Q1. [1] § 1.1 CHEMICAL EQUATIONS § 1.1.1 Writing a Chemical Equation § 1.2.4 Double Displacement Reaction
Consider the following chemical equation I and II
I. Mg + 2HCl ⟶ MgCl₂ + H₂
II. NaOH + HCl ⟶ NaCl + H₂O
The correct statement about these equations is –
- (a) 'I' is a displacement reaction and 'II' is a decomposition reaction.
- (b) 'I' is a displacement reaction and 'II' is double displacement reaction.
- (c) Both 'I' and 'II' are displacement reactions.
- (d) Both 'I' and 'II' are double-displacement reactions.
Previously asked in CBSE board exam
2023 31/6/1 Q12
Generated by claude-sonnet-4-6 · 2026-06-15 06:46 · grounding rag
Model Answer
(b) 'I' is a displacement reaction and 'II' is a double displacement reaction.
In equation I, Mg displaces H from HCl (single displacement). In equation II, Na⁺ and H⁺ exchange partners — a double displacement (neutralisation) reaction.
Explanation
- Displacement reaction: One element displaces another from a compound. Here, Mg displaces H₂ from HCl.
- Double displacement reaction: Ions of two compounds exchange places. In NaOH + HCl, Na⁺ pairs with Cl⁻ and H⁺ pairs with OH⁻ to form water — classic neutralisation = double displacement.
- Common mistake: Students label II as "neutralisation only" and forget neutralisation is a type of double displacement reaction.
If a question refers to an image, map, graph or diagram that is not shown here, find the actual CBSE question paper on the CBSE website:
cbse.gov.in.