Question

The hardness of a water sample (in terms of equivalents of CaCO₃ containing 10^-3 MCaSO₄ is 

(Molar mass of CaSO₄ = 136 g mol^-1)
1. 100 ppm
2. 10 ppm
3. 50 ppm
4. 90 ppm

Answer 1

Correct Answer - Option 1 : 100 ppm

Concept:

The hardness of the water sample can be calculated in terms of ppm concentration of CaCO₃

The hardness of water = ppm of CaCO₃

Calculation:

Given, molarity = 10^-3 M

i.e., 1000 mL of solution contains 10^-3 mole of CaCO₃

∴ The hardness of water = ppm of CaCO₃

\( = \frac{{{{10}^{ - 3}} \times 1000}}{{1000}} \times {10^6}\)

= 100 ppm.