Question

Which of the following substances cannot change the colour of an indicator?
A.Acidic
B.Neutral
C.Basic
D.Dilute

Answer 1

Hint:The substance which has a pH less than 7 can change the colour of an indicator from blue to red.
The substance which has pH equal to 7 cannot change the colour of an indicator.
The substance which has pH more than 7 can change the colour of an indicator from red to blue.

Complete step by step answer:
The range of pH scale is from 0 to 14. The pH scale is used to tell the acidity, basicity and neutrality of the substance.
Acidic Substances: Acidic substances are those substances which can turn blue litmus to red. When the value of pH scale for a substance is less than 7 then, the substance is referred to as the acidic solution. These are those substances which can donate ${H^ + }$ ions. So, these substances can turn the colour of an indicator. For example – Hydrochloric acid, sulphuric acid etc.
Basic Substances: These substances can turn the colour of red litmus to blue litmus. The basic substances can be defined as the substances which have a value of pH in pH scale more than 7. The basic substances can also be called as alkaline substances. These substances contain $O{H^ - }$ ions. The examples of basic substances are calcium hydroxide, ammonia etc.
Neutral Substances: The substances which have the value of pH scale equal to 7 are termed as neutral substances. So, these substances cannot change the colour of any indicator. They cannot harm anyone. So, these are the substances which cannot change the colour of any indicator.
Hence, the correct option is (B).

Note:When the acid is strong, nearly all acid molecules can form ions and when the acid is weak, then only some molecules can form ions.
When the $O{H^ - }$ ions are more than the pH number is high.