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GATE 2016 CE (CE2) – Question 60

Water and Waste Water Quality and Treatment · Water quality standards, parameters and water quality index · 2 marks · Multiple choice

The water-analysis bar diagram gives cumulative boundaries (meq/L): cations 0, 2.65, 4.10, 6.35, 6.85 for Ca²⁺, Mg²⁺, Na⁺, K⁺; anions 0, 3.30, 3.90, 6.75 for bicarbonate, sulfate, chloride. The non-carbonate hardness is ______ mg/L as CaCO₃.

  1. 40
  2. 165
  3. 195
  4. 205

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Correct answer: (A) 40

Explanation

The cation chart gives combined Ca and Mg concentration4.10meq/L, so total hardness is4.10·50=205mg/L as CaCO3. Bicarbonate alkalinity is3.30·50=165mg/L as CaCO3. Non-carbonate hardness is205−165=**40mg/L, A**. The chart’s total cations6.85 and anions6.75meq/L are slightly unbalanced, but the required hardness components are explicit.