Chemistry GK Questions Quiz-15

Chemistry GK Questions Quiz-15

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

    281. For generation of biogas, the materials commonly used are

    (1) Animal wastes
    (2) Crop residues
    (3) Aquatic plants
    (4) Forest residues
    Answer:
    281. (1) Biogas typically refers to a gas produced by breakdown of organic matter in the absence of oxygen. Organic waste such as dead plant and animal material, animal feces, and kitchen waste can be converted into a gaseous fuel called biogas. Biogas originates from biogenic material and is a type of bio fuel. Biogas is produced by the anaerobic digestion or fermentation of biodegradable materials such as biomass, manure, sewage, municipal waste, green waste, plant material, and crops. Biogas comprises primarily methane (CH4) and carbon dioxide (CO2) and may have small amounts of hydrogen sulphide (H2S), moisture and siloxanes.

    282. Raw materials used for the manufacture of glass are

    (1) sand, soda, limestone
    (2) sand, charcoal, soda
    (3) limestone, charcoal, sulphur
    (4) sand, sulphur, soda
    Answer:
    282. (1) Quartz sand (silica) is the main raw material in commercial glass production. While fused quartz (primarily composed of SiO2) is used for some special applications, it is not very common due to its high glass transition temperature of over 1200 degree C (2192 degree F). Normally, other substances are added to simplify processing. One is sodium carbonate (Na2CO3, “soda”), which lowers the glass transition temperature. However, the soda makes the glass water soluble, which is usually undesirable, so lime (calcium oxide [CaO], generally obtained from limestone), some magnesium oxide (MgO) and aluminium oxide (Al2O3) are added to provide for a better chemical durability. The resulting glass contains about 70 to 74% silica by weight and is called a soda-lime glass. Soda-lime glasses account for about 90% of manufactured glass.

    283. Which of the following is used in welding broken pieces of iron rails and machine parts?

    (1) Aluminium sulphate
    (2) Solder
    (3) Aluminium powder
    (4) None of the above
    Answer:
    283. (3) Aluminum powder is a highly flammable powder created by grinding aluminum into fine grains of material. In times past, this flammable metal powder was used in photography to create bright flashes during a photographic session. Today, aluminum powder is one of the tools utilized in various applications of pyrotechnics, including the creation of fireworks displays. Used primarily as an inlay compound, the aluminum powder can easily be used to set cut pieces of wood into position and also fill in any tiny gaps that may be present at the joints. Since only a minute amount of powder is necessary for functions of this type, the chances of ignition are somewhat limited.

    284. The BOD values of water indicate the

    (1) amount of organic debris
    (2) amount of oxygen used for biochemical oxidation
    (3) amount of oxygen used for biochemical reduction
    (4) amount of ozone used for biochemical oxidation
    Answer:
    284. (2) Biochemical oxygen demand or B.O.D. is the amount of dissolved oxygen needed by aerobic
    biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period. The term also refers to a chemical procedure for
    determining this amount. This is not a precise quantitative test, although it is widely used as an indication of the organic quality of water. The BOD value is most commonly expressed in milligrams of
    oxygen consumed per litre of sample during 5 days of incubation at 20 degree C and is often used as a
    robust surrogate of the degree of organic pollution of water.

    285. Which of the following produces highest amount of energy upon oxidation?

    (1) Protein 
    (2) Fat
    (3) Glucose 
    (4) An alkane
    Answer:
    285. (2) Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure and composition. Although the words “oils”, “fats”, and “lipids” are all used to refer to fats, “oils” is usually used to refer to fats that are liquids at normal room temperature, while “fats” is usually used to refer to fats that are solids at normal room temperature. Fats also serve as energy stores for the body, containing about 37.8 kilojoules (9 calories) per gram of fat. They are broken down in the body to release glycerol and free fatty acids. The glycerol can be converted to glucose by the liver and thus used as a source of energy.

    286. The metals commonly used for electroplating are

    (1) Gold, Sodium and Chromium
    (2) Chromium, Copper and Nickel
    (3) Nickel, Lead and Chromium
    (4) Gold, Sodium and Potassium
    Answer:
    286. (2) The process of electroplating takes place as metals in ionic form move from a positive to negative electrode. An electric current passing through the solution causes objects at the cathode or work piece to be coated by the metal in the solution. Electroplating is done for many reasons, usually to beautify, insulate or to protect and to increase the corrosion resistance, conductivity solder ability of metal objects. Plating protects by one of two ways, either sacrificially or mechanically. Zinc and cadmium protect the base metals they cover sacrificially. They are more reactive to corrosion than iron or copper alloys so they corrode first, before the base metals. Copper, nickel, chromium and most other metals protect the base metals mechanically. They protect the base metals by forming a protective coating, therefore the protection is good only as long as that coating is intact. If there is defect or break in the protective coating the base metal will corrode before the plating.

