Chemistry GK Questions Quiz-9

Chemistry GK Questions Quiz-9

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

    161. Which one of the following acids is used in battery ?

    (1) Hydrochloric acid
    (2) Hydrofluoric acid
    (3) Sulphuric acid
    (4) Sulphurous acid
    Answer:
    161. (3) Battery is a device consisting of one or more electrochemical cells that convert stored chemical
    energy into electrical energy. Possessing different chemical properties, the sulfuric acid has a wide range of applications including domestic acidic drain cleaner, electrolyte in lead-acid batteries and various cleaning agents. Sulfuric acid (sulphuric acid) is a highly corrosive strong mineral acid with the molecular formula H2SO4. It is a colourless to slightly yellow viscous liquid which is soluble in water at all concentrations. Sometimes, it may be dark brown as dyed during industrial production process in order to alert people to its hazards.

    162. The major constituent of air is

    (1) nitrogen 
    (2) carbon dioxide
    (3) oxygen 
    (4) hydrogen
    Answer:
    162. (1) Depending on various geographical locations these may change, but for the most part air is made up of 78% nitrogen (N2), 21% oxygen (O2), and trace amounts of carbon dioxide (CO2), methane (CH4 hydrogen (H2), argon (Ar) and helium (He). The CO2, CH4, H2, Ar, and He, when combined together, make up about 1% of our air. Nitrogen is a chemical element with symbol N and atomic number 7. Elemental nitrogen is a colourless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.09% by volume of Earth’s atmosphere. Nitrogen is a common element in the universe, estimated at about seventh in total abundance in our galaxy and the Solar System. Its occurrence there is thought to be entirely due to synthesis by fusion from carbon and hydrogen in supernovas.

    163. Cream gets separated out of milk when it is churned. This is due to

    (1) gravitational force
    (2) centripetal force
    (3) centrifugal force
    (4) frictional force
    Answer:
    163. (3) During the churning of buttermilk, many particles of curd undergo rotatory motion. Then the particles with less weight experience more centripetal force and hence those particles accumulate at the center. Heavier particles experience more centrifugal force and so they are forced to the walls of the container away from the centre. Hence, light butter particles accumulate at the center due to centripetal force and heavy buttermilk particles thrown away from the center to the walls of the container due to the centrifugal force. In this way butter cream gets separated from the butter milk. Similarly butter can also be taken from the raw milk using the similar procedure. Similar method is used to know the percentage of butter existing in the milk.

    164. Rusting of iron takes place due to

    (1) oxidation 
    (2) carbonation
    (3) exfoliation 
    (4) corrosion
    Answer:
    164. (1) The rusting of iron is an electrochemical process that begins with the transfer of electrons from iron to oxygen. The rate of corrosion is affected by water and accelerated by electrolytes, as illustrated by the effects of road salt on the corrosion of automobiles. 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. Iron metal is relatively unaffected by pure water or by dry oxygen. The conversion of the passivating iron oxide layer to rust results from the combined action of two agents, usually oxygen and water.

    165. German silver used for making utensils is an alloy of

    (1) copper, silver, nickel
    (2) copper, zinc, nickel
    (3) copper, zinc, aluminium
    (4) copper, nickel, aluminium
    Answer:
    165. (2) Nickel silver, also known as German silver, Argentan, new silver, nickel brass, albata, alpacca,
    or electrum, is a copper alloy with nickel and often zinc. The usual formulation is 60% copper, 20% nickel and 20% zinc. Nickel silver is named for its silvery appearance, but it contains no elemental silver unless plated. The name “German silver” refers to its development by 19th-century German metalworkers in imitation of the Chinese alloy known as paktong. Nickel silver first became popular as a base metal for silver-plated cutlery and other silverware, notably the electroplated wares called EPNS (electro-plated nickel silver). It is used in zippers, better-quality keys, costume jewellery, for making musical instruments (e.g., cymbals, saxophones), and is preferred for the track in electrically powered model railway layouts, as its oxide is conductive. It is widely used in the production of coins.

