The degree of hardness of water is usually expressed in terms of

Options

A. ppm by weight of `MgSO_4`
B. g/L of `CaCO_3` and `MgCO_3` present
C. ppm by weight of `CaCO_3` irrespective of whether it is actually present
D. ppm of `CaCO_3` actually present is water

Answer

C

Explanation

Degree of hardness is the number of parts of `CaCO_3` equivalent to various calcium and magnesium salts present in a million parts of water by mass (ppm).