The major difference between them is that the methyl orange has a pH range of 3.1 (red) and 4.4 (yellow), while methyl red has a pH range of 4.4 (red) to 6.2 (yellow), they will both show a change in pH level at different points on the scale.
Methyl red and methyl orange both are used as an indicator in an acid-base titration, they both serve the same purpose, although the pH ranges are different.
What is methyl orange?
Methyl orange (C14H14N3NaO3S) is an organic dye composed of nitrogen, carbon, sulfur hydrogen, oxygen, and sodium. As of its distinct and diverse color variations at different pH levels, it is employed as a pH indicator in titrations.
Methyl orange is a weak acid that breaks down into orange neutral molecules when it comes in contact with water. Since it has a narrow range of sensitivity, it is not the same as a universal indicator like litmus paper. This implies that it can only be used to determine acidity in the pH range of 3.1 to 4.4.
What is methyl red?
Methyl red (C15H15N3O2), commonly known as C.I. Acid Red 2, is an indicator dye that becomes red in acidic solutions. It is an azo molecule with a structure that differs from methyl orange (Orange 3) in that the function of the sulphonic acid has been substituted by a carboxylic acid function.
Methyl red is a weak acid that dissociates in water to form red neutral molecules. It's an azo dye that comes in the form of a dark red crystalline powder that's used as a pH indicator. It's red at pH under 4.4, yellow at pH above 6.2, and orange in the middle, having a pKa of 5.1.
Difference between methyl red and methyl orange indicator:
- Methyl orange comes in the form of orange or yellow solid, while methyl red comes in the form of a dark red crystalline powder.
- Methyl orange is soluble in water (5 g/L) and ethanol (0.03 g/100 ml), while methyl red is soluble in ethanol (1mg/mL) and practically insoluble in water.
- Methyl orange indicator has a pH range of 3.1 and 4.4, while methyl red indicator has a pH range of 4.4 to 6.2.
- Methyl orange turns red below pH 3.1 and yellow above pH 4.4, while methyl red turns red below pH 4.4 and yellow above pH 6.2.
- Methyl orange has a pKa of 3.47 in water at 25 °C, while methyl red has a pKa of 5.1.
- Methyl orange is suitable for strong acid-weak base titration, while Methyl red is good for titration of strong acid (Analyte) with a strong base.
- The melting point of methyl orange is about > 300 °C, while the melting point of methyl red is 179–182 °C.
- The molar mass of methyl orange is 327.33 g·mol−1, while the molar mass of methyl red is 269.304 g·mol−1.
- The density of methyl orange is 1.28 g/cm3, while the density of methyl red is 0.791 g/cm3.
Frequently Asked Question (FAQ):
Are methyl red and methyl orange the same?
Methyl red and methyl orange is not the same thing, however, they are both used for the same thing (pH indicator) in different pH ranges.
What does it mean when methyl red turns orange?
The orange color is considered negative in the methyl red test, as there is less acid production in it.
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