EDTA ethylenediaminetetraacetic acid is the most widely used

EDTA (ethylenediaminetetraacetic acid) is the most widely used metal chelator in analytical chemistry, which forms strong 1:1 complexes with most metal ions. Water hardness can be determined by titrating Ca²⁺, Mg²⁺ and other metal ions with EDTA. During the titration, ammonium-ammonium chloride buffer is often used.

Which of the following descriptions about the function of ammonium-ammonium chloride is/are correct?

A) To form complex with Ca²⁺ and Mg^{2+ (Correct or incorrect)}

^B) To act as a masking agent (Correct or Incorrect)

C)To minimize the affect of other metal ions (Correct or incorrect)

D) To be used as a metal ion indicator (Correct or incorrect)

Solution

Ammonia is a ligand tat binds themetal ions strongly enough to prevent metal hydroxides from precipitating but weakly enough to give up the metal when EDTA is added.

Therefore,

A) To form complex with Ca²⁺ and Mg²⁺ : Correct

B) To act as a masking agent: Correct

C) To minimize the affect of other metal ions: Incorrect

D) To be used as a metal ion indicator: Incorrect