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.