Ligand used in the estimation of hardness of water

Step-by-step solution

The hardness of water is due to the presence of Ca 2 + and Mg 2 + ions in it. The hexadentate ligand EDTA forms stable complexes with Ca 2 + and Mg 2 + ions and can be used for the estimation of hardness of water by simple titration method. Further, of Ca 2 + and Mg 2 + ions, each can be selectively estimated by this method because of the difference in the stability constants of their EDTA complexes.