September 4, 2017 at 7:39 am

    Nice answer
    Our chemistry teacher does not know how to make sentences in English.

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