(1)Hard water is any water containing an appreciable quantity of dissolved minerals. (2) Some of the minerals come from chalk, limestone or marble, which the water may have flowed over or through. (4) Hard water contains calcium or magnesium ions. Limestone, marble or chalks are insoluble in pure water however they will dissolve slowly in acidic rain. If your water has emerged through limestone or chalk (calcium carbonate) it will be hard. (1) Soft water is gratification water in which the only cation (positively charged ion) is sodium. The minerals in water give it an idiosyncratic taste. Some natural mineral waters are highly desired for their flavour and the health benefits they may converse. (3) Extremely hard water affects plumbing such as pipes and the performance of certain cleaning agents. When the water is heated the carbonates precipitate out of solution, forming scale in pipes and kettles. (1) Calcium Hydrogen Carbonate and Magnesium Hydrogen Carbonate decompose when they are heated. The original insoluble carbonate is reformed. This happens when water is boiled.
Calcium Hydrogen Carbonate Carbon Dioxide + Water + Calcium Carbonate. Ca(HCO3)2(aq) CO2(g) + H2O(l) + CaCO3(s)
Magnesium Hydrogen Carbonate Carbon Dioxide + Water + Magnesium Carbonate Mg(HCO3)2(aq) CO2(g) + H2O(l) + MgCO3(s)
Boiling the water causes the precipitation of solid calcium carbonate or solid magnesium carbonate. This removes the calcium ions or magnesium ions from the water and so removes the hardness. Therefore, hardness due to Hydrogen Carbonates is said to be temporary. Calcium sulphate is slightly soluble in water when a river flows over Gypsum; it dissolves some of the rock. Therefore calcium gets into the water. How hard and soft water react with soap
(5)The cardinal disadvantage...