    166. The purity of gold is expressed in carats. The purest form of gold is

    (1) 24 carats 
    (2) 99.6 carats
    (3) 91.6 carats
    (4) 22 carats
    Answer:
    166. (1) Gold is a dense, soft, shiny, malleable and ductile metal. Gold has a bright yellow colour and luster traditionally considered attractive, which it maintains without oxidizing in air or water. The metal therefore occurs often in free elemental (native) form, as nuggets or grains in rocks, in veins and in alluvial deposits. Less commonly, it occurs in minerals as gold compounds, usually with tellurium. Pure gold is too soft for day-to-day monetary use and is typically hardened by alloying with copper, silver or other base metals. The gold content of alloys is measured in carats (k). Pure gold is designated as 24k.Because of the softness of pure (24k) gold, it is usually alloyed with base metals for use in jewelry, altering its hardness and ductility, melting point, colour and other properties. Alloys with lower caratage, typically 22k, 18k, 14k or 10k, contain higher percentages of copper, or other base metals or silver or palladium in the alloy. Copper is the most commonly used base metal, yielding a redder colour.

    167. Petroleum consists of a mixture of

    (1) Carbohydrates
    (2) Carbonates
    (3) Hydrocarbons
    (4) Carbides
    Answer:
    167. (3) Petroleum ( petroleum, from Latin: ‘petra’ (rock) + Latin: oleum (oil) or crude oil is a naturally occurring flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth’s surface. Petroleum is recovered mostly through oil drilling. It is refined and separated, most easily by boiling point, into a large number of consumer products, from petrol (or gasoline) and kerosene to asphalt and chemical reagents used to make plastics and pharmaceuticals. Petroleum is used in manufacturing a wide variety of materials, and it is estimated that the world consumes about 88
    million barrels each day. hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. The majority of hydrocarbons found naturally occur in crude oil, where decomposed organic matter provides an abundance of carbon and hydrogen which, when bonded, can catenate to form seemingly limitless chains.

    168. The lustre of the metals is because of

    (1) high density, due to closed packing of atoms
    (2) high polish
    (3) reflection of light due to the presence of free electrons
    (4) absorption of light due to the presence of cavities
    Answer:
    168. (3) Lustre (or luster) is the way light interacts with the surface of a crystal, rock, or mineral. The word traces its origins back to the latin lux, meaning “light”, and generally implies radiance, gloss, or brilliance. Metals in general have high electrical conductivity, high thermal conductivity, and high density. Typically they are malleable and ductile, deforming under stress without cleaving. In terms of optical properties, metals are shiny and lustrous. Sheets of metal beyond a few micrometres in thickness appear opaque, but gold leaf transmits green light. Metallic (or splendant) minerals have the lustre of polished metal, and with ideal surfaces will work as a reflective surface. Examples include galena, pyrite and magnetite.

    169. One of the following is used to dissolve noble metals. That is

    (1) Nitric acid
    (2) Hydrochloric acid
    (3) Sulphuric acid
    (4) Aqua ragia
    Answer:
    169. (4) Aqua regia (“royal water”), aqua regis ( “king’s water”), or nitro-hydrochloric acid is a highly corrosive mixture of acids, a fuming yellow or red solution. The mixture is formed by freshly mixing concentrated nitric acid and hydrochloric acid, usually in a volume ratio of 1:3. It was named so because it can dissolve the so-called royal or noble metals, gold and platinum. However, titanium, iridium, ruthenium, tantalum, osmium, rhodium and a few other metals are capable of withstanding its corrosive properties. Aqua regia is primarily used to produce chloroauric acid, the electrolyte in the Wohlwill process. This process is used for refining highest quality (99.999%) gold. Aqua regia is also used in etching and in specific analytic procedures. It is also used in some laboratories to clean glassware of organic compounds and metal particles. While local regulations may vary, aqua regia may be disposed of by careful neutralization, before being poured down the sink. If there is contamination
    by dissolved metals, the neutralized solution should be collected for disposal.

    170. An emulsion is a colloid of a

    (1) gas in a liquid
    (2) liquid in a liquid
    (3) liquid in a gas
    (4) gas in a solid
    Answer:
    170. (2) An emulsion is a mixture of two or more liquids that are normally immiscible (nonmixable or
    unblendable). Emulsions are part of a more general class of two-phase systems of matter called colloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion should be used when both the dispersed and the continuous phase are liquids. In an emulsion, one liquid (the dispersed phase) is dispersed in the other (the continuous phase). Examples of emulsions include vinaigrettes, milk, mayonnaise, and some cutting fluids for metal working. The photo-sensitive side of photographic film is also an example of a colloid. The word “emulsion” comes from the Latin word for “to milk”, as milk is (among other things) an emulsion of milk fat and water. Two liquids can form different types of emulsions. As an example, oil and water can form, firstly, an oil-inwater emulsion, where the oil is the dispersed phase, and water is the dispersion medium.

