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 $\mathrm{CaCO}_3$ is (molar mass of calcium bicarbonate is $162 \mathrm{~g} \mathrm{~mol}^{-1}$ and maanesium bicarbonate is $146 \mathrm{a} \mathrm{mol}^{-1}$ )
Select the correct option:
A
5,000 ppm
B
100 ppm
C
10,000 ppm
D
1,000 ppm
✓ Correct! Well done.
✗ Incorrect. Try again or view the solution.
Solution
Moles of $\mathrm{Ca}\left(\mathrm{HCO}_3\right)_2=0.005$
Moles of $\mathrm{Mg}\left(\mathrm{HCO}_3\right)_2=0.005$
Hardness in terms of $\mathrm{CaCO}_3$ pm
$$
\begin{aligned}
& =\frac{(0.005+0.005) \times 100}{100} \times 10^6 \\
& =10^4 \mathrm{ppm}
\end{aligned}
$$
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