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  4. 100 mL of a water sample contains 0.81 g of calcium bicarbonate and 0.73 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)

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Q. $100 \,mL$ of a water sample contains $0.81\, g$ of calcium bicarbonate and $0.73$ of magnesium bicarbonate. The hardness of this water sample expressed in terms of equivalents of $CaCO_3$ is: (molar mass of calcium bicarbonate is $162 \,g\, mol^{-1}$ and magnesium bicarbonate is $146\, g\,mol^{-1}$)

JEE MainJEE Main 2019Hydrogen

Solution:

$n_{eq} . CaCO_3 = n_{eq} Ca(HCO_3)_2 + n_{eq}MG(HCO_3)_2$
or $\frac{W}{100} \times2 = \frac{0.81}{162} \times2 + \frac{0.73}{146} \times2$
$ \therefore w = 1.0 $
$\therefore $ Hardness $ = \frac{1.0}{100} \times 10^{6} = 10000\, ppm$