    171. Percentage of carbon in steel ranges from

    (1) 0.1 to 1.5 
    (2) 1.5 to 3.0
    (3) 3.0 to 4.0 
    (4) 4.0 to 6.0
    Answer:
    171. (1) Steel is an alloy made by combining iron and other elements, the most common of these being carbon. When carbon is used, its content in the steel is between 0.2% and 2.1% by weight, depending on the grade. Other alloying elements sometimes used are manganese, chromium, vanadium and tungsten. Carbon and other elements act as a hardening agent, preventing dislocations in the iron atom crystal lattice from sliding past one another. Varying the amount of alloying elements and the form of their presence in the steel (solute elements, precipitated phase) controls qualities such as the hardness, ductility, and tensile strength of the resulting steel. Steel with increased carbon content can be made harder and stronger than iron, but such steel is also less ductile than iron. Alloys with a higher than 2.1% carbon content are known as cast iron because of their lower melting point and good castability.

    172. Which of the following is not present in German-silver?

    (1) Copper 
    (2) Nickel
    (3) Silver 
    (4) Zinc
    Answer:
    172. (3) Nickel silver, also known as German silver, Argentan, new silver, nickel brass, albata, alpacca,
    or electrum, is a copper alloy with nickel and often zinc. The usual formulation is 60% copper, 20% nickel and 20% zinc. Nickel silver is named for its silvery appearance, but it contains no elemental silver unless plated. The name “German silver” refers to its development by 19th-century German metalworkers in imitation of the Chinese alloy known as paktong. Nickel silver first became popular as a base metal for silver-plated cutlery and other silverware, notably the electroplated wares called EPNS (electro-plated nickel silver). It is used in zippers, better-quality keys, costume jewellery, for making musical instruments (e.g., cymbals, saxophones), and is preferred for the track in electrically powered model railway layouts, as its oxide is conductive. It is widely used in the production of coins.

    173. The major harmful gas emitted by automobile vehicles which causes air pollution is

    (1) Carbon Monoxide
    (2) Methane
    (3) Carbon dioxide
    (4) Ozone gas
    Answer:
    173. (1) Carbon monoxide is the major harmful gas emitted by the automobile vehicles which causes air pollution. Carbon monoxide (CO) - A product of incomplete combustion, carbon monoxide reduces the blood’s ability to carry oxygen; overexposure (carbon monoxide poisoning) may be fatal. Carbon Monoxide poisoning is a major killer. Carbon monoxide is a temporary atmospheric pollutant in some urban areas, chiefly from the exhaust of internal combustion engines (including vehicles, portable and back-up generators, lawn mowers, power washers, etc.), but also from incomplete combustion of various other fuels (including wood, coal, charcoal, oil, paraffin, propane, natural gas, and trash). Carbon monoxide is, along with aldehydes, part of the series of cycles of chemical reactions that form photochemical smog.

    174. Which one of the following is a major green house gas?

    (1) Carbon dioxide
    (2) Chloro fluorocarbon
    (3) Carbon monoxide
    (4) Freon
    Answer:
    174. (1) 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). Atmospheric concentrations of greenhouse gases are determined by the balance between sources (emissions of the gas from human activities and natural systems) and sinks (the removal of the gas from the atmosphere by conversion to a different chemical compound). The proportion of an emission remaining in the atmosphere after a specified time is the “Airborne fraction” (AF). More precisely, the annual AF is the ratio of the atmospheric increase in a given year to that year’s total emissions. For CO2 the AF over the last 50 years (1956–2006) has been increasing at 0.25 ± 0.21%/year.

    175. Pasteurisation is the process in which milk is heated to

    (1) 60°C for 10 minutes
    (2) 63° C for 20 minutes
    (3) 63°C for 30 minutes
    (4) 72°C for 10 minutes
    Answer:
    175. (3) Pasteurization (or pasteurisation) is a process of heating a food, which is usually a liquid, to a specific temperature for a predefined length of time and then immediately cooling it after it is removed from the heat. This process slows spoilage due to microbial growth in the food. Unlike sterilization, pasteurization is not intended to kill all micro-organisms in the food. Instead, it aims to reduce the number of viable pathogens so they are unlikely to cause disease (assuming the pasteurized product is stored as indicated and is consumed before its expiration date). Commercial-scale sterilization of food is not common because it adversely affects the taste and quality of the product. Certain foods, such as dairy products, may be superheated to ensure pathogenic microbes are destroyed. A less conventional but US FDA-legal alternative (typically for home pasteurization) is to heat milk at (63 degree C) for 30 minutes.

