Question

Neutral litmus solution have _ _ _ _ _ _ _?
(A) No effect of acidic solution
(B) No effect of alkaline solution
(C) Both A and B
(D) None of these

Answer 1

Hint: A neutral litmus solution is a purple (or violet) coloured solution and has the ability to indicate the presence of both acid and base. It is a combination of many dyes mixed together.

Complete answer:
-Lichens are used to extract a water soluble mixture of different dyes which is known as litmus. When this solution is extracted onto filter papers they act as pH indicators and are used to check for acidity or basicity of any compound or solution.
-There are 3 types of litmus papers: neutral, blue and red litmus paper.
If a blue litmus paper is dipped in an acidic solution it turns red and it does not change colour in a basic medium.
If a red litmus paper is dipped in a basic solution or alkaline solution, it turns blue and does not change in an acidic solution.
The neutral litmus paper is purple in colour.
-We can prepare litmus solutions that function in the same manner as litmus papers. The solution is res when the conditions are acidic and it is blue when the conditions are basic or alkaline.
-If the neutral litmus solution is exposed to acidic conditions it turns its colour from purple (or violet) to red and under alkaline or basic conditions it turns blue. It consists of about 10 to 15 different dyes like leuc azolitmin, azolitmin, spaniolitmin and leucovorin.
-Litmus solutions are prepared by dissolving the above mentioned lichen based dyes in water of neutral pH and then we can observe the change in colour by adding compounds or substances of unknown pH.
Neutral solutions are more preferred in laboratories and industries nowadays because they can indicate the presence of both acids and bases by tuning its colour into red and blue respectively.

So, the correct option is: (D) none of these.

Note: When a red litmus paper is exposed to alkaline conditions it turns into blue because: red litmus paper contains a diprotic acid and releases hydrogen ions in interaction with a basic compound. Then the formation of its conjugate base causes the blue colour.