Which one of the following statements about diamond and graphite is not correct?
- A.Diamond has a tetrahedral structure, whereas graphite has a hexagonal planar structure.
- B.Both physical and chemical properties of diamond and graphite are different.
- C.Graphite is soft but diamond is hard.
- D.Graphite is a good conductor of electricity while diamond is not.
Correct answer
Explanation
The correct answer is B. Diamond and graphite are allotropes of the same element, carbon, so their chemical properties are the same; only their physical properties differ.
Allotropes are different forms of one element in the same physical state. In diamond each carbon atom is bonded to four others in a rigid three-dimensional tetrahedral network, which makes it the hardest natural substance and a non-conductor. In graphite each carbon is bonded to three others in flat hexagonal layers held together by weak forces, so the layers slide over one another, and the fourth electron of each atom is free to move, which lets graphite conduct electricity. Burnt in oxygen, both give only carbon dioxide, which shows they are chemically the same.
A is wrong as a choice: diamond is tetrahedral and graphite is made of hexagonal layers.
C is wrong as a choice: graphite is soft and slippery while diamond is very hard.
D is wrong as a choice: graphite conducts electricity and diamond does not.
Exam tip: allotropes share chemical properties and differ in physical ones; graphite is the only non-metal that conducts well.
Practice Questions
View allThe fact that the planets move around the Sun, not in circles but in ellipses, was first demonstrated by
- A.Galileo
- B.Martin Luther
- C.Johannes Kepler
- D.Copernicus
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In 1609 Kepler showed that the planets move around the Sun in elliptical orbits, with the Sun at one focus of the ellipse.
Read the full explanation →Which one of the following statements is correct?
- A.Urea is produced in liver.
- B.Urea is produced in blood.
- C.Urea is produced from digestion of starch.
- D.Urea is produced in lung and kidney.
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Liver cells turn the toxic ammonia released from the breakdown of amino acids into urea through the ornithine cycle, also called the urea cycle.
Read the full explanation →Which one of the following is the correct sequence of passage of light in a compound microscope?
- A.Condenser-Objective lens-Eyepiece-Body tube
- B.Objective lens-Condenser-Body tube-Eyepiece
- C.Condenser-Objective lens-Body tube-Eyepiece
- D.Eyepiece-Objective lens-Body tube-Mirror
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Light passes through the condenser to the specimen, is picked up by the objective lens, travels up the body tube and reaches the eye through the eyepiece.
Read the full explanation →Which one of the following statements regarding haemoglobin is correct?
- A.Haemoglobin present in RBC can carry only oxygen but not carbon dioxide.
- B.Haemoglobin of RBC can carry both oxygen and carbon dioxide.
- C.Haemoglobin of RBC can carry only carbon dioxide.
- D.Haemoglobin is only used for blood clotting and not for carrying gases.
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It binds oxygen at its iron-containing haem groups and carries some carbon dioxide on its protein chains. Each haemoglobin molecule has four polypeptide chains and four haem groups, and each haem iron can hold one oxygen molecule, forming oxyhaemoglobin in the lungs.
Read the full explanation →Which one of the following statements regarding histone proteins is correct?
- A.Histones are proteins that are present in mitochondrial membrane.
- B.Histones are proteins that are present in nucleus in association with DNA.
- C.Histones are proteins associated with lipids in the cytosol.
- D.Histones are proteins associated with carbohydrates in the cytosol.
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They are the proteins around which DNA winds to form chromatin in the nucleus of eukaryotic cells. Histones are small basic proteins, rich in the positively charged amino acids lysine and arginine, which attract the negatively charged phosphate groups of DNA.
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