Several common problems of EDTA

Why is EDTA used in titration?

The most common indicator in complexometric titration is organic dye, whose function is to form a colored complex with the metal ions being titrated. During the reaction, EDTA replaces the indicator and forms a more stable complex with metal. When the reaction is completed, the color change can be observed.

What iron content can be titrated?

EDTA titrates the total iron in the mixture of iron (II) and iron (III).

What is EDTA titration?

EDTA is the abbreviation of EDTA, and EDTA titration is also known as EDTA titration. EDTA is a commonly used strong complexing agent. EDTA can form stable complexes with many metal ions. Based on the complexation reaction of EDTA and metal ions, the end point of titration is determined by the discoloration of metal indicators or electrical and optical methods, and the content of the measured substance is calculated according to the amount of standard solution. EDTA titration can directly or indirectly determine about 70 metal elements, and the most commonly used method is to determine the concentration of calcium and magnesium ions.

Why use EDTA titration at pH=10?

Because the stability constant of calcium magnesium plasma and EDTA is not large enough, it needs to be used for EDTA titration under weak alkaline conditions, namely pH=10 buffer solution.

Why is indicator not used in potassium permanganate titration?

Because potassium permanganate is a kind of dark purple, which is easy to see with the naked eye. When titrating it, the color will disappear, so there is no need for indicators to tell you the end point. Potassium permanganate is an oxidant, which is dark purple.

What is the role of ammonia buffer in EDTA titration?

Adjust the pH value of ammonia buffer solution in EDTA titration to ensure the completion of the reaction.

Note: complexometric titration uses the formation of colored complex to indicate the end point. EDTA, usually written as H4Y, is a common ligand in complexometric titration.

What is the pH value in EDTA titration?

The hardness is determined by titration with EDTA at a buffer pH of 10. Brucite is used as an indicator.

What is a buffer solution?

Buffer solution (specifically, pH buffer or hydrogen ion buffer) is an aqueous solution composed of a mixture of weak acids and their conjugated bases, and vice versa. When a small amount of strong acid or strong base is added, its pH value changes little.

How does EDTA play a role in the titration reaction?

In titration, EDTA is a stronger complexing agent than the indicator. It replaces the indicator with metal ions to return the indicator (through purple shadow) to pure blue, indicating the end of the reaction.

How to use the volume of EDTA in the experiment?

For example, nickel content in salt. In this experiment, the indicator used is uracil indicator. Its binding strength with nickel ions is lower than EDTA. Therefore, when the reaction is completed (all nickel is used up), the volume of EDTA used can be used to determine the concentration of metal ions.

Why is chrome black T red in EDTA?

Because chrome black T is the indicator of complexometric titration. When it forms a complex with metal ions (Ca2+, Mg2+...), it is red. When all metal ions are chelated by EDTA, it is blue, so you can determine the end point of titration.

Why can EDTA combine with metal ions?

The ability of EDTA to combine with metal ions is due to the lone pair of electrons in its structure, which enables it to chelate ions. This must be done under basic conditions so that H+will not be attracted by isolated pairs.