Question

i) Describe how washing soda is produced starting from Sodium Chloride
Write all the reactions involved.
ii) Write any two industrial uses of washing soda
OD​

Answer 1

Answer:

a) Production of washing soda: Washing soda is produced from sodium chloride (or common salt) in the following three steps:

(i) A cold and concentrated solution of sodium chloride (called brine) is reacted with ammonia and carbon dioxide to obtain sodium hydrogen carbonate :



Sodium hydrogencarbonate formed is only slightly soluble in water, so it precipitates out as a solid.

(ii) Sodium hydrogencarbonate is separated by filtration, dried and heated. On heating, sodium hydrogencarbonate decomposes to form sodium carbonate:



The anhydrous sodium carbonate obtained here is called soda ash.

(iii) Anhydrous sodium carbonate (soda ash) is dissolved in water and recrystallised to get washing soda crystals containing 10 molecules of water of crystallisation :



(b) An aqueous solution of washing soda is alkaline because it turns red litmus to blue.

(c) Washing soda has detergent properties because it can remove dirt and grease from dirty clothes.

(d) (i) It is used as cleansing agent for domestic purposes.

(ii) It is used for removing permanent hardness of water.