Sodium chloride, NaCl
Sodium chloride, NaCl
The most
abundant source of sodium chloride is sea water which contains 2.7 to 2.9% by mass
of the salt. In tropical countries like India, common salt is generally
obtained by evaporation of sea water. Approximately 50 lakh tons of salt are
produced annually in India by solar evaporation. Crude sodium chloride,
generally obtained by crystallization of brine solution, contains sodium
sulphate, calcium sulphate, calcium chloride and magnesium chloride as
impurities. Calcium chloride, CaCl2, and magnesium chloride, MgCl2
are impurities because they are deliquescent (absorb moisture easily from the
atmosphere). To obtain pure sodium chloride, the crude salt is dissolved in
minimum amount of water and filtered to remove insoluble impurities. The solution
is then saturated with hydrogen chloride gas. Crystals of pure sodium chloride separate
out. Calcium and magnesium chloride, being more soluble than sodium chloride,
remain in solution.
Sodium chloride
melts at 1081K. It has a solubility of 36.0g in 100 g of water at 273 K. The
solubility does not increase appreciably with increase in temperature.
Uses
- It is used as a common salt or table salt for domestic purpose.
- It is used for the preparation of Na2O2, NaOH and Na2CO3.
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