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Hydrogen

Short Answer Type

131. Do you expect different products in solution when aluminium (III) chloride and potassium chloride are treated separately with:
(i) normal water (ii) acidifed water and (iii) alkaline water?

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132.

What is hard and soft water?

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Long Answer Type

133. What causes the temporary and permanent hardness of water?
Or
Distinguish clearly between temporary hardness and permanent hardness.
Or
What is hardness of water due to? What are its types?

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Short Answer Type

134.
Why does hard water not form lather with soap?

Soap is sodium or potassium salt of certain long chain fatty acids such as stearic acid, palmitic acid, oleic acid etc. When hard water is treated with soap solution, Ca²⁺and Mg²⁺ ions present in hard water react with the anions of fatty acids present in the soap to form a scum (curdy white precipitate).

Soap will not produce a lather with hard water until all the calcium and magnesium ions have been precipitated as stearates. Hard water thus wastes soap.

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Long Answer Type

135.

What are different methods used for softening of hard water?

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136. What is ‘demineralised water’ and how can it be obtained?

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137. Discuss the principle and method of softening of hard water by synthetic ion-exchange resins.
Or
What do you mean by synthetic ion-exchange resins?

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