What is the key purpose of using lime in the softening process?

The key purpose of using lime in the softening process is to precipitate hardness ions. In the context of water treatment, hardness is primarily due to the presence of calcium and magnesium ions. When lime (calcium hydroxide) is added to water, it reacts with these hardness ions to form insoluble compounds, primarily calcium carbonate, which can then be removed from the water. This precipitation process effectively reduces the concentration of hardness ions, ultimately leading to softer water.

While lime has other beneficial effects, such as neutralizing acidity, its main role in the softening process centers on the targeted removal of hardness ions, making it a crucial chemical in the treatment of drinking water. Additionally, the use of lime helps in achieving the desired water quality by addressing specific issues related to hardness that can affect both the taste and usability of water.