    176. The freezer in a refrigerator is fitted near the top

    (1) to keep it away from hot compressor which is nearer to the bottom
    (2) because of convenience
    (3) it facilitates convection currents
    (4) to minimise power consumption
    Answer:
    176. (3) The freezer in a refrigerator is fitted near the top so that it can cool the whole interior by setting up convection currents. Most household freezers maintain temperatures from (-23 to -18 degree C),
    although some freezer-only units can achieve (-34 degree C), and lower. Refrigerators generally do not
    achieve lower than (-23 degree C), since the same coolant loop serves both compartments: Lowering the freezer compartment temperature excessively causes difficulties in maintaining above-freezing temperature in the refrigerator compartment. Domestic freezers can be included as a separate compartment in a refrigerator, or can be a separate appliance. Domestic freezers are generally upright units resembling refrigerators, or chests (resembling upright units laid on their backs). Many upright modern freezers come with an ice dispenser built into their door.

    177. The chemical name of ‘Common salt’ is

    (1) Sodium chloride
    (2) Sodium nitrate
    (3) Ammonium chloride
    (4) Calcium chloride
    Answer:
    177. (1) Sodium chloride, also known as salt, common salt, table salt or halite, is an ionic compound with the formula NaCl, representing equal proportions of sodium and chloride. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms. As the major ingredient in edible salt, it is commonly used as a condiment and food preservative. In solid sodium chloride, each ion is surrounded by six ions of the opposite charge as expected on electrostatic grounds. The surrounding ions are located at the vertices of a regular octahedron. In the language of close-packing, the larger chloride ions are arranged in a cubic array whereas the smaller sodium ions fill all the cubic gaps (octahedral voids) between them.

    178. Denatured spirit is ethanol mixed with

    (1) Petrol 
    (2) Kerosene
    (3) Water 
    (4) Pyridine
    Answer:
    178. (4) Denatured alcohol or methylated spirits is ethanol that has additives to make it undrinkable (poisonous), to discourage recreational consumption. In some cases it is also dyed. Denatured alcohol is used as a solvent and as fuel for spirit burners and camping stoves. Because of the diversity of industrial uses for denatured alcohol, hundreds of additives and denaturing methods have been used. The main additive has traditionally been 10% methanol, giving rise to the term “methylated spirit.” Other typical additives include isopropyl alcohol, acetone, methyl ethyl ketone, methyl isobutyl ketone, and denatonium. Completely denatured alcohol must be made in accordance with the following formulation: with every 90 parts by volume of alcohol mix 9.5 parts by volume of wood naphtha or a substitute and 0.5 parts by volume of crude pyridine, and to the resulting mixture add mineral naphtha (petroleum oil) in the proportion of 3.75 litres to every 1000 litres of the mixture and synthetic organic dyestuff (methyl violet) in the proportion of 1.5 grams to every 1000 litres of the mixture.

    179. The most abundant inert gas in the atmosphere is

    (1) Helium 
    (2) Neon
    (3) Argon 
    (4) Krypton
    Answer:
    179. (3) Argon is the third most common gas in the Earth’s atmosphere, at 0.93% (9,300 ppm), making it approximately 23.8 times as abundant as next most common atmospheric gas, carbon dioxide (390 ppm), and more than 500 times as abundant as the next most common noble gas, neon (18 ppm). Nearly all of this argon is radiogenic argon-40 derived from the decay of potassium-40 in the Earth’s crust. In the universe, argon-36 is by far the most common argon isotope, being the preferred argon isotope produced by stellar nucleosynthesis in supernovas. We find the inert gases argon (9,340 ppmv), neon (18.18 ppmv) and helium (5.24 ppmv) in the earth’s atmosphere. Note that we use ppmv here to mean parts per million by volume.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.

    180. Which metal is extracted from sea water?

    (1) Potassium 
    (2) Magnesium
    (3) Aluminium 
    (4) Beryllium
    Answer:
    180. (2) The metal is now mainly obtained by electrolysis of magnesium salts obtained from brine.
    Commercially, the chief use for the metal is as an alloying agent to make aluminium-magnesium alloys,
    sometimes called “magnalium” or “magnelium”. Since magnesium is less dense than aluminium, these alloys are prized for their relative lightness and strength. Magnesium is the fourth most common element in the Earth as a whole (behind iron, oxygen and silicon), making up 13% of the planet’s mass and a large fraction of the planet’s mantle. The relative abundance of magnesium is related to the fact that it is easily built up in supernova stars from a sequential addition of three helium nuclei to carbon (which in turn is made from three helium nuclei). Due to magnesium ion’s high solubility in water, it is the third most abundant element dissolved in seawater.


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