Q1. [1] § 1.1 CHEMICAL EQUATIONS § 1.1.2 Balanced Chemical Equations § 1.2 TYPES OF CHEMICAL REACTIONS
Which one of the following reactions is different from the remaining three ?
- A NaCl + AgNO₃ → AgCl + NaNO₃
- B CaO + H₂O → Ca(OH)₂
- C KNO₃ + H₂SO₄ → KHSO₄ + HNO₃
- D ZnCl₂ + H₂S → ZnS + 2HCl
Previously asked in CBSE board exam
2024 31/3/1 Q7
Generated by claude-sonnet-4-6 · 2026-06-14 10:28 · grounding rag
Model Answer
Answer: (B)
CaO + H₂O → Ca(OH)₂ is a combination reaction, while reactions A, C, and D are all double displacement reactions (two ions/groups are exchanged between reactants).
Source: Chapter 1, Chemical Reactions and Equations
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Explanation
- Double displacement: two different ions/groups exchange between two compounds (A, C, D all fit this pattern).
- Combination reaction: two substances combine to form a single new substance — that's what B shows (CaO + H₂O → Ca(OH)₂).
- Examiners expect you to identify the odd one out by reaction type. Name the type for option B and briefly state why A, C, D belong to the same category.
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