Question

Hardness of water is expressed in terms of ppm of sodium carbonate.
If this is true enter 1, if false enter 0.

Answer 1

Hardness of water is expressed in terms of ppm of calcium carbonate.

The various alternative units represent an equivalent mass of calcium oxide $\left(CaO\right)$ or calcium carbonate $\left(CaC{O}_3\right)$ that, when dissolved in a unit volume of pure water, would result in the same total molar concentration of $M{g}^{2+}$ and $C{a}^{2+}$. The different conversion factors arise from the fact that equivalent masses of calcium oxide and calcium carbonates differ, and that different mass and volume units are used. Parts per million (ppm) is usually defined as 1 mg/L $CaC{O}_3$. It is equivalent to mg/L without chemical compound specified.