Question

EDTA is used in the estimation of :

• A. ${Mg}^{2+}$ ions
• B. ${Ca}^{2+}$ ions
• C. Both ${Ca}^{2+}$ and ${Mg}^{2+}$ ions
• D. ${Mg}^{2+}$ ions but not ${Ca}^{2+}$ ions

Answer 1

The correct option is C Both ${Ca}^{2+}$ and ${Mg}^{2+}$ ions

Ethylenediaminetetraacetic acid (edta) is a reagent that forms edta-metal complexes with many metal ions (but not with alkali metal ions such as Na+ and K+). In alkaline conditions (pH9) it forms stable complexes with the alkaline earth metal ions Ca2+ and Mg2+. The edta reagent can be used to measure the total quantity of dissolved Ca2+ and Mg2+ ions in a water sample. Thus the total hardness of a water sample can be estimated by titration with a standard solution of edta.
Hence option C is correct