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प्रश्न
Hardness of water may be temporary or permanent. Permanent hardness is due to the presence of:
(i) Chlorides of \[\ce{Ca}\] and \[\ce{Mg}\] in water.
(ii) Sulphates of \[\ce{Ca}\] and \[\ce{Mg}\] in water.
(iii) Hydrogen carbonates of \[\ce{Ca}\] and \[\ce{Mg}\] in water.
(iv) Carbonates of alkali metals in water.
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उत्तर
(i) Chlorides of \[\ce{Ca}\] and \[\ce{Mg}\] in water.
(ii) Sulphates of \[\ce{Ca}\] and \[\ce{Mg}\] in water.
Explanation:
Presence of calcium and magnesium salts in the form of hydrogen carbonate, chloride and sulphate in water makes water ‘hard’.
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संबंधित प्रश्न
What is meant by ‘demineralised’?
Is demineralised or distilled water useful for drinking purposes? If not, how can it be made useful?
The oxide that gives \[\ce{H2O2}\] on treatment with dilute \[\ce{H2SO4}\] is ______.
When sodium peroxide is treated with dilute sulphuric acid, we get ______.
Which of the following ions will cause hardness in water sample?
Which of the following compounds is used for water softening?
Complete the following equations:
\[\ce{PbS (s) + H2O2 (aq) ->}\]
Complete the following equations:
\[\ce{CO (g) + 2H2 (g) ->[Cobalt][Catalyst]}\]
Discuss briefly de-mineralisation of water by ion exchange resin.
Why is the Ionisation enthalpy of hydrogen higher than that of sodium?
Match the items in Column I with the relevant item in Column II.
| Column I | Column II |
| (i) Hydrogen peroxide is used as a | (a) zeolite |
| (ii) Used in Calgon method | (b) perhydrol |
| (iii) Permanent hardness of hard water is removed by | (c) sodium hexametaphosphate |
| (d) propellant |
Assertion (A): Permanent hardness of water is removed by treatment with washing soda.
Reason (R): Washing soda reacts with soluble magnesium and calcium sulphate to form insoluble carbonates.
Which one of the following methods is most suitable for preparing deionized water?
100 ml of a water sample contains 0.81 g of calcium bicarbonate and 0.73 g of magnesium bicarbonate. The hardness of this water sample expressed in terms of equivalent of CaCO3 is ______.
[Molar mass of calcium bicarbonate is 162 g mol-1 and magnesium bicarbonate is 146 g mol-1)
