Question

Which of the chemicals used to soften hard water?

Answer 1

Hint: Softening is the process of removing the dissolved magnesium and calcium salts which cause water hardness. Chemicals like sodium carbonate $(N{a_2}C{O_3})$, slaked lime $(Ca{(OH)_2})$, Sodium chloride $(NaCl)$.

Complete step-by-step answer:
Water softening is the removal of dissolved calcium and magnesium salts which causes water hardness. Like hard water, softened water does not build an insoluble scale or precipitate in pipes and reservoirs, or mess with cleaners like soap. Water softening is also necessary in many sectors, and in a number of countries small water softening devices are being used in homes.
Hard water may be troublesome because calcium and magnesium ions combine with soap's higher fatty acids to create an insoluble gelatinous curd, resulting in soap waste. In boilers, the hard waters of calcium and magnesium form a strong adherent scale on the plates. As a result of the scale's low heat conductivity, fuel consumption is increased, and the boiler quickly deteriorates as the plates become overheated externally. Sodium carbonate, if present, hydrolyses to create free alkali causing caustic fragility and boiler plate failure.
Water softening is accomplished either by adding insoluble precipitates to chemicals, or by exchanging ions. Chemicals used for softening on a small scale include ammonia, borax, calcium hydroxide, or trisodium phosphate, usually in conjunction with sodium carbonate. To extract the precipitates, the lime-soda water softening process has to be accompanied by sedimentation and filtration.

Note: - For answering these types of questions we must understand the property of hard water and also the chemicals used for softening the hard water. In industries hard water cannot be used because it damages the quality of appliances being used. Hence, we can see that softening of hard water is an important activity.