100 mL of a water sample contains 0.81 g of calcium bicarbonate and 0.73 g of magnesium bicarbonate. The hardness of this water sample expressed in terms of equivalents of CaCO3 is:(Molar mass of calcium bicarbonate is 162 g mol–1 and magnesium bicarbonate is 146 g mol

Engineering

Chemistry

Hardness of Water and calculation

Question

100 mL of a water sample contains 0.81 g of calcium bicarbonate and 0.73 g of magnesium bicarbonate. The hardness of this water sample expressed in terms of equivalents of CaCO₃ is:

(Molar mass of calcium bicarbonate is 162 g mol^–1 and magnesium bicarbonate is 146 g mol^–1)

1,000 ppm

5,000 ppm

100 ppm

10,000 ppm

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n_eq. CaCO₃ = n_eqCa(HCO₃)₂ + n_eqMg(HCO₃)₂ (n_eq = Number of equivalent)

$or, \frac{W}{100} \times 2 = \frac{0 .81}{162} \times 2 + \frac{0 .73}{146} \times 2$

$∴$ w = 1.0

Volume of water = 100 mL

Mass of water = 100 g

$∴ Hardness = \frac{1 .0}{100} \times 10^{6} = 10000 ppm$