Question

(a) What is Litmus? How is Litmus paper obtained?
(b) Write the method of preparation of Turmeric paper.

Answer 1

Hint: Litmus paper is a widely used tool to test whether a substance is acidic or basic. A litmus test is capable of providing a quick result but it cannot determine the level of acidity or basicity of a solution.

Complete answer:
(a) Litmus is the oldest form of indicator. It is made from different dyes extracted from Lichens. It is a water soluble mixture of different dyes. Litmus has purple colour in distilled water. Usually it is available as red and blue litmus paper.
Litmus paper is made by absorbing litmus solution onto filter paper. When a red litmus paper strip is dipped into basic solution it turns blue and when the blue litmus strip is dipped into acidic colour, it turns red in colour. Also, there is no colour change for neutral substances. Litmus is a very common acid-base indicator. Neutral litmus paper is purple in colour, it changes colour to blue or red depending upon the basicity or acidity of solution.
(b) Turmeric is also regarded as a natural indicator. Method of preparation of turmeric paper;
Firstly, take a tablespoon of turmeric powder (easily available at home), add a little water to it. A paste of turmeric powder will be obtained. Spread this turmeric paste on a piece of white paper or filter paper. Cut the paper into small strips after drying. Turmeric paper is ready to use.

Note:
Litmus is the most commonly used natural indicator. The main advantage is litmus paper is a handy acid-base indicator. There are some disadvantages of litmus paper as well; it doesn’t yield a numerical PH value.