Which of the following substances turns red litmus paper blue when dissolved in water?
Answer and explanation
Correct answer: Sodium hydroxide
Sodium hydroxide is a soluble base. When it dissolves in water, it produces hydroxide ions, OH⁻, making the solution alkaline; an alkaline solution turns red litmus paper blue. Therefore, option A is correct. Hydrochloric acid turns blue litmus red, whereas sodium chloride solution and distilled water are generally neutral and do not produce this change.
Frequently asked questions
What is the correct answer to this question?
Sodium hydroxide
Why is this the correct answer?
Sodium hydroxide is a soluble base. When it dissolves in water, it produces hydroxide ions, OH⁻, making the solution alkaline; an alkaline solution turns red litmus paper blue. Therefore, option A is correct. Hydrochloric acid turns blue litmus red, whereas sodium chloride solution and distilled water are generally neutral and do not produce this change.
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.
