Question

Blue litmus paper is dipped in a solution. It remains blue, what is the nature of the solution? Explain.

Answer 1

 Hint: Litmus paper test is used to detect whether a given substance is acidic or basic. If a substance is acidic it would change the colour of blue litmus to red and if its basic it would change the colour of red litmus to blue. Also, if the substance is neutral it won’t change colour of either red or blue litmus paper.

Complete step by step answer:
 We know that litmus test is used to detect whether the given substance is an acid or a base. If we put a drop of acid on red as well as blue litmus paper, the colour of blue litmus will change to red and that of red litmus would remain the same. If we put a drop of a base on both red and blue litmus paper, the colour of red litmus would change to blue while that of blue litmus remains the same. If we put a drop of a neutral solution on litmus of both the colours, no colour change would be observed on either coloured paper.
In the given situation, the colour of blue litmus remains blue, so the solution must either be a base or a neutral solution.

Additional information: Red litmus contains a weak diprotic acid. When it is exposed to a basic compound, the hydrogen ions react with the added base. The conjugate base formed from the litmus acid has a blue colour, so the wet red litmus paper turns blue in alkaline solution.

Note:
To confirm the nature of the given solution, we can put a drop of it on red litmus paper. If the paper turns blue, the solution is basic in nature and if its colour remains unchanged, the solution is neutral in nature.