A compound that changes color when exposed to acidic or basic conditions is called an indicator. Color indicators are widely used to detect pH and can be added to reaction mixtures to determine titration endpoint/equivalence point.
In chemistry, different indicators are used in several types of titration, including acid-base, precipitation, redox, and complexometric. Each has its own pH range, pKa, and produces a specific color at different pH values. The two theories that explain the acid-base indicator are Ostwald's theory and the quinonoid theory.
What is methyl yellow?
Methyl yellow (4-dimethylaminoazobenzene-C6H5N2C6H4N (CH3)2 is an organic compound that an azo dye derived from dimethylaniline generally used as an acid-base indicator. It comes in yellow solid powder whose solubility in water is 13.6 mg/l; it is also soluble in ethanol, acetone, chloroform, ether, etc.
The pH range of dimethyl yellow is 2.9 to 4.0, and in an aqueous solution, it changes color from below pH 2.9 red to above pH 4.0 yellow and vice versa. Methyl orange, methyl red, are also types of indicators used in the titration.
Methyl yellow is used as an acid-base indicator, typically employed to titrate a weak base against a strong acid. It is a part of a universal indicator and is also used as a dye for plastics.
Properties of Methyl yellow: | |
|---|---|
| Molecular Weight/ Molar Mass | 225.295 g•mol−1 |
| Formula | C14H15N3 |
| Density | 1.0±0.1 g/cm3 |
| Appearance | Yellow crystals |
| Melting point | 11–116 °C |
| pKa | 3.3 |
| pH range | 2.9 to 4.0 |
| Color in acid | Red |
| Color in base | Yellow |
FAQ (Frequently Asked Questions):
What is the color of methyl yellow?
The solid methyl yellow that comes in the form of crystals is yellow in color.
What is the pH range of the methyl yellow indicator?
The transition interval of methyl yellow is pH 2.9 (red) to pH 4.0 (yellow).
What is the color of methyl yellow in an acidic and basic environment?
Methyl yellow undergoes a transition between pH 2.9 and 4.0, showing red in low pH and turning yellow above pH 4.0.
What is the color of methyl yellow in acid?
Methyl yellow is a pH indicator that turns red when exposed to acidic conditions.
What is the color of methyl yellow in the base?
Methyl yellow is a pH indicator that turns yellow when exposed to basic conditions.
How do you make a methyl yellow indicator?
To make the methyl yellow indicator needs to weigh 100 mg of dimethyl yellow and dissolve in 100 ml of ethanol.
Methyl yellow is used for which titration?
It is more suitable for titration of a weak base against a strong acid.
References:
- Wikipedia contributors. (2021, May 22). Methyl yellow. In Wikipedia, The Free Encyclopedia. Available Here:
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