Question

Comment on the following statement.
Nitric acid turns red litmus blue.
(A) True
(B) False

Answer 1

Hint- In order to solve the given problem and comment on the given statement, first we will see what is the litmus paper and what are its characteristics then we will understand under what circumstances a red litmus turns blue and blue litmus turns red. And also we will understand the indication of this change in colour of litmus paper.

Complete answer:
> Litmus is a water-soluble mixture derived from lichens with various dyes. Production of one of the oldest forms of pH indicator, used to test materials for acidity, is often adsorbed on filter papers.
> The primary raw materials used to make litmus paper are cellulose, lichens, and adjunct compounds made from wood. Litmus paper, as its name implies, is made predominantly of paper. The paper used to make litmus paper must be free of contaminants which could change the pH of the measuring system. Like most paper, litmus paper is made of cellulose made from wood.
> Litmus is used primarily to determine whether a solution is acidic or basic. For acidic solutions Litmus indicator solution turns red and alkaline solutions turn blue. This transforms neutral solutions into red. Litmus paper is generally more reliable, and comes in the form of red litmus paper and blue litmus. Litmus paper is used to decide whether a solution is acidic or normal. Litmus paper does not provide precise details about acid or base strength.
> As we know that nitric acid is an acid so due to its acidic nature eventually there will be no effect on treating red litmus paper with the nitric acid. Rather the nitric acid will turn blue litmus red.
Hence, the given statement is false. So, the correct answer is option B.

Note- The litmus paper is an indicator which just indicates the nature of the solution is acidic or basic but it does not tell about the strength of the acid or the base and also we don’t get any information about the pH of the solution. For those cases where we need pH value or the strength of the solution, we prefer pH paper and other test strips in the place of litmus paper.