Home › Tamil Nadu HSC (Class 12) › Chemistry › Metallurgy › Cinnabar (HgS) is unusual because mercury can be…
Cinnabar (HgS) is unusual because mercury can be obtained from it simply by
Acarbon reduction
Broasting alone (auto-reduction)
Celectrolysis of the fused ore
Dhydrogen reduction
Answer & Solution
Correct answer: B. roasting alone (auto-reduction)
1. Roasting some ores directly gives the free metal without a separate reducing agent.
2. For cinnabar: $HgS + O_2 \rightarrow Hg + SO_2$; the sulphide itself is oxidised while the metal is set free.
3. This self-reduction on roasting is called **auto-reduction**.
_Source: Samacheer Kalvi Class 12 Chemistry Vol.1, Unit 1 'Metallurgy', §1.3.2 (Auto-reduction)_
Related questions
Germanium and silicon used as semiconductors are purified by zone refining becauseNickel is refined by heating the impure metal in a stream of CO to form a volatile carbonyFrom an Ellingham diagram at 1500 K, $\Delta G^\circ$ for $2Fe+O_2\rightarrow 2FeO$ is $-3From an Ellingham diagram, aluminium can reduce which of the following oxides?In an Ellingham diagram the line for the formation of carbon monoxide ($2C + O_2
ightarroAn Ellingham diagram is a plot ofIn the cyanide process, gold is recovered from the leached solution $[Au(CN)_2]^-$ by addiIn the electrolytic refining of copper, the anode and cathode are respectively