Q1. [1] medium thorough-understanding
Which of the following correctly explains why hydrogen gas is NOT produced when copper reacts with dilute hydrochloric acid?
(A) Copper reacts with HCl to form an insoluble salt that blocks further reaction.
(B) Copper lies below hydrogen in the reactivity series and therefore cannot displace hydrogen from an acid.
(C) Copper reacts with HCl but the hydrogen produced immediately reacts back with copper.
(D) Copper requires concentrated acid, not dilute acid, to produce hydrogen.
- A Copper reacts with HCl to form an insoluble salt that blocks further reaction.
- B Copper lies below hydrogen in the reactivity series and therefore cannot displace hydrogen from an acid.
- C Copper reacts with HCl but the hydrogen produced immediately reacts back with copper.
- D Copper requires concentrated acid, not dilute acid, to produce hydrogen.
Generated by claude-sonnet-4-6 · 2026-06-26 01:05 · grounding rag
Model Answer
(B) Copper lies below hydrogen in the reactivity series and therefore cannot displace hydrogen from an acid.
Explanation
The reactivity series determines which metals can displace hydrogen from dilute acids. Only metals placed above hydrogen in the reactivity series (like Zn, Fe, Mg) can displace it. Copper is below hydrogen, so it cannot reduce H⁺ ions to H₂ gas. This is the standard CBSE reason; options A, C, and D are factually incorrect.