Question

Why is methylene blue called a “redox indicator”? What does this term mean? Give the relevant chemical reaction for this experiment.

Answer 1

Methylene blue is widely used as a redox indicator in analytical chemistry, meaning that it indicates the presence or absence of oxygen. Oxygen-rich environments are said to be oxidizing. Some chemical elements, such as oxygen or chlorine, have such a strong attraction to electrons that they can strip electrons away from the atoms of other elements—these are known as oxidizing agents. Methylene blue indicates the presence of oxidizing agents because it is oxidized by these compounds. When electrons are stripped from methylene blue, the resulting molecule imparts a blue color to the solution—giving a clear sign of a chemical change.

Redox indicators are the chemicals used during the redox titration in order to detect the endpoint. In acid-base titrations, the indicators used were weak acids or bases which had two forms: dissociated (ionized) or non-ionized and both of these forms have a different color.

Similarly, the redox indicators have two forms: oxidized form and reduced form. In both the forms, the color is different. Both the form have a fixed potential.

In_ox+ne⁻→ In_red

Please provide the experiment detail for chemical reaction.