Question

A water sample contains CaSO4 80 ppm and MgSO4 100 ppm. The total hardness of water in ppm is​

Answer 1

Total hardness of water sample comes out to be 142 ppm

Explanation:

Since, both the constituents contribute in the permanent hardness of water and we are not given any information regarding other salts causing temporary hardness. So, we assume that there is only permanent hardness in this particular sample.

Permanent hardness = total hardness = Hardness dues to CaSo4 + Hardness dues to MgSo4

To convert to hardness as CaCO3 = mass of specie / molar mass * molar mass of CaCO3

For MgSO4

= 100 / 120 * 100 = 83.3 ppm or mg/l

For CaSO4

= 80/ 136 * 100 = 58.8 ppm or mg/l

Thus,

Total hardness = 83.3 + 58.5 = 142 ppm