Which of the following substances turns red litmus paper blue in an aqueous solution?
Answer and explanation
Correct answer: Sodium hydroxide
Sodium hydroxide dissociates in water to produce hydroxide ions, OH⁻. The presence of these ions gives the solution basic properties, including the ability to turn red litmus paper blue. Hydrochloric acid is acidic and would show the opposite litmus behaviour. Sodium chloride solution and distilled water are approximately neutral, so they normally do not produce this colour change. Therefore, option A is correct.
Frequently asked questions
What is the correct answer to this question?
Sodium hydroxide
Why is this the correct answer?
Sodium hydroxide dissociates in water to produce hydroxide ions, OH⁻. The presence of these ions gives the solution basic properties, including the ability to turn red litmus paper blue. Hydrochloric acid is acidic and would show the opposite litmus behaviour. Sodium chloride solution and distilled water are approximately neutral, so they normally do not produce this colour change. Therefore, option A is correct.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Acids, Bases, and Salts.
