Is carbonate hardness classified as temporary or permanent?

Carbonate hardness, also known as temporary hardness, arises primarily from the presence of bicarbonate and carbonate ions in water. This type of hardness can be removed by boiling the water, which causes the bicarbonates to decompose into carbonate, allowing the precipitation of calcium and magnesium as insoluble carbonates.

When water is boiled, the bicarbonate ions convert to carbonates and precipitate out, effectively reducing the hardness. Because of this ability to be eliminated through physical treatment (boiling), carbonate hardness is categorized as temporary. In contrast, permanent hardness, caused by the presence of sulfate or chloride ions (such as in calcium sulfate), cannot be removed through boiling and requires chemical treatment methods like ion exchange or the addition of chemical softeners.

Thus, the classification of carbonate hardness as temporary is correct due to its reversible nature under certain conditions, allowing for its removal through simple methods.