What is carbon dioxide used for in the process of lime softening?

• A. To remove toxins
• B. To correct pH and stabilize water
• C. To deodorize the water
• D. To enhance mineral content

Answer: (B)

In the process of lime softening, carbon dioxide plays a crucial role in correcting pH and stabilizing water. Lime softening is primarily used to reduce hardness in water by converting dissolved calcium and magnesium salts into insoluble forms that can be removed. When lime (calcium hydroxide) is added to water, it raises the pH, which can lead to the precipitation of hardness-causing minerals.

Adding carbon dioxide to the system helps to regulate and lower the pH after lime is introduced. This adjustment ensures that the water remains within an optimal pH range for stability and the effective removal of hardness. By dissolving some of the lime back into its soluble form when carbon dioxide is introduced, it helps create a balanced environment where dissolved calcium and magnesium can precipitate out effectively, thus improving the overall stability of the treated water.

The other options do not accurately reflect the role that carbon dioxide plays in lime softening. It is not primarily used to remove toxins or deodorize water, nor does it enhance mineral content, which positions the correct answer as the most relevant in the context of its function in the lime softening process.