Q41GATE 2003MCQ

Zero hardness of water is achieved by

Q42GATE 2003MCQ

The results of analysis of raw water sample are given below : Turbidity : 5 mg/L pH : 7.4 Fluorides : 2.5 mg/L Total Hardness : 300 mg/L Iron : 3.0 mg/L MPN : 50 per 100 mL From the data given above, it can be inferred that water needs removal of

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Q43GATE 2002MCQ

In natural water, hardness is mainly caused by

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📖 Explanation

Hardness in water is due to multivalent metallic cations and is mainly due to $Ca^{++}$ and $mg^{++}$ because these are most commonly present in water.

Q44GATE 2001MCQ

The $Ca^{2+}$ concentration and $Mg^{2+}$ concentration of a water sample are 160 mg/lit and 40 mg/lit as their ions respectively. The total hardness of this water sample in terms of $CaCO_3$ in mg/lit is approximately equal to

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📖 Explanation

Total hardness

\begin{aligned} &=Ca^{+}\: mg/l\left ( \frac{50}{20} \right )+Mg^{+}\: mg/l\times \left ( \frac{50}{12} \right ) \\ &=160\times \frac{50}{20}+40\times \frac{50}{12} \\ &=566.67\: mg/l \end{aligned}