Which one of the following metals can be extracted using carbon as reducing agent?
- A.Zinc
- B.Silver
- C.Gold
- D.Aluminum
Correct answer
Explanation
The correct answer is A, Zinc. Zinc lies in the middle of the reactivity series, so its oxide can be reduced to the metal by heating it with carbon (coke): ZnO + C → Zn + CO.
How a metal is extracted depends on its place in the reactivity series. Highly reactive metals such as sodium, magnesium and aluminium hold oxygen too strongly for carbon, so they are extracted by electrolysis. Metals of middle reactivity, such as zinc, iron and lead, are first converted to oxides by roasting or calcination and then reduced with carbon. Metals low in the series are found free or are obtained by simple heating.
B is wrong because silver is a low-reactivity metal found native or extracted from its ores by other methods, such as leaching with cyanide, without carbon reduction. C is wrong because gold is so unreactive that it occurs free in nature and is separated, not reduced. D is wrong because aluminium is more reactive than carbon and is extracted by electrolysis of alumina dissolved in molten cryolite.
Exam tip: top of the series by electrolysis, middle (Zn, Fe, Pb) by carbon reduction, bottom found free.
Practice Questions
View allWhich one of the following features is an indication for modification of stem of a plant?
- A.Presence of 'eye' on potato
- B.'Scale' found in onion
- C.'Tendril' found in pea
- D.'Hair' present in carrot
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The eyes of a potato are nodes with buds, and only a stem bears nodes and buds, so they prove that the potato is a modified stem.
Read the full explanation →Which one of the following metals is used in the filaments of photo-electric cells that convert light energy into electric energy ?
- A.Tungsten
- B.Copper
- C.Rubidium
- D.Aluminium
Show answer
Rubidium, an alkali metal like caesium, gives off electrons easily when light falls on it, so it is used in photoelectric cells.
Read the full explanation →Tooth enamel is made up of which one of the following calcium compounds ?
- A.Calcium carbonate
- B.Calcium sulphate
- C.Calcium hydroxide
- D.Calcium phosphate
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Tooth enamel is made mainly of calcium phosphate in the form of a hard crystal called hydroxyapatite. Enamel is the hardest substance in the human body, harder even than bone.
Read the full explanation →Which one of the following viruses used to be responsible for highly infectious disease Smallpox ?
- A.Adenovirus
- B.Variola virus
- C.Aichi virus
- D.Coxsackie virus
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Smallpox was caused by the variola virus, a large DNA virus of the pox family that spread from person to person through the air.
Read the full explanation →After fertilization, the fruit and the seed are produced by
- A.ovule and ovary, respectively
- B.ovary and ovule, respectively
- C.ovary, no ovule required
- D.ovule, no ovary required
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After fertilisation the ovary of the flower grows into the fruit, and each ovule inside it develops into a seed.
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