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प्रश्न
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
उत्तर
Hardness of water is due to the presence of calcium and magnesium ions.
Presence of calcium and magnesium salts in the form of hydrogencarbonate, chloride and sulphate in water makes water ‘hard’. Hard water does not give lather with soap. Water free from soluble salts of calcium and magnesium is called soft water. It gives lather with soap easily.
So, student need to dissolve calcium chloride, calcium sulphate and magnesium sulphate in distilled water to convert it into hard water.
Hence, the correct answer is option (C).
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संबंधित प्रश्न
What happens when a few drops of water are added to anhydrous copper sulphate? Explain with the help of an equation.
What is meant by 'a family of salts'? Explain with examples.
A salt is dissolved in water and the pH of this salt solution is measured with a universal indicator paper. If the pH of solution is less than 7, the salt is most likely to be:
(a) CH3COONa
(b) Na2CO3
(c) KCl
(d) NH4Cl
Give one example of a salt which gives an aqueous solution having:
pH equal to 7
A salt X when dissolved in distilled water gives a clear solution which turns red litmus blue. Explain the phenomenon.
Name a salts whose solubility increases with temperature.
Answer the following questions below, relating your answers only to salts in the following list:
Sodium chloride, anhydrous calcium chloride, copper sulphate-5-water.
(i) What is the name given to the water in the compound copper sulphate-5-water?
(ii) If copper sulphate-5-water is heated, the water is driven off leaving anhydrous copper sulphate. What is the colour of anhydrous copper sulphate?
(iii) By what means, other than heating, you can dehydrate copper sulphate-5-water and obtain anhydrous copper sulphate?
(iv) Which one of the salts in the given list is deliquescent?
Salts A, B, C, D, and E undergo reactions (i) to (v) respectively. Identify the anion present in these salts on the basis of these reactions.
- When silver nitrate solution is added to a solution of A, a white precipitate, insoluble in dilute nitric acid, is formed.
- The addition of dilute hydrochloric acid to B produces a gas which turns lead acetate black paper.
- When a freshly prepared solution of ferrous sulphate is added to a solution of C and concentrated sulphuric acid is gently poured from the side of the test-tube, a brown ring is formed.
- When dilute sulphuric acid is added to D, a gas is produced which turns acidified potassium dichromate solution from orange to green.
- The addition of dilute hydrochloric acid to E produces effervescence. The gas produced turns lime water milky but does not affect acidified potassium dichromate solution.
Write any five uses of salts.
Name the salt formed when sulphuric acid is added to sodium hydroxide and write its pH.
