What method is used for determining the hardness of water?

Titration with a chelating agent is the appropriate method for determining the hardness of water because it specifically measures the concentration of calcium and magnesium ions, which are the primary contributors to water hardness. In this method, a sample of water is treated with a chelating agent, such as EDTA (ethylenediaminetetraacetic acid), which binds to the calcium and magnesium ions. The point at which all of the hardness ions have reacted with the chelating agent is determined through a color change, often observed with an indicator. This allows for precise quantification of hardness.

Additionally, while spectroscopy can measure the concentration of ions in water, it is not the standard method for assessing hardness specifically. Filtration does not measure hardness but rather removes particulates from water. Boiling point analysis can show changes in water properties but isn’t a reliable metric for hardness, as it does not directly measure the concentration of hardness-related ions. Thus, titration with a chelating agent remains the standard and effective approach for this assessment.