Name the ore of mercury and state the form in which it is found in nature. Write the chemical equations along with the condition required for the reactions involved in the extraction of mercury from its ore.
Generated by claude-sonnet-4-6 · 2026-06-15 06:47 · grounding rag
Model Answer
Ore of Mercury: Cinnabar (HgS). It is found in the combined state (as a sulphide compound) in nature.
Extraction of Mercury:
Step 1: Cinnabar is heated strongly in air, converting it to mercuric oxide:
$$2\text{HgS(s)} + 3\text{O}_2\text{(g)} \xrightarrow{\text{Heat}} 2\text{HgO(s)} + 2\text{SO}_2\text{(g)}$$
Step 2: Mercuric oxide is further heated, and being a low-activity metal, it decomposes to give mercury:
$$2\text{HgO(s)} \xrightarrow{\text{Heat}} 2\text{Hg(l)} + \text{O}_2\text{(g)}$$
No reducing agent is needed; heat alone is sufficient because mercury is low in the activity series.
Source: Chapter 3, Section 3.4.3
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Explanation
- The question awards 1 mark for naming the ore and its form; 2 marks for the two balanced equations with conditions.
- Always write the condition (Heat) above the arrow and include state symbols — examiners check both.
- The key idea to state: since Hg is low in the activity series, simple heating suffices — no carbon reduction needed. Mentioning this shows conceptual understanding and can fetch full marks.