Chemistry GK Questions Quiz-25

Chemistry GK Questions Quiz-25

Chemistry Multiple Choice Questions (MCQs) Quiz for State and UPSC Civil Services Examinations. Objective Questions on Chemistry for competitive examinations.

    481. Of the following which one pollutes the air of a big city ?

    (1) Copper 
    (2) Chromium
    (3) Lead 
    4) Calcium
    Answer:
    481. (3) Lead pollution primarily came from cars in the past. Today, lead pollution primarily comes from lead smelters, metal processing plants and incinerators. Deposits of lead in soil can harm both humans and animals by absorbing it into a body.

    482. “Fire-fighting clothes” are made from

    (1) Mica 
    (2) Asbestos
    (3) Talc 
    (4) Steatite
    Answer:
    482. (2) Bunker Gear or "Turnout Gear" are terms used by many firefighters to refer to their system of outer protective clothing. Fire fighter used to be made of asbestos in the past. Because of its carcinogenic properties and other harmful effects, it has slowly been replaced by other substitutes. Fire-fighting and working clothes and accessories for firemen, rescuers and industrials made of materials FR cotton, Nomex, Modacryl, FR viscose and others.

    483. Water gas is the mixture of

    (1) carbon dioxide and hydrogen
    (2) carbon monoxide and nitrogen
    (3) carbon monoxide and hydrogen
    (4) carbon dioxide and nitrogen
    Answer:
    483. (3) Water gas, a mixture of carbon monoxide and hydrogen, is produced by treating carbon (in the form of coke or coal) with steam at high temperatures.

    484. Brass is made of

    (1) copper and tin
    (2) tin and lead
    (3) copper and zinc
    (4) copper, tin and zinc
    Answer:
    484. (3) Brass is an alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties. By comparison, bronze is principally an alloy of copper and tin.

    485. Which of the following causes the rusting of iron?

    a. Oxidation
    b. Reduction
    c. Chemical reaction with oxygen
    d. Chemical reaction with CO2
    (1) a and b 
    (2) b and c
    (3) c and d 
    (4) a and c
    Answer:
    485. (4) Rust is composed of iron oxides. In colloquial usage, the term is applied to red oxides, formed by the reaction of iron and oxygen in the presence of water or air moisture. When impure (cast) iron is in contact with water, oxygen, or other strong oxidants, or acids, it rusts. If salt is present, for example in seawater or salt spray, the iron tends to rust more quickly, as a result of electrochemical reactions.

    486. Which type of fire extinguisher is used for petroleum fire ?

    (1) Foam type
    (2) Soda acid type
    (3) Powder type
    (4) None of these
    Answer:
    486. (1) Foam type fire extinguishers are suitable for fires that involve flammable or combustible liquids, including petrol, grease, and oil. They are applied to fuel fires as either an aspirated (mixed & expanded with air in a branch pipe) or nonaspirated form to form a frothy blanket or seal over the fuel, preventing oxygen reaching it. Powder types are useful for combustible metals.

    487. The function of skimming tank in sewage treatment is to remove

    (1) oil and fatty substances
    (2) suspended solids
    (3) gritty substances
    (4) inorganic substances
    Answer:
    487. (1) Oil and grease traps are small size skimming basins provided to remove oil and grease and other small floating materials such as fats, vegetable debris, fruit skins, etc. It is so designed that lighter materials like grease and oil content of wastewater rise to the surface of wastewater and remains on top of liquid until removed.

    488. Which one of the following is not a ‘green house gas’ ?

    (1) Chlorofluorocarbons
    (2) Methane
    (3) Carbon dioxide
    (4) Nitrogen
    Answer:
    488. (4) The primary greenhouse gases in the Earth's atmosphere are water vapour, carbon dioxide,
    methane, nitrous oxide, and ozone. The anthropogenic compound of Chlorofluorocarbons is also a greenhouse gas, with a much higher potential to enhance the greenhouse effect than CO2.

    489. Black lung disease occurs in people working in

    (1) Electroplating industry
    (2) Organic solvents industry
    (3) Paint manufacturing industry
    (4) Coal mines
    Answer:
    489. (4) Coal worker's pneumoconiosis, colloquially referred to as black lung disease, is a lung disease that results from breathing in dust from coal, graphite, or manmade carbon over a long period of time. Inhaled coal dust progressively builds up in the lungs and is unable to be removed by the body; that leads to inflammation, fibrosis, and in worse cases, necrosis.

    490. Which one of the following is known as the ‘brown coal’ ?

    (1) Anthracite
    (2) Bituminous
    (3) Coke
    (4) Lignite
    Answer:
    490. (4) Lignite, often referred to as brown coal, is a soft brown fuel with characteristics that put it somewhere between coal and peat. It is considered the lowest rank of coal. It has a carbon content of around 25- 35%, a high inherent moisture content sometimes as high as 66%, and an ash content ranging from 6% to 19% compared with 6% to 12% for bituminous coal.

