The elemental composition of diamond is
- A.Carbon and Hydrogen
- B.Carbon and Oxygen
- C.Pure Carbon
- D.Pure Silicon
Correct answer
Explanation
The correct answer is C, Pure Carbon. Diamond is an allotrope of carbon, made of carbon atoms alone and nothing else.
In diamond each carbon atom is joined to four other carbon atoms by strong covalent bonds, forming a rigid three-dimensional network. This makes diamond the hardest natural substance and a bad conductor of electricity, since it has no free electrons. Graphite, another allotrope, is also pure carbon, but its atoms lie in layers, so it is soft and conducts electricity. Burning diamond in oxygen gives only carbon dioxide, which proves it is pure carbon.
A is wrong because carbon with hydrogen makes hydrocarbons such as methane, not diamond. B is wrong because carbon with oxygen makes gases such as carbon dioxide and carbon monoxide. D is wrong because silicon is a different element; it forms sand and quartz as silica.
Exam tip: diamond, graphite and fullerene are all pure carbon; diamond is hard and an insulator, graphite is soft and a conductor.
Practice Questions
View allWhich one of the following is monatomic?
- A.Hydrogen
- B.Sulphur
- C.Phosphorus
- D.Helium
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A monatomic element exists as single, separate atoms. Helium is a noble gas of group 18: its only shell, the first, is full with two electrons, so a helium atom has no tendency to share or transfer electrons and does not bond even with another helium atom.
Read the full explanation →The normal systolic pressure in human beings is :
- A.80 mm of Hg
- B.100 mm of Hg
- C.120 mm of Hg
- D.140 mm of Hg
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Blood pressure is written as two numbers, and normal adult blood pressure is about 120/80 mm of mercury.
Read the full explanation →'Study of human societies and cultures from the oldest times to the present' is the work of
- A.Archaeologists
- B.Anthropologists
- C.Palaeontologists
- D.Geologists
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Anthropology, from the Greek 'anthropos' (human) and 'logos' (study), is the science of human beings: how societies and cultures began, how they changed and how people live today.
Read the full explanation →Which of the following catalytic systems is used for the reduction of unsaturated hydrocarbon to saturated hydrocarbon?
- A.Copper and H2
- B.Iron and H2
- C.Zinc and H2
- D.Nickel and H2
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Adding hydrogen across the double or triple bond of an alkene or alkyne turns it into a saturated alkane; this reaction is called hydrogenation and it needs a catalyst.
Read the full explanation →Which one among the following is not a plant hormone ?
- A.Gibberellins
- B.Abscisic acid
- C.Auxins
- D.Thyroxine
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Thyroxine is an animal hormone, made by the thyroid gland in the neck, and it controls the rate of metabolism in the human body.
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