Cinnabar is an ore of

Q: What is the answer to CAPF 2022 Paper I Q36?

A. Correct — A, mercury. Cinnabar is mercury(II) sulphide, HgS, a brilliant red mineral and the chief ore from which mercury has been won since antiquity. The metal is obtained by roasting the ore in air — HgS + O₂ gives Hg + SO₂ — after which the mercury vapour is condensed. The same mineral, ground fine, is the pigment vermilion.

(a)mercury
(b)zinc
(c)copper
(d)lead

Answer

Why

Correct — A, mercury. Cinnabar is mercury(II) sulphide, HgS, a brilliant red mineral and the chief ore from which mercury has been won since antiquity. The metal is obtained by roasting the ore in air — HgS + O₂ gives Hg + SO₂ — after which the mercury vapour is condensed. The same mineral, ground fine, is the pigment vermilion.

Why the others are wrong

(b)zinc — Zinc comes from zinc blende (sphalerite, ZnS) and calamine (ZnCO₃). Zinc blende is also a sulphide, which is what makes this the most plausible wrong answer.
(c)copper — Copper's principal ores are copper pyrites (chalcopyrite, CuFeS₂) and malachite. Cinnabar contains no copper.
(d)lead — Lead comes from galena, PbS — another sulphide, but a grey metallic-looking one, quite unlike cinnabar's red.

Concept

Ore names are a fixed vocabulary in this syllabus, and cinnabar belongs to mercury. Most of the heavy metals of the p-block and late d-block occur as sulphides, so the discriminator is not the sulphide ending but the specific mineral name.

Every wrong option is a metal whose common ore is also a sulphide, which is exactly why the item works. Fix the pairs by name rather than by chemistry: cinnabar to mercury, galena to lead, zinc blende to zinc, copper pyrites to copper. Mercury is worth remembering for a second reason — it is the only metal that is liquid at ordinary room temperature.

Key facts

Cinnabar is HgS, mercury(II) sulphide, and is the source of the pigment vermilion.
Roasting the ore in air gives the free metal directly: HgS + O₂ → Hg + SO₂.
Other sulphide ores worth pairing: galena PbS (lead), zinc blende ZnS (zinc), copper pyrites CuFeS₂ (copper), iron pyrites FeS₂.
Mercury is liquid at room temperature and is used in thermometers, barometers and fluorescent lamps; its compounds are cumulative poisons, as the Minamata episode in Japan showed.

A cluster of deep red cinnabar crystals grown on white quartz and dolomite — Cinnabar, mercury(II) sulphide, the chief ore of mercury and the mineral from which the red pigment vermilion is ground.Image: Robert M. Lavinsky · Wikimedia Commons (CC BY-SA 3.0)

Study next

Common ores and their metals — bauxite, haematite, galena, zinc blende, cryptic mineral namesRoasting and calcination as the two preliminary steps of metallurgyProperties and uses of mercury, and mercury poisoningThe reactivity series and how it decides the extraction methodSulphide ores and froth flotation

Common traps

Choosing zinc or lead because their ores are sulphides too.
Confusing cinnabar with cassiterite, the tin ore, on the strength of the similar-sounding name.
Assuming a red mineral must be an iron ore.

Asked as a direct ore-to-metal pairing, or inside a matching list of four ores against four metals.

Related PYQs

NDA_GAT_2021_II_Q1252021Open & attempt →

Cinnabar is an ore of which one of the following?

(a) Copper
(b) Zinc
(c) Mercury
(d) Manganese

Answer(c) Mercury

The identical pairing asked a year earlier, with manganese swapped in for lead among the distractors. Ore names recur across these papers almost unchanged, so the list is worth learning as a list.

Practice

practice — not a real PYQ
Galena is an ore of
- (a)zinc
- (b)lead
- (c)tin
- (d)mercury
Answer(b) lead — galena is lead sulphide, PbS, the principal lead ore.
practice — not a real PYQ
Which one of the following metals is liquid at ordinary room temperature?
- (a)Sodium
- (b)Mercury
- (c)Lead
- (d)Zinc
Answer(b) Mercury — its melting point is about −39 °C, which is why it is used in thermometers and barometers.