The major difference between internal and external indicators is that the internal indicators are indicators in which one of the reactants acts as an indicator, whereas an external indicator is a type of indicator that is added externally and does not exist in the reactants.
Compounds that change color when exposed to acidic or alkaline solutions are known as indicators. Colored indicators are widely used to detect pH and can be added to the reaction mixture to determine the titration's endpoint or equivalence point. Although they can all be used to detect pH, they are not all suitable for the same application.
Hence the different types of indicators such as universal indicator, blue or red litmus paper, pH paper (pH 0.0 - 14), phenolphthalein (pH 8.2 - 10.0), methyl orange (pH 3.2-4.4), and bromothymol blue (pH 6.0-7.6), thymol blue (pH 8.0 - 9.6), etc. are used according to the pH range of the analyte.
| Table of Contents: What is an internal indicator? Example of internal indicator What is an external indicator Example of external indicator What is a self indicator? |
Indicators are classified based on how they behave when they react with acids and bases. They are classified into three categories: internal indicator, external indicator, and a self indicator which are discussed below.
What is an internal indicator?
In chemistry, an internal indicator refers to the indicator that acts as a reactant in the reaction. These are the indicators that take part in the reaction of the titration and change the color of the solution after the titration is completed, showing the sharp endpoint. Internal indicators are commonly employed in redox titrations.
What is the example of internal indicator?
Potassium permanganate is an example of an internal and self indicator that is generally used in redox titrations. KMnO4 is a potent and adaptable oxidant that can be used to detect a wide range of compounds by obvious or indirect titration.
What is an external indicator?
In chemistry, external indicators are those that are added externally to a chemical process that does not act as reactants. The indicators are usually colorless, but as the pH changes, they become colored. As the solution approaches the endpoint, the color change occurs. These types are avoided as they reduce the volume of the reaction mixture. In acid-base titrations, they are used as an indicator to detect pH changes.
What is the example of external indicator?
Methyl orange, phenolphthalein, and potassium ferricyanide are examples of external indicators. In acid-base titrations, phenolphthalein is often used as a pH indicator. It becomes colorless in acidic solutions and pink in basic solutions.
What is a self indicator?
Self indicators are not indicators; they are simply reactive species of titration (titrant or titrand) that act as indicators by changing the color of the sample solution itself and indicating the endpoint. The only indicator that participates in a chemical reaction is the internal indicator. After the titration is completed, the color of the solution becomes translucent; however adding one more drop of KMnO4 changes the color to light pink, marking the titration's endpoint.
What is external internal and self indicator?
An external indicator is one that is added during the titration process by taking a drop of the titration mixture externally and detecting the change in pH. e.g. phenolphthalein used in acid-base titrations. The self indicator is the only reactive species of the titration that acts as an indicator by changing the color of the sample solution and indicating the endpoint. E.g. potassium permanganate works as a self-indicator.
Diphenylamine is which type of indicator?
Diphenylamine is used as an internal indicator to estimate the strength of given Mohr’s salt solution by titrating against potassium dichromate solution. Because it shows a clear color change from green to violet when the endpoint of the titration is reached, diphenylamine is used as an indicator.
You may also like this
No comments:
Post a Comment