Given total alkalinity of 114 mg/l and total hardness of 115 mg/l, what is the amount of permanent hardness?

To determine the amount of permanent hardness, it's important to understand the concepts of total hardness and total alkalinity. Total hardness primarily consists of both temporary hardness and permanent hardness. Temporary hardness is largely caused by the presence of bicarbonate ions (HCO3-), which can be neutralized by boiling the water, while permanent hardness is caused by other ions, such as calcium and magnesium sulfate or chloride, which remain even after boiling.

Given the total alkalinity of 114 mg/l, this indicates the presence of bicarbonates in the water, contributing to the temporary hardness. Since total hardness is 115 mg/l and consists of both temporary and permanent components, the difference between total hardness and total alkalinity provides the value for permanent hardness.

In this case, total hardness (115 mg/l) minus total alkalinity (114 mg/l) equals 1 mg/l of permanent hardness. This means the amount of hardness that cannot be removed by conventional methods, like boiling, is very small – just 1 mg/l. Therefore, the correct answer reflects this calculation, identifying the permanent hardness as 1 mg/l.