How many pKa values does EDTA have?

The pKa values of free EDTA are 0, 1.5, 2 and 2.66 (deprotonation of the four carboxyl groups) as well as 6.16 and 10.24 (deprotonation of the two amino groups). Due to its complexing property there is a broad applicability for EDTA as preservatives in food or cosmetic products.

How many carboxylic acid groups are present in EDTA?

Ethylenediamine tetraacetic acid (EDTA) is a polyprotic acid containing four carboxylic acid groups and two amine groups with lone-pair electrons that chelate calcium and several other metal ions.

Is EDTA a carboxylic acid?

Ethylenediaminetetraacetic acid (EDTA) is a chelating agent can bind to metals via four carboxylate and two amine groups. It is a polyamino carboxylic acid and a colorless, water-soluble solid, which is widely used to dissolve lime scale.

How many acidic protons are in EDTA?

EDTA is a hexaprotic acid – it has 6 acidic hydrogens. EDTA has four carboxylic acid groups and two amino groups (see structure below), so the fully protonated form has an overall 2+ charge.

What factors influence EDTA titration?

FACTORS AFFECTING THE TITRATION VALUES Nature of the metal ion: When the acidity of the metal ion increases, the complex stability also increases. Ionic size: The smallest ion forms the stable complex. Ionic charge: The higher charge forms the more stable complex is.

What is Ka of EDTA?

Ethylenediaminetetraacetic acid (also called ethylenedinitrilotetraacetic acid), which is commonly shortened to EDTA, has the structure: The dissociation constants for the four carboxylic acid groups are: K1 = 1.02·10-2, K2 = 2.14·10-3, K3 = 6.92·10-7 and K4 = 5.50·10-11.

How many acidic hydrogens does EDTA?

Why pH is controlled in EDTA titrations?

Effect of pH: During a complexometric titration, the pH must be constant by use of a buffer solution. Control of pH is important since the H+ ion plays an important role in chelation. Most ligands are basic and bind to H+ ions throughout a wide range of pH.

How many acidic protons does EDTA have?

The EDTA Molecule It is a polyprotic acid containing four carboxylic acid groups (acidic hydrogens are red) and two amine groups with lone pair electrons (green dots).

Why is EDTA pH-dependent?

Pure ethylenediaminetetraacetic acid tetrasodium salt (EDTA. Na4) in water showed a pH-dependent change of optical density detected in the ultraviolet region. The most important change was found between pH 4 and 8, corresponding to the deprotonation of the third ionizable group having a pK of 6.2.