This set of Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Occurrence of Metals”.
1. Which of the following is the chief ore of aluminium?
Explanation: Bauxite is the chief ore of aluminium. The composition of bauxite is Al2O3.2H2O, it’s a mixture of hydrated iron oxide and hydrated aluminium oxide. Kaolinite is another ore of aluminium but its less availability is less compare to bauxite and the extraction of aluminium from kaolinite is a hard process and costs more.
2. Which of the following is the finest iron ore?
d) Iron Pyrites
Explanation: Magnetite is the finest iron ore with a very high content of iron up to 72 percent. It has a very good magnetic property and is valuable in electrical industry. Hematite is another very important iron ore but the iron content of hematite is slightly lower than magnetite.
3. What is the composition of Kaolinite?
Explanation: Kaolinite is a soft clay type material with the chemical composition [Al2(OH)4Si2O4]. It’s basically made up of hydrous aluminium silicates, they comprise the principle ingredients of kaolin (china clay). It is usually white in appearance and sometimes red due to iron oxide.
4. What is the composition of brass?
a) 49 percent copper and 51 percent zinc
b) 50 percent copper and 50 percent zinc
c) 37 percent copper and 63 percent zinc
d) 63 percent copper and 37 percent zinc
Explanation: Brass is an alloy of copper and zinc, typically 63 percent copper and 37 percent zinc. Sometimes poor quality brass may contain a little lead. Brass is naturally corrosion resistant and has very low friction. It is used for construction of water pipes and fittings.
5. Which of the following is not a suitable ore for extracting iron?
d) Iron Pyrites
Explanation: The composition of iron pyrite is FeS2. Iron pyrite is exothermic and can cause hazard in mines, it is more economical to extract iron from other ores such as magnetite and hematite. Pyrites are generally unstable and might turn into sulfurous minerals.
6. Malachite is an ore of copper with 58 percent copper concentration.
Explanation: Malachite is a copper ore with composition CuCO3.Cu(OH)2. It contains around 58 percent copper and is bright green in color, it is a hydrous carbonate mineral and it’s a common but minor ore of copper.
7. What is the concentration of zinc in calamine?
a) 98 percent
b) 94 percent
c) 86 percent
d) 74 percent
Explanation: The chemical composition of calamine is ZnCO3 with 98 percent concentration of zinc. It is available in abundance and can be artificially prepared in laboratories. It is used in medication to relieve pain and itching.
8. The composition of bronze is generally 82 percent copper and 18 percent tin.
Explanation: Bronze is an alloy consisting mainly of copper and with other metals generally tin. The composition of bronze is 88 percent copper and 12 percent tin it may also contain small amount of aluminium, manganese, zinc and silicon.
9. Silver is extracted from which of the following ore?
Explanation: Argentite also knows as silver glance is the only given silver ore in the above options with chemical composition Ag2S. Silver is extracted from silver glance by a simple process known as smelting or chemical leaching.
10. Which metal is extracted from Cinnabar?
Explanation: Cinnabar also known as cinnabarite is a natural and the only important ore of mercury with chemical composition HgS. Cinnabar is a toxic ore because of the presence of high amount of mercury and cannot be handled directly.
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