    491. The chief source of naphthalene is

    (1) Coal-tar 
    (2) Diesel
    (3) Charcoal 
    (4) Camphor
    Answer:
    491. (1) Coal tar is a brown or black liquid of extremely high viscosity. In the coal gas era, there were many companies in Britain whose business was to distill coal tar to separate the higher-value fractions, such as naphtha, creosote and pitch. Naphthalene is derived from a kind of naphtha (a broad term encompassing any volatile, flammable liquid hydrocarbon mixture, including coal tar).

    492. Why is water not suitable for putting out a petrol fire ?

    (1) The oxygen content of water is isolated by petrol and thus it helps in burning
    (2) Petrol is too inflammable to be extinguished by water
    (3) The heat required for combustion of petrol is very low
    (4) Water, being heavy, slips below petrol which thus remains in contact with air and burns
    Answer:
    492. (4) Water is not effective on petrol fire because it has higher density than petrol as a result of which it sinks to the bottom, while petrol stays afloat and keeps burning. Petro-chemical fires are nearly always extinguished with chemical foam which forms a blanket over the flames and cuts off the oxygen
    supply.

    493. Milk is

    (1) Emulsion 
    (2) Suspension
    (3) Foam 
    (4) Gel
    Answer:
    493. (1) An emulsion is a mixture of two liquids that cannot combine into a solution. In the case of milk, butterfat globules are suspended in a water-based fluid. The globules are encased in membranes that prevent them from combining into giant lumps of butterfat.

    494. The chemical substance present in bones and teeth is

    (1) Calcium phosphate
    (2) Calcium chloride
    (3) Calcium sulphate
    (4) Calcium borate
    Answer:
    494. (1) Seventy percent of bone consists of hydroxyapatite, a calcium phosphate mineral (known as bone mineral). Tooth enamel is composed of almost ninety percent hydroxylapatite.

    495. Maximum permissible concentration of copper in drinking water in mg/L is

    (1) 0.01 
    (2) 0.05
    (3) 1.0 
    (4) 2.0
    Answer:
    495. (3) The 1959 WHO International Standards for Drinking Water suggested that concentrations of
    copper greater than 1.5 mg/litre would markedly impair the potability of the water. However, in the
    first edition of the Guidelines for Drinking Water Quality, published in 1984, a guideline value of 1.0
    mg/litre was established for copper, based on its laundry and other staining properties.

    496. If lime water is kept in the air, it turns milky due to presence of :

    (1) Carbondioxide
    (2) Nitrogen
    (3) Oxygen
    (4) Sulphurdioxide
    Answer:
    496. (1) Lime water is calcium hydroxide (Ca(OH)2 ). When carbon dioxide is passed into it, it turns milky because of the formation of calcium carbonate: Ca(OH)2 + CO2® CaCO3 + H2O

    497. Heavy metal pollution of water is caused by:

    (1) Paints
    (2) Wood burning
    (3) Acid Plants
    (4) Domestic sewage
    Answer:
    497. (1) Heavy metals (cadmium, cobalt, chromium, copper, mercury, manganese, nickel, lead, zinc, molybdenum, tin) are among the main pollutants. Industrial paints are loaded with metals such as lead, calcium, cadmium and other such chemicals. When any amount of paint is led off into the water bodies it causes water pollution by causing the amount of heavy metals present in water to fluctuate. Each one of these has severe toxic effects on living beings, and tend to accumulate in aquatic food chains.

    498. The inert gas which is substituted for nitrogen in the air used by deep sea divers for Breathing is:

    (1) Neon 
    (2) Argon
    (3) Krypton 
    (4) Helium
    Answer:
    498. (4) Helium is used since it has very low (almost nonexistent) narcotic properties. The nitrogen in air is highly narcotic at depth and adding helium allows one to dive without the effects of narcosis (where one's mind is impaired).

    499. Asbestos is formed of :

    (1) Calcium and Magnesium
    (2) Copper, Zinc and Manganese
    (3) Lead and Iron
    (4) Calcium and Zinc
    Answer:
    499. (1) Pure and simple, asbestos is a group of naturally occurring minerals. It is composed of calcium and magnesium silicate. Asbestos occurs as veins in rocks and is mined from the ground, similar to coal.

    500. Why is water not suitable for putting out a petrol fire ?

    (1) The oxygen content of water is isolated by petrol and thus it helps in burning 
    (2) Petrol is too inflammable to be extinguished by water
    (3) The heat required for combustion of petrol is very low
    (4) Water, being heavy, slips below petrol which thus remains in contact with air and burns
    Answer:
    500. (4) Water is not effective on petrol fire because it has higher density than petrol as a result of which it sinks to the bottom, while petrol stays afloat and keeps burning. Petro-chemical fires are nearly always extinguished with chemical foam.


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