Q1. [1] § 1.1 CHEMICAL EQUATIONS § 1.2.1 Combination Reaction
Which of the following are combination reactions ?
(i) 2KClO₃ ⎯⎯→ 2KCl + 3O₂
(ii) MgO + H₂O ⎯⎯→ Mg(OH)₂
(iii) 4Al + 3O₂ ⎯⎯→ 2Al₂O₃
(iv) Zn + FeSO₄ ⎯⎯→ ZnSO₄ + Fe
- (A) (i) and (iii)
- (B) (iii) and (iv)
- (C) (ii) and (iv)
- (D) (ii) and (iii)
Previously asked in CBSE board exam
2026 31/2/1 Q17
Generated by claude-sonnet-4-6 · 2026-06-14 10:31 · grounding rag
Model Answer
(D) (ii) and (iii)
In reaction (ii) MgO + H₂O → Mg(OH)₂ and (iii) 4Al + 3O₂ → 2Al₂O₃, two reactants combine to form a single product — these are combination reactions.
Explanation
A combination reaction is one where two or more substances combine to form a single product. Reaction (i) is decomposition (one reactant → multiple products) and reaction (iv) is a displacement reaction. Examiners expect students to correctly identify the defining feature: single product from multiple reactants.
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