Which of the following is a method of removing hardness from water?

• A. Chlorination
• B. Filtration
• C. Ion exchange
• D. Boiling

Answer: (C)

Ion exchange is a method specifically designed to remove hardness from water by replacing calcium and magnesium ions, which contribute to water hardness, with sodium or potassium ions. This process utilizes a resin that exchanges these ions, effectively softening the water. Ion exchange systems are commonly used in water treatment and household water softeners, enabling the production of soft water suitable for various applications, from industrial processes to household use.

In contrast, while chlorination is primarily used for disinfection purposes, filtration involves removing particulates or contaminants but does not specifically target hardness. Boiling can temporarily reduce hardness by precipitating some calcium and magnesium salts, but it is not an effective long-term solution for hardness removal as it does not change the ion composition in the water. Thus, ion exchange stands out as the most effective and targeted method for removing hardness.