Hardness of drinking w ater should be?
Correct Answer: 3-Jan
Description: Ans. is 'c' i.e., 1-3 o Drinking water should be moderately hard (1-3 meq/Lit) Park 2la/ep. 672o Softening of water is recommended when the hardness exceeds 3meq/L (150 mg'L).Hardness of watero Hardness of water is defined as the soap-destroying power of water,o Water is considered to be bard if large amounts of soap are required to produce lather.o The hardness is caused by high mineral content, Mainly calcium and magnesium cations,o Hardness may be : -i) Temporary (Carbonate) hardness - Calcium bicarbonate & Magnesium bicarbonate.# It is called temporary because it can be removed by boiling or addition of lime.ii) Permanent (Non-Carbonate) hardness - Calcium Sulfate, magnesium sulfate, Calcium chloride, magnesium chloride# It is called permanent because it cannot be removed by boiling,o Hardness is expressed in terms of mili-equilents per litre (mEq/L).o One mEq/L of hardness - producing ion is equal to 50 mg CaCO3 (50ppm) in one litre of water.Classification of hardness in waterClassificationLevel of hardness (mEqjlitre)a) Soft waterb) Moderately hardc) Hard waterd) Very hard waterLess than 1 (< 50 mg/L)1-3(50- 150 mg/L)3-6(I50-300mg/L)Over 6 (> 300 mg/L)
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