What Are Universal Indicators?

Hi,

Universal indicator is a mixture of indicators which exhibit different colour change in the pH range of 1–14.

For example: A strong acid (HCl or H2SO4 or HNO3) will have a pH of 1 and the colour red will be seen with universal indicator.
A weak acid will have a pH of 3 to 4 and orange will be seen with universal indicator.
The colour changes in universal indicator at different pH values are shown as:

Hope this answers your question.

Cheers!

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A universal indicator is typically composed of water, propan-1-ol, phenolphthalein sodium salt, sodium hydroxide, methyl red, bromothymol blue monosodium salt, and thymol blue monosodium salt ^[4]

The colours that indicate the pH of a solution, after adding a universal indicator are:

pH range	Description	Colour
0-3	Strong acid	Red
3-6	Acid	Orange/Yellow
7	Neutral	Green
8-11	Base	Blue
11-14	Strong Base	Purple