Question

EDTA is used for the estimation of:

• A. Na${}^{+}$ and K${}^{+}$ ions
• B. Cl${}^{-}$ and Br${}^{-}$ ions
• C. Cu2${}^{2+}$ and Ag${}^{+}$ ions
• D. Ca${}^{2+}$ and Mg${}^{2+}$ ions

Answer 1

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

EDTA is used for the estimation of $C{a}^{2+}$ and $M{g}^{2+}$ ions.

EDTA has four carboxyl groups and two amine groups that can act as electron-pair donors or Lewis bases. The ability of EDTA to potentially donate its six lone pairs of electrons for the formation of coordinate covalent bonds to metal cations.

In alkaline conditions $(pH>9)$, it forms stable complexes with the alkaline earth metal ions $C{a}^{2+}$ and $M{g}^{2+}$. The EDTA reagent can be used to measure the total quantity of dissolved $C{a}^{2+}$ and $M{g}^{2+}$ ions in a water sample. Thus, the total hardness of a water sample can be estimated by titration with a standard solution of EDTA.