True

Explanation:

Carbonate hardness:
Carbonate hardness, also known as temporary hardness, is a measure of the concentration of bicarbonate and carbonate ions in water. It is caused by the presence of dissolved calcium and magnesium bicarbonate salts. Carbonate hardness can contribute to scale formation and can affect the performance of water-using equipment.

Removing carbonate hardness:
One method of removing carbonate hardness from water is by adding lime, which is calcium oxide (CaO), to the water. Lime reacts with the bicarbonate ions present in the water to produce insoluble calcium carbonate (CaCO3), which can then be removed through filtration or settling.

Chemical reaction:
The chemical reaction between lime and bicarbonate ions can be represented as follows:

CaO + H2O + CO2 → Ca(HCO3)2

Ca(HCO3)2 → CaCO3 + H2O + CO2

The first reaction involves the formation of calcium bicarbonate, which is soluble in water. The second reaction is the precipitation of calcium carbonate, which is insoluble and can be removed.

Effectiveness of lime:
The addition of lime to water can effectively remove carbonate hardness. Lime reacts readily with bicarbonate ions, causing them to convert into calcium carbonate. The calcium carbonate then precipitates out of the water, resulting in a decrease in carbonate hardness.

Other methods:
Apart from adding lime, there are other methods to remove carbonate hardness from water, such as ion exchange, reverse osmosis, and distillation. These methods can also effectively reduce or eliminate carbonate hardness depending on the specific conditions and requirements. However, adding lime is a common and cost-effective method used in various industrial and municipal water treatment processes.

Conclusion:
In conclusion, the statement is true. Carbonate hardness can be removed by adding lime to water. Lime reacts with bicarbonate ions to form insoluble calcium carbonate, which can then be removed from the water. This method is widely used and effective in reducing carbonate hardness.