Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination.
41. The chemical substance present in bones and teeth is:
[A] Calcium phosphate
[B] Calcium chloride
[C] Calcium sulphate
[D] Calcium borate
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Correct Answer: A [Calcium phosphate]
Notes:
Seventy percent of bone consists of hydroxyapatite, a calcium phosphate mineral (known as bone mineral). Tooth enamel is composed of almost ninety percent hydroxylapatite. The other compound is tricalcium phosphate. (Ca3(PO4)2).
42. Which of the following is not a chemical reaction’?
[A] Burning of paper
[B] Digestion ot of food
[C] Conversion of water into steam
[D] Burning of coal
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Correct Answer: C [Conversion of water into steam]
Notes:
The conversion of water into steam is an example of a physical change, where the state of the matter changes without changing its composition. A physical change involves a change in physical properties. Examples of physical properties include melting, transition to a gas, change of strength, change of durability, changes to crystal form, textural change, shape, size, color, volume and density.
43. Which of the following is the common name of Phosgene?
[A] Carbonyl chloride
[B] Phosphine
[C] Carbon tetrachloride
[D] Phosphorus trichloride
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Correct Answer: A [Carbonyl chloride]
Notes:
Phosgene is the chemical compound with the formula COCl2. It is also known as Carbonyl dichloride. It is formed when chlorinated hydrocarbon compounds are exposed to high temperatures. Phosgene is a major industrial chemical used to make chemicals and Pesticides, but at room temperature it is a poisonous gas.
44. Maximum permissible concentration of total hardness in drinking water is:
[A] 50
[B] 100
[C] 200
[D] 500
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Correct Answer: C [200]
Notes:
Maximum permissible concentration of total hardness in drinking water in 200. It is a good source of minerals necessary for human health.
45. Surface water is a better source of drinking water because it is poor in:
[A] Dust
[B] Bacteria
[C] Arsenic
[D] Algae
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Correct Answer: C [Arsenic]
Notes:
Surface water is a better source of drinking water because it is poor in arsenic and other heavy metals. They being heavy sediment to water surface.
46. Combustion of a candle is a/an:
[A] photochemical reaction
[B] physical change
[C] endothermic reaction
[D] exothermic reaction
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Correct Answer: D [exothermic reaction]
Notes:
In theory, a candle is made of a solid hydrocarbon called paraffin. When the solid burns, the hydrocarbon reacts with oxygen to form carbon dioxide and water. The reaction is exothermic, meaning it releases heat to the atmosphere along with the other products.
47. Which of the following is a characteristic of an exothermic reaction?
[A] Release of heat
[B] Absorption of heat
[C] Doesn’t involve any change in temperature
[D] None of the above
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Correct Answer: A [Release of heat]
Notes:
An exothermic reaction is a chemical or physical reaction that releases heat. It gives net energy to its surroundings. Expressed in a chemical equation: reactants ? products + energy. It is the opposite of an endothermic reaction.
48. Which one of the following vegetable oils is used in the manufacture of paints?
[A] Palm oil
[B] Sunflower oil
[C] Linseed oil
[D] Cottonseed oil
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Correct Answer: C [Linseed oil]
Notes:
Linseed oil and castor oils are used mainly as drying agents in paints and varnishes. Linseed oil is generally used in the manufacture of oil paints, drying oil finish or varnish in wood finishing, as a pigment binder in oil paints, as a plasticizer and in the manufacture of linoleum.
49. Which of the following is used to make light weight, but strong plastic?
[A] Nylon
[B] Polythene
[C] Polyvinyl Chloride
[D] Methyl Methacrylate
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Correct Answer: C [Polyvinyl Chloride]
Notes:
Polyvinyl chloride (PVC) is a common, strong but lightweight plastic that is used in making tough plastic. It is used for flexible applications such as insulating cables. It is the third-most widely produced synthetic plastic polymer, after polyethylene and polypropylene.
50. Which of the following is not a natural source of hydrocarbon?
[A] Natural Gas
[B] Coal
[C] Petroleum
[D] Mica
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Correct Answer: D [Mica]
Notes:
There are three main natural sources of hydrocarbons: natural gas, petroleum and coal. Mica is a natural occurring mineral that is based on a collection of silicate minerals and composed of varying amounts of potassium, iron, aluminum, magnesium and water. It is widely used in the electrical industry.
