The hardness of water is a measurement of how acidic it is. true or false

The hardness of the water is given by the presence of calcium and magnesium carbonates. The mixing of these minerals in water turns the water more alkaline.

The Langelier saturation index uses the pH to predict the calcium carbonate stability of water. So, through the pH, it is possible to know whether a water is more or less acidic.

That is true. The lower the pH level, the more acidic it will be.