Why is hydrogen gas generally not evolved when dilute hydrochloric acid is added to copper?
Answer and explanation
Correct answer: Copper is less reactive than hydrogen
The governing concept is the metal reactivity series. A metal releases hydrogen from a dilute non-oxidising acid only when it is above hydrogen in the series and can displace H⁺ ions. Copper lies below hydrogen, so it does not normally react with dilute hydrochloric acid to produce H₂. It does not dissolve simply in water, hydrochloric acid is an acid, and the statement that copper always forms gas is false. Thus option A is correct.
Frequently asked questions
What is the correct answer to this question?
Copper is less reactive than hydrogen
Why is this the correct answer?
The governing concept is the metal reactivity series. A metal releases hydrogen from a dilute non-oxidising acid only when it is above hydrogen in the series and can displace H⁺ ions. Copper lies below hydrogen, so it does not normally react with dilute hydrochloric acid to produce H₂. It does not dissolve simply in water, hydrochloric acid is an acid, and the statement that copper always forms gas is false. Thus 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.
