Multiple choice

Results of a water sample analysis are as follows:

Cation Concentration (mg/I) Equivalent Weight
Na+ 40 23
Mg+2 10 12.2
Ca+2 55 20
–K+ 2 39

(milliequivalent weight of CaCO3 = 50 mg/meq). Hardness of the water sample in mg/l as CaCO3 is

  1. 44.8

  2. 89.5

  3. 179

  4. 358
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C Correct answer
Explanation

Hardness as CaCO3 is calculated by converting the concentration of divalent cations (Mg2+ and Ca2+) to meq/l and then multiplying by the equivalent weight of CaCO3 (50). (10/12.2 + 55/20) * 50 = 179 mg/l.

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