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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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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134.
Why does hard water not form lather with soap?
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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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Short Answer Type
138.
How will you prepare a sample of temporary hard water from lime water? Write equation for the reactions involved.
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139.When hard water is boiled in electric kettle, a white scale gets formed inside the kettle. How is this scale formed? What is its harm?
Sea water is a type of hard water and contains soluble salts. It cannot be used in boilers because of the following three main difficulties: (i) Formation of scales: The dissolved salts present in sea water deposit a hard crust (boiler scale) on the walls of the boiler. The crust is hard and heat insulating. It makes wastage of fuel. Sometimes the crust breaks at certain place which leads to an accident.
(ii) Corrosion : The chlorides of calcium and magnesium present in sea water upon boiling undergo hydrolysis to produce HCl.
HCl thus formed attacks the metal surface of the boiler and thereby shortens its life.
(iii) Foaming: It is the formation of bubbles on the surface of the water in the boiler. This occurs due to the presence of suspended particles in water. It causes wastage of fuels.
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