    287. Which of the following in automobile exhaust can cause cancer?

    (1) Oxides of nitrogen
    (2) Carbon monoxide
    (3) Lead
    (4) Polyclinic hydrocarbons
    Answer:
    287. (4) Polycyclic aromatic hydrocarbons (PAHs) are formed during incomplete combustion. Domestic wood burning and road traffic are the major sources of PAHs. Exposure to PAH-containing substances increases the risk of cancer in humans. The carcinogenicity of PAHs is associated with the
    complexity of the molecule, i.e., increasing number of benzenoid rings, and with metabolic activation to
    reactive diol epoxide intermediates and their subsequent covalent binding to critical targets in DNA.
    Quantitative cancer risk estimates of PAHs as air pollutants are very uncertain because of the lack of
    useful, good-quality data.

    288. Bleaching powder is used in drinking water as a/an

    (1) disinfectant 
    (2) antibiotic
    (3) antiseptic 
    (4) coagulant
    Answer:
    288. (1) Bleach refers to a number of chemicals which remove colour, whiten or disinfect, often via oxidation. Bleaches are used as household chemicals to whiten clothes and remove stains and as disinfectants, primarily in the bathroom and kitchen. Many bleaches have strong bactericidal properties, and are used for disinfecting and sterilizing and thus are used in swimming pool sanitation to control bacteria, viruses and algae and in any institution where sterile conditions are needed. They are also used in many industrial processes, notably in the bleaching of wood pulp. Sodium hypochlorite solution, 3-6%, (common household bleach) must be diluted to be used safely when disinfecting surfaces and when used to treat drinking water.

    289. The iron ore which contains 72% of iron is :

    (1) Magnetite 
    (2) Limonite
    (3) Haematite 
    (4) Siderite
    Answer:
    289. (1) Iron (Fe) is a metallic element and composes about 5% of the Earth’s crust. When pure it is a dark, silvery-gray metal. It is a very reactive element and oxidizes (rusts) very easily. The reds, oranges and yellows seen in some soils and on rocks are probably iron oxides. The inner core of the Earth is believed to be a solid iron-nickel alloy. Iron-nickel meteorites are believed to represent the earliest material formed at the beginning of the universe. Studies show that there is considerable iron in the stars and terrestrial planets: Mars, the “Red Planet,” is red due to the iron oxides in its crust. The principle ores of iron are Hematite, (70% iron) and Magnetite, (72 % iron). Taconite is a low-grade iron ore, containing up to 30% Magnetite and Hematite.

    290. Cement is usually a mixture of :

    (1) Calcium silicate and calcium aluminate
    (2) Calcium silicate and calcium ferrate
    (3) Calcium aluminate and calcium ferrate
    (4) Lime stone and silicon dioxide
    Answer:
    290. (1) Portland cement is the most common type of cement in general use around the world because it is a basic ingredient of concrete, mortar, stucco and most nonspecialty grout. It usually originates from limestone. It is a fine powder produced by grinding Portland cement clinker (more than 90%), a limited amount of calcium sulfate (which controls the set time) and up to 5% minor constituents. Portland cement clinker is a hydraulic material which shall consist of at least two-thirds by mass of calcium silicates, the remainder consisting of aluminium- and iron-containing clinker phases and other compounds.

    291. The atmospheric gas that is mainly responsible for Green House effect :

    (1) Ozone 
    (2) Nitrogen
    (3) Oxygen 
    (4) Carbondioxide
    Answer:
    291. (4) A greenhouse gas (sometimes abbreviated GHG) is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth’s atmosphere are water vapour, carbon dioxide, methane, nitrous oxide, and ozone. In the Solar System, the atmospheres of Venus, Mars, and Titan also contain gases that cause greenhouse effects. Greenhouse gases greatly affect the temperature of the Earth; without them, Earth’s surface would average about 33 degree C (91 degree F) colder than the present average of 14 degree C (57 degree F).

    292. Electric bulbs are filled with :

    (1) Nitrogen
    (2) Carbon dioxide
    (3) Argon
    (4) Oxygen
    Answer:
    292. (3) Argon is produced industrially by the fractional distillation of liquid air. Argon is mostly used as an inert shielding gas in welding and other hightemperature industrial processes where ordinarily
    non-reactive substances become reactive; for example, an argon atmosphere is used in graphite electric
    furnaces to prevent the graphite from burning. Argon gas also has uses in incandescent and fluorescent
    lighting, and other types of gas discharge tubes. Argon makes a distinctive blue-green gas laser. Incandescent lights are filled with argon, to preserve the filaments at high temperature from oxidation. It is used for the specific way it ionizes and emits light, such as in plasma globes and calorimetry in experimental particle physics. Gas-discharge lamps filled with argon provide blue light. Argon is also used for the creation of blue and green laser light.

