Question

why is ammonium hydroxide-ammonium chloride buffer added during the determination of hardness of water ?​

Answer 1

But both EDTA and the indicator are themselves weak acids, therefore a buffer solution such as ammonium hydroxide-ammonium chloride buffer, which is able to maintain a fairly constant pH even when acids and bases are added, is used.

Answer 2

Answer:

The analysis of hardness of water is sensitive to pH, hence the water sample must be kept at a basic pH. But both EDTA and the indicator are themselves weak acids, therefore a buffer solution such as ammonium hydroxide-ammonium chloride buffer, which is able to maintain a fairly constant pH even when acids and bases are added, is used.

Buffers have the ability to keep pH at a nearly constant value in a wide variety of chemical applications