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प्रश्न
The metal salt A is blue in colour. When salt A is heated strongly over a burner, then a substance B is eliminated and a white powder C is left behind. When a few drops of a liquid D are added to powder C, it becomes blue again. What could be A, B, C and D?
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उत्तर
A is copper sulphate pentahydrate, CuSO4.5H2O; B is water of crystallisation, 5H2O; C is anhydrous copper sulphate, CuSO4; D is water, H2O.
The blue colour of copper sulphate is due to the presence of 5 water molecules. When copper sulphate crystals are heated, they lose their water molecules and turn into a grey-white powder known as anhydrous copper sulphate. The chemical équation for this process is:
\[\ce{CuSO4 * 5H2O -> CuSO4 + 5H2O}\]
After adding a few drops of water (D), the anhydrous copper sulphate rehydrates into copper sulphate pentahydrate, and due to the re-entry of water molecules into its crystal lattice, it becomes blue again. The chemical equation for this process is:
\[\ce{CuSO4 + 5H2O -> CuSO4 * 5H2O}\]
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संबंधित प्रश्न
Identify the substance underlined, in the following case
A solid formed by reaction of two gases, one of which is acidic and the other basic in nature
From the list of the following salts choose the salt that most appropriately fits the
description is given in the following:
[AgCl, MgCl2, NaHSO4, PbCO3, ZnCO3, KNO3, Ca(NO3)2]
On heating, this salt gives a yellow residue when hot and white when cold
From the list of the following salts choose the salt that most appropriately fits the
description is given in the following:
[AgCl, MgCl2, NaHSO4, PbCO3, ZnCO3, KNO3, Ca(NO3)2]
On heating this salt, a brown colored gas is evolved.
Name three chemicals made from common salt (or sodium chloride).
Common salt is obtained from sea-water by the process of ______.
Complete and balance the following chemical equation:
\[\ce{NaCl_{(aq)} + H2O_{(l)} ->[Electricity]}\]
What is meant by ‘a family of salts’? Explain with examples.
Give one example of a salt which gives an aqueous solution having:
pH less than 7
Give one example of a salt which gives an aqueous solution having:
pH equal to 7
Consider the following salts:
Na2CO3, NaCl, NH4Cl, CH3COONa, K2SO4, (NH)2SO4
Which of these salts will give:
- acidic solutions?
- neutral solutions?
- basic solutions (or alkaline solutions)?
Write the name and formula of one salt which contains:
Five molecules of water of crystallisation.
What is a ‘salt’?
Name a salt whose solubility decreases with temperature.
You are asked to prepare hard water in your laboratory. Select a group from the following groups of salts, any salt of which you may dissolve in distilled water to obtain hard water.
(A) NaCl; Na2SO4; KCl
(B) NaCl; CaCl2; KCl
(C) CaCl2; CaSO4; MgSO4
(D) Na2SO4; CaSO4; MgSO4
Define the following term:
Efflorescence
Taking sodium carbonate as an example, give the meaning of the following terms:
Water of crystallization
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 | |
What is the pH of the acid which is used in the formation of common salt?
A salt that is formed by the complete neutralization of an acid and a base is called ______ salt.
