The hardness of a water sample

Question:

The hardness of a water sample (in terms of equivalents of $\left.\mathrm{CaCO}_{3}\right)$ containing $10^{-3} \mathrm{M} \mathrm{CaSO}_{4}$ is:

$\left(\right.$ molar mass of $\left.\mathrm{CaSO}_{4}=136 \mathrm{~g} \mathrm{~mol}^{-1}\right)$

  1. $100 \mathrm{ppm}$

  2. $50 \mathrm{ppm}$

  3. $10 \mathrm{ppm}$

  4. $90 \mathrm{ppm}$


Correct Option: 1

Solution:

ppm of $\mathrm{CaCO}_{3}$

$\left(10^{-3} \times 10^{3}\right) \times 100=100 \mathrm{ppm}$

 

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