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Question
Distinguish by a chemical test sodium chloride and sodium sulphite.
Solution 1
The salts can be distinguished by using silver acetate. To the salt, silver acetate and dil. HNO3 are added. If there is formation of a white precipitate that slowly turns black then it is thiosulphate anion since silver acetate forms Ag2S2O3 which being unstable in acid solution gets converted to black Ag2S.
Solution 2
\[\ce{NaCl + H2SO4 -> NaHSO4 + HCl}\]
\[\ce{Na2SO3 + H2SO4 -> Na2SO4 + H2O + SO2}\]
When sodium sulphite reacts with H2SO4 to produce sulphur dioxide gas, sodium chloride reacts with H2SO4 to produce HCl gas.
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The Salt Story
From: The New Indian Express 9 March 2021
The salt pans in Marakkanam, a port town about 120 km from Chennai are the third largest producer of salt in Tamil Nadu. Separation of salt from water is a laborious process and the salt obtained is used as raw materials for manufacture of various sodium compounds.
One such compound is Sodium hydrogen carbonate, used in baking, as an antacid and in soda acid fire extinguishers.
The table shows the mass of various compounds obtained when 1litre of sea water is evaporated.
| COMPOUND | FORMULA | MASS OF SOLID PRESENT /g |
| Sodium Chloride | NaCl | 28.0 |
| Magnesium Chloride | MgCl2 | 8.0 |
| Magnesium Sulphate | MgSO4 | 6.0 |
| Calcium Sulphate | CaSO4 | 2.0 |
| Calcium Carbonate | CaCO3 | 1.0 |
| TOTAL AMOUNT OF SALT OBTAINED | 45.0 | |
How many grams of Magnesium Sulphate are present in 135g of solid left by evaporation of sea water?
