Question

How is a universal indicator obtained? How is the wide range of pH of solution tested by it?

Hint:

Universal indicator = Mixture of indicators. Colour change + pH chart → Determine pH (0–14).

Answer 1

How is a Universal Indicator Obtained?

A universal indicator is prepared by mixing several different indicators together in suitable proportions. It is a mixture of indicators such as: – Methyl red
– Phenolphthalein
– Bromothymol blue
– Thymol blue Each indicator shows a colour change at a particular pH range. When combined, they produce a solution that shows different colours over a wide range of pH values (from pH 1 to pH 14).

How is the Wide Range of pH Tested by It?

When a few drops of universal indicator are added to a solution: – The solution changes colour depending on its pH value.
– The colour obtained is compared with a standard pH colour chart.
– Each colour corresponds to a specific pH value. For example: – Red indicates strongly acidic solution (low pH).
– Yellow indicates weakly acidic solution.
– Green indicates neutral solution (pH 7).
– Blue indicates weakly basic solution.
– Violet or purple indicates strongly basic solution (high pH). Because it gives different colours across the entire pH scale, it can test a wide range of acidity and basicity.

Conclusion:
A universal indicator is obtained by mixing several indicators together. It tests a wide range of pH values by showing different colours for different levels of acidity or basicity.