Question

The main component of a universal indicator, in the form of a solution:
(A)- Phenolphthalein
(B)- Thymol blue
(C)- Methyl red
(D)- All of these

Answer 1

Hint: A solution that is sensible over a wide range of pH values and indicates the acidity and alkalinity of the solutions are known as a universal indicator.

Complete step by step answer:
-A substance that changes in different pH environments is known as an indicator. The indicator indicates whether a solution is acidic or basic.
-A mixture of all indicators which shows the pH values, the nature as well as the color of the pH of a particular solution is known as a Universal indicator.
-pH scale is a scale from 0 to 14 in which the values 0 to 6 correspond to acids, 8 to 14 corresponds to bases and pH 7 is for neutral solutions. Lesser the pH value for acid, the stronger is the acid. Lesser the pH value for basic, the weaker the base.

-There are three types of indicators present,
(i) Natural indicator- These are obtained naturally as extracts from nature. For example, litmus paper, china rose.
(ii) Synthetic indicator- These are formed chemically. For example, methyl orange, phenolphthalein.
(iii) Olfactory indicator- These are the indicators that change the smell of the indicator to show the nature of the solution. For example, vanilla, clove, onion.
-A universal indicator is mostly composed of water, 1-propanol, phenolphthalein, sodium salt, sodium hydroxide, methyl red, bromothymol blue, monosodium salt, and thymol blue salt.
So, the correct answer is “Option D”.

Note: The color changes of the universal indicator for different solutions are-
(i) For pH range up to 3, that is a strong acid, the universal indicator shows red color.
(ii) For pH range from 3 to 6, that is a weak acid, the universal indicator shows orange or yellow color.
(iii) For pH range 7, that is a neutral solution, the universal indicator shows green color.
(iv) For pH range from 8 to 11, that is weak alkali, the universal indicator shows a blue color.
(v) For pH range 11 to 14, that is a strong alkali, the universal indicator shows violet or indigo color.