Question

What happens when Red litmus paper is dipped in a beaker containing dilute \[NaOH\] ?

Answer 1

Hint: Light Blue litmus paper turns into red colour under acidic conditions and red litmus paper will turn blue under basic or alkaline conditions, with the colour change occurring over the pH range 4.5–8.3 at room temperature. Neutral litmus paper is usually purple in colour.
We also know that \[NaOH\] is a base and usually provides alkaline conditions for a solution.

Complete answer:
Litmus paper is a filter paper which has been treated with a natural water-soluble dye obtained from a symbiotic species of fungus and algae called lichens. Litmus paper can be used as a pH indicator. Neutral litmus paper is a shade of purple in colour. Neutral litmus paper turns red under acidic conditions and will turn blue under alkaline conditions.
A Dilute solution of Sodium hydroxide will be basic in nature. We know that blue litmus paper when introduced to a base will not undergo any changes. But when red litmus paper is introduced in a basic solution, the colour of the litmus paper will change from red to blue. Red litmus paper contains a weak diprotic acid. Upon exposure to the base, hydrogen ions from the acid react with the base which will produce a blue colour.

Note:
Wet litmus paper can be used to test for water-soluble gases like carbon dioxide that affects acidity or basicity. The gas dissolves in the water and the resulting solution will produce a colour change in the litmus paper. For example ammonia gas, which is alkaline, turns red litmus paper blue.