    293. The purest form of Iron is :

    (1) Cast iron 
    (2) Steel
    (3) Pig iron 
    (4) Wrought iron
    Answer:
    293. (4) Wrought iron is an iron alloy with a very low carbon content in contrast to steel, and has fibrous inclusions, known as slag. This is what gives it a “grain” resembling wood, which is visible when it is etched or bent to the point of failure. Wrought iron is tough, malleable, ductile and easily welded. Historically, it was known as “commercially pure iron”; however, it no longer qualifies because current standards for commercially pure iron require a carbon content of less than 0.008 wt%. Wrought iron is the purest form of commercial iron, containing 0.10% to 0.25% of carbon and less than 0.25% of impurities like sulfur, phosphorus, silicon and manganese. Wrought iron is redshort if it contains sulfur in excess quantity. It has sufficient tenacity when cold, but cracks when bent or finished at a red heat. It is therefore useless for welding or forging.

    294. The gas that is used in the manufacture of vanaspati ghee is :

    (1) Oxygen
    (2) Carbon dioxide
    (3) Hydrogen
    (4) Nitrogen
    Answer:
    294. (3) Hydrogenation - to treat with hydrogen - is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst. The process is commonly
    employed to reduce or saturate organic compounds. The largest scale application of hydrogenation is for the processing of vegetable oils (fats to give margarine and related spreads and shortenings). Typical
    vegetable oils are derived from polyunsaturated fatty acids (containing more than one carbon-carbon double bonds). Their partial hydrogenation reduces most but not all, of these carbon-carbon double bonds. Hydrogenation converts liquid vegetable oils into solid or semi-solid fats, such as those present in margarine.

    295. The anode of a dry cell is made up of

    (1) Iron 
    (2) Cadmium
    (3) Zinc 
    (4) Lead
    Answer:
    295. (3) A standard dry cell comprises a zinc anode (negative pole), usually in the form of a cylindrical pot, with a carbon cathode (positive pole) in the form of a central rod. The electrolyte is ammonium chloride in the form of a paste next to the zinc anode. The remaining space between the electrolyte and carbon cathode is taken up by a second paste consisting of ammonium chloride and manganese dioxide, the latter acting as a depolariser.

    296. An example of semiconductor is

    (1) German silver
    (2) Germanium
    (3) Phosphorous
    (4) Arsenic
    Answer:
    296. (2) Purified germanium is a semiconductor, with appearance most similar to elemental silicon. Like silicon, germanium naturally reacts and forms complexes with oxygen in nature. Unlike silicon, it is too reactive to be found naturally on Earth in the free (native) state.

    297. Non-stick kitchenwares are coated with

    (1) PVC 
    (2) Graphite
    (3) Teflon 
    (4) Silicon
    Answer:
    297. (3) Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene that finds
    numerous applications. The best known brand name of PTFE is Teflon. PTFE is used as a non-stick coating for pans and other cookware as it is hydrophobic and possesses fairly high heat resistance.

    298. Gobar gas mainly contains

    (1) Carbon dioxide
    (2) Carbon monoxide
    (3) Hydrogen sulphide
    (4) Methane
    Answer:
    298. (4) Biogas or Gobar gas is produced by the anaerobic digestion or fermentation of biodegradable materials such as biomass, manure, sewage, municipal waste, green waste, plant material, and crops. It comprises primarily methane (CH4) and carbon dioxide (CO2) and may have small amounts of hydrogen sulphide (H2S), moisture and siloxanes.

    299. The chief constituent of vinegar is

    (1) Formic acid
    (2) Acetic acid
    (3) Salycylic acid
    (4) Oxalic acid
    Answer:
    299. (2) Vinegar is a liquid substance consisting mainly of acetic acid (CH3CO2H) and water, the acetic acid being produced through the fermentation of ethanol by acetic acid bacteria. It is today mainly used in the kitchen as a general cooking ingredient, but historically, as the most easily available mild acid, it had a great variety of industrial, medical, and domestic uses.

    300. Sea weeds are important source of

    (1) iron 
    (2) chlorine
    (3) bromine 
    (4) iodine
    Answer:
    300. (4) Seaweed is a source of iodine, necessary for thyroid function and to prevent goitre. However, an excess of iodine is suspected in the heightened cancer risk in Japanese who consume a lot of the plant, and even bigger risks in post-menopausal women.


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