Methyl red (2-(N, N-dimethyl-4-aminophenyl) azobenzenecarboxylic acid), is an indicator dye commonly known as C.I. Acid Red 2. It is an azo molecule in which, unlike methyl orange, the sulfonic acid function has been replaced by the carboxylic acid function.
Methyl red (C15H15N3O2) is a weak acid that dissociates in water to form a red neutral molecule. It's an azo dye that comes in the form of a dark red crystalline powder and is used as a pH indicator. With a pKa of 5.1, it turns red below pH 4.4, yellow above pH 6.2, and orange in the neutral condition.
Frequently Asked Question (FAQ):
Is methyl red a synthetic or natural indicator?
The methyl red is a synthetic indicator, not a natural indicator. It can be prepared by the diazotization of anthranilic acid in an alcoholic solution.
Is methyl red soluble in water?
It is practically insoluble in water, soluble in ethanol and acetic acid.
Why is methyl red not soluble in water?
Because methyl red has a pKa of 4.95, it does not ionize in distilled water.
Why does methyl red turn red?
It shows red color below pH 4 as a structural change in methyl red causes the pH-dependent color change. When the dimethylamino group is protonated at pH 4.0-6.0, the predominant structural form is the quinone diamine form on the right.
At what pH does methyl red turn red?
Methyl red turns red when the pH drops below 4.4.
Is methyl red a universal indicator?
Methyl red is not a universal indicator, although it is a component of it. Phenolphthalein, thymol blue, methyl red, bromothymol blue, and are the major components of a universal indicator solution.
How do you make a methyl red indicator?
To make a methyl red indicator you will need to dissolve 50 mg of methyl red in 100 ml of ethanol, containing 04.00 ml of 0.05N NaOH solution.
Methyl red indicator is suitable for which titration?
Methyl red is suitable for acid titration due to its low pH range. It is also commonly used for the titration of a strong acid (Analyte) vs a strong base.
Why is methyl red used instead of methyl orange?
Methyl orange has a pH range of 3.1 to 4.4, while methyl red has a pH range of 4.4 to 6.2, and both will indicate changes on the pH scale.
Methyl Red is an azo-dye indicator that indicates the endpoint/equivalence point of the reaction (changes color) when the pH of the medium it's in about 4.4 to 6.2. For this reason, it is used as an indicator in acid-base titrations.
What does it mean when methyl red turns yellow?
This means that the pH of the solution is at basic conditions, it shows a yellow color above pH 6.2.
What is methyl red used for?
It is used as an indicator in the laboratory, used as a dye in leather products, textile products, and in some food products, used in microbiology for identifying bacteria, and also used in research, and for industrial purposes.
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