Some metal oxides react with acid as well as a base to produce salt and water. They are known as amphoteric oxides. Examples of amphoteric oxides are
- A.CuO and ZnO
- B.Al₂O₃ and ZnO
- C.Al₂O₃ and CuO
- D.More than one of the above
Correct answer
Explanation
The correct answer is B, Al₂O₃ and ZnO. Aluminium oxide and zinc oxide behave like a base with acids and like an acid with bases, so both are amphoteric. With hydrochloric acid, aluminium oxide gives aluminium chloride and water. With sodium hydroxide, zinc oxide gives sodium zincate and water. The word amphoteric comes from the Greek for 'both', which is the easiest way to remember it. Most metal oxides are basic, while oxides of non-metals such as carbon dioxide and sulphur dioxide are acidic. Other common amphoteric oxides are those of lead and tin. Option A is wrong because copper(II) oxide is a basic oxide; it reacts with acids but not with bases. Option C is wrong for the same reason, as it also pairs aluminium oxide with basic copper oxide. Option D is wrong because only one pair, B, has both oxides amphoteric. Exam tip: remember the amphoteric four as Al, Zn, Pb and Sn, that is aluminium, zinc, lead and tin.
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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