Question

A solution of sodium chloride will:
A. turn red litmus blue
B. turn blue litmus red
C. turn red litmus orange
D. not change the colour of either red or blue litmus

Answer 1

Hint: Sodium chloride commonly known as table salt, is an ionic compound with the chemical formula NaCl. The response of salt solution to litmus paper varies on the pH of a solution which in turn depends upon what type of salt it is, whose solution is to be tested. An aqueous solution of a salt of strong acid and strong base is neutral, and will not respond to the litmus paper. e.g. NaCl.

Complete step by step answer:
-Litmus paper is a paper which is treated with an indicator which is a mixture of 10 to 15 natural dyes obtained from lichens.
-The main use of litmus is to test whether a solution is acidic or basic. Blue litmus paper turns red under acidic conditions and red litmus paper turns blue under basic or alkaline conditions, with the color change occurring over the pH range 4.5–8.3 at 25 °C. When the pH is neutral (pH = 7), then the dye is purple.
-NaCl is formed from a strong acid which is hydrochloric acid, and a strong base which is sodium hydroxide. Thus, when NaCl is dissolved in water it gets hydrolyzed to give an equal number of hydroxide and hydrogen ions, which makes the aqueous solution neutral. -Therefore, as NaCl is a neutral compound it will not have any effect on the blue as well as the red litmus paper.

Hence, option D is the correct answer.

Note:
Although the litmus test is quick and simple, it suffers from a few limitations.
1. It's not an accurate indicator of pH as it does not yield a numerical pH value. Instead, it indicates very roughly whether a sample is an acid or a base.
2. The paper can change colors for other reasons besides an acid-base reaction.