Of two colourless solutions, the first gives a gas with magnesium and the second turns red litmus blue. What is the correct identification?
Answer and explanation
Correct answer: The first is acidic and the second is basic
The governing concept is the use of characteristic tests for acids and bases. Magnesium is above hydrogen in the reactivity series and reacts with an acid to release hydrogen gas, for example: Mg + 2HCl → MgCl₂ + H₂. Separately, a solution that changes red litmus to blue is basic. Therefore the first solution is acidic and the second is basic, so option A is correct; the other choices reverse or ignore these observations.
Frequently asked questions
What is the correct answer to this question?
The first is acidic and the second is basic
Why is this the correct answer?
The governing concept is the use of characteristic tests for acids and bases. Magnesium is above hydrogen in the reactivity series and reacts with an acid to release hydrogen gas, for example: Mg + 2HCl → MgCl₂ + H₂. Separately, a solution that changes red litmus to blue is basic. Therefore the first solution is acidic and the second is basic, so option A is correct; the other choices reverse or ignore these observations.
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.
