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Universal Indicator

A universal indicator is a mixture of indicators that shows different colours for different pH values.

In one line: Universal indicator gives the colour map of pH.

Practice This Concept

Understand it

Universal indicator is useful when a student needs more information than simple litmus paper gives.
It can show whether a solution is strongly acidic, weakly acidic, neutral, weakly basic, or strongly basic.
The colour obtained can then be matched with a pH chart.
This makes it a powerful tool for comparing solutions in the laboratory.

Example

A neutral solution may show green, while a basic solution may show blue or purple depending on its pH.

Rule to remember

Universal indicator gives a colour pattern across the pH scale, helping estimate whether a solution is acidic, neutral, or basic.

See it worked out

Follow the example line by line, then use the same method on new questions.

Worked example

1A sample turns universal indicator green.
2From the chart, green indicates a neutral solution, so the sample is close to pH 7.

Method you can reuse

1First note the colour shown by the indicator.
2Next match it with the pH chart.
3Then state whether the solution is acidic, neutral, or basic and how strong it may be.

Visual tip

A colour strip chart from red through green to purple is the best support for this concept.

Check yourself

Answer the question in your head before opening the answer.

Try it yourself

Why is universal indicator better than litmus when comparing three unknown solutions?

Think first, then show answer

It is better because it gives different colours for different pH values, so it helps compare how acidic or basic the solutions are, not just whether they are acid or base.

Common wrong answer

A common wrong answer is to treat universal indicator like litmus and say it only shows acid or base. That misses the pH detail.

Don't mix this up

Students often confuse universal indicator with litmus. Litmus only tells acid or base, while universal indicator gives a pH range by colour.

Exam tip

If the question asks for exact comparison of strength, universal indicator is usually the better choice than litmus.

Write it in the exam

Each point is worth about one mark. Write point 1 for a 1-mark question and keep adding points as the marks go up.

How CBSE asks it

Questions often ask which indicator gives a pH range, what colour appears at a given pH, or how to compare unknown samples using colour charts.

1
Enough for 1 mark
A universal indicator is a mixture of indicators that shows different colours for different pH values.
2
Add for 2 marks
Example: A neutral solution may show green, while a basic solution may show blue or purple depending on its pH.
3
Add for 3 marks
It can show whether a solution is strongly acidic, weakly acidic, neutral, weakly basic, or strongly basic.

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