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Question
A solution of a substance ‘X’ is used for white washing.
- Name the substance ‘X’ and write its formula.
- Write the reaction of the substance ‘X’ named in (i) above with water.
Solution
- The substance ‘X’ is calcium oxide. Its chemical formula is CaO.
- Calcium oxide reacts with water to form calcium hydroxide. \[\ce{\underset{(X)}{CaO_{(s)}} + H2O_{(l)} -> \underset{Calcium hydroxide}{Ca(OH)2_{(aq)}}}\]
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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 | |
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