An aqueous solution of a salt turns red litmus blue. From which pair is this salt more likely to be formed?
Answer and explanation
Correct answer: A weak acid and a strong base
Red litmus turning blue indicates that the salt solution is basic. A salt formed from a weak acid and a strong base commonly gives a basic solution because the anion of the weak acid hydrolyses water and produces hydroxide ions; sodium carbonate is a familiar example. A strong-acid/weak-base salt is generally acidic, while a strong-acid/strong-base salt is approximately neutral. Hence A is correct.
Frequently asked questions
What is the correct answer to this question?
A weak acid and a strong base
Why is this the correct answer?
Red litmus turning blue indicates that the salt solution is basic. A salt formed from a weak acid and a strong base commonly gives a basic solution because the anion of the weak acid hydrolyses water and produces hydroxide ions; sodium carbonate is a familiar example. A strong-acid/weak-base salt is generally acidic, while a strong-acid/strong-base salt is approximately neutral. Hence 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.
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