Question

Show wet blue and red litmus papers over the watch glass one by one. Which litmus paper shows a color change?

Answer 1

Hint : Litmus is a water-soluble mixture of different dyes extracted from lichens. It is often absorbed onto filter paper to produce one of the oldest forms of pH indicator, used to test materials for acidity. The main use of litmus is to test whether a solution is acidic or basic.

Complete Step By Step Answer:
When red litmus paper is placed into a basic substance, it will turn blue. If it comes in contact with an acidic or neutral substance, it will remain red. Red litmus paper is meant to test only for an alkaline $pH$level.
When blue litmus paper is placed in a substance that is acidic, it will turn to red. However, if placed in a substance that is basic or neutral, it will remain blue. Blue litmus paper is meant to test only for an acidic $pH$level.
Alkaline, or basic, substances are those that have a high hydrogen potential, meaning that they will readily bind with hydrogen molecules. Anything with $pH$ of more than $7$is basic.
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 color, so the wet red litmus paper turns blue in alkaline solution.

Note :
The litmus mixture has the CAS number and contains $10$ to $15$ different dyes. All of the chemical components of litmus are likely to be the same as those of the related mixture known as orcein, but in different proportions. In contrast with orcein, the principal constituent of litmus has an average molecular mass of $3300$.