Chapter 12, Problem 44E

Interpretation Introduction

Interpretation:

The hardness of the given sample of water in ppm is to be calculated, and the water is to be classified.

Concept Introduction:

Solutions are homogeneous mixtures made up of two components, the solute and the solvent.

The same solutes and solvents can form a number of combinations by varying their amounts. These combinations can be differentiated in terms of concentration of solutions. Concentration of a solution is defined as the amount of solute present in the given amount of solvent.

Hard water is a solution of calcium and magnesium salts in water. The presence of calcium and magnesium ions makes water hard and renders it unusable for various purposes, such as cleaning clothes and utensils, bathing and in water heaters etc.

Hardness is usually expressed in terms of the presence of ${\text{CaCO}}_{\text{3}}$ with units as parts per million (ppm), which is defined as the mass of ${\text{CaCO}}_{\text{3}}$ present in ${10}^6$ g of a solution.

$\text{Hardness (ppm) = }\frac{{\text{Mass of CaCO}}_{\text{3}}}{\text{Mass of water sample}}\times {10}^6\text{ ppm}$ …..(1)