Types of Hardness of Water

Permanent hardness can be removed through the following methods:

i. Distillation

Distillation removes both temporary and permanent hardness by evaporating the water and condensing the steam.

ii. Adding sodium carbonate (washing soda)

Washing soda reacts with calcium and magnesium compounds to form insoluble calcium carbonate, removing both types of hardness. The reaction is as follows:

CaSO4(aq) + Na2CO3(aq) → CaCO3(s) + Na2SO4(aq)

iii. Ion exchangers

Ion exchangers remove both types of hardness by replacing calcium (Ca²⁺) and magnesium (Mg²⁺) ions with sodium (Na⁺) ions. The process uses a container filled with ion exchange resin, which holds sodium ions weakly attached to it.

1. When hard water passes through the ion exchanger, calcium and magnesium ions attach to the resin, replacing the sodium ions.
2. The softened water leaves the ion exchanger with sodium ions instead of calcium and magnesium ions.
3. Over time, the resin becomes saturated with calcium and magnesium ions and must be regenerated by pouring a concentrated sodium chloride solution into the exchanger. This displaces the calcium and magnesium ions, making the resin reusable.

Water that lathers easily with soap is soft water, such as rainwater, distilled water, and boiled water. Hard water, such as seawater and some tap water, does not lather easily with soap.

Advantages

1. It tastes better due to dissolved minerals.
2. It provides calcium, essential for the growth of bones and teeth.
3. Limescale in pipes acts as insulation, preventing corrosion and stopping poisonous metal salts from dissolving into the water.

Disadvantages

1. Temporary hardness causes limescale buildup in boilers, kettles, and pipes, reducing efficiency and causing blockages.
2. Hard water requires more soap to form lather, leading to wastage.
3. Scum deposits from hard water are difficult to wash off and can damage various articles.