Calcium hydroxide solution is passed through excess carbon dioxide gas. Name the type of reaction that occurs, write the balanced chemical equation, and state one observable change you would expect.
Generated by claude-sonnet-4-6 · 2026-06-26 00:54 · grounding rag
Model Answer
Type of reaction: Combination reaction
Balanced chemical equation:
$$\text{Ca(OH)}_2(aq) + \text{CO}_2(g) \rightarrow \text{CaCO}_3(s) + \text{H}_2\text{O}(l)$$
Observable change: A white precipitate of calcium carbonate (CaCO₃) is formed, turning the clear lime water solution milky/cloudy.
Source: Chapter 1, Section 1.2.1 Combination Reaction
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Explanation
- The examiner expects you to correctly name the reaction type (combination — two reactants form one main product), give the balanced equation with state symbols, and state one visible change.
- The white precipitate/milky appearance is the key observable here — examiners specifically look for this.
- Note: excess CO₂ does not convert CaCO₃ further in the NCERT Class 10 context; the equation given in the textbook (1.14) is the expected answer.
- Always include state symbols (aq), (g), (s), (l) — they can fetch you marks.