The correct answer is D. Non carbonate hardness.
Hardness in water is caused by the presence of dissolved minerals, such as calcium and magnesium. These minerals can come from the natural environment, such as rocks and soil, or from human activities, such as agriculture and industry.
There are two types of hardness in water: carbonate hardness and non-carbonate hardness. Carbonate hardness is caused by the presence of bicarbonate ions, which are formed when carbon dioxide dissolves in water. Non-carbonate hardness is caused by the presence of other minerals, such as calcium sulfate and magnesium chloride.
The total hardness of water is the sum of the carbonate and non-carbonate hardness. The total alkalinity of water is the measure of the ability of water to resist changes in pH.
If the total hardness of water is greater than its total alkalinity, then the carbonate hardness will be equal to the non-carbonate hardness. This is because the carbonate hardness is the only type of hardness that contributes to the total alkalinity.
Here is a brief explanation of each option:
- Option A: Total alkalinity. This is the measure of the ability of water to resist changes in pH. It is caused by the presence of bicarbonate ions, which are formed when carbon dioxide dissolves in water.
- Option B: Total hardness. This is the sum of the carbonate and non-carbonate hardness. It is caused by the presence of calcium and magnesium ions, which can come from the natural environment, such as rocks and soil, or from human activities, such as agriculture and industry.
- Option C: Total hardness total alkalinity. This is not a valid option.
- Option D: Non carbonate hardness. This is the type of hardness in water that is not caused by the presence of bicarbonate ions. It is caused by the presence of other minerals, such as calcium sulfate and magnesium chloride.