How washing soda is obtained from sodium
chloride? Write balanced chemical equation
Answers
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 chloride (common salt)
NaCl
+
Ammonia
NH
3
+
Water
H
2
O
+
Carbon dioxide
CO
2
→
Sodium hydrogencarbonate
NaHCO
3
+
Ammonium chloride
NH
4
Cl
Sodium hydrogen carbonate formed is only slightly soluble in water, so it precipitates out as a solid.
(ii) Sodium hydrogen carbonate is separated by filtration, dried and heated. On heating, sodium hydrogen carbonate decomposes to form sodium carbonate:
Sodium hydrogencarbonate
2NaHCO3
Heat
Sodium crbonate (soda ash)
Na2CO3+CO2+ H2O
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 :
Anhydrous sodium carbonate (Soda ash)
Na2CO3 + 10H2O
⟶
Sodium carbonate decahydrate (washing soda)
Na2CO3 .10H2O
(b) An aqueous solution of washing soda is alkaline because it is made of a strong base and a weak acid.
(c) Washing soda has detergent properties because it can remove dirt and grease from dirty clothes.
(d) Two important uses of washing soda are-
(i) It is used as a cleansing agent for domestic purposes.
(ii) It is used for removing permanent hardness of water.