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Question:

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

10,000ppm

1000ppm

100ppm

5,000ppm

Solution:

Correct option is B. 10,000ppm
Solution:- (B) 10000 ppm
n_eq.CaCO3=n_eqCa(HCO3)2+n_eqMg(HCO3)2
or ,W/100 × 2 =0.81/162 × 2+0.73/146 × 2
∴ w=1.0
∴ Hardness=1.0/100 × 10⁶=10000ppm