Question

Why is pH $10$ buffer used in EDTA solution?

Answer 1

To answer this question, you should know about the buffer solution. A buffer is the aqueous solution which consists of a mixture of weak acids or bases with their salts. The pH of the solution changes very little when acid or bases are added to it.

Complete answer:
Let’s first understand the complete definition of a buffer solution.
A buffer solution is the solution which has the stable concentration of hydrogen ions. They show a very little change in pH with the addition of acids and bases. In other words, we can say that buffer solutions almost remain constant. If the buffer solution contains the mixture of acids with its salts, it is called an acid buffer whereas if the solution contains a mixture of bases with its salts, it is called a base buffer. Buffer solutions are used to prevent the solution’s pH change.
Now, let’s know about the EDTA, ethylenediaminetetraacetic acids. It contains four carboxyl groups and two amine bunches which give its electron pair i.e. they act as Lewis bases. EDTA is widely used in complexometric titrations. The capacity of EDTA is to give six lone pairs of electrons for the formation of covalent bonds with metal cations and acts as a hexadentate ligand.
The pH $10$buffer used in EDTA solution so that EDTA reacts with the metal ions which are present in the titration solution which can be achieved by using a pH $10$ buffer.

Note:
The buffer solution is used in EDTA titration because it avoids the change in pH, so that reactions take place between metal ions and EDTA. Both the metal ions and EDTA are pH- dependent. Always remember that a buffer is added to the solution that undergoes titration in a specific pH range.