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SSC > Chemistry

Explore popular questions from Chemistry for SSC. This collection covers Chemistry previous year SSC questions hand picked by experienced teachers.

Q 1.

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The gas used for filling weather balloons is

helium

B

hydrogen

C

air

D

nitrogen

Explanation

A balloon is an inflatable flexible bag filled with a gas, such as helium, hydrogen, nitrous oxide, oxygen, or air. Modern balloons can be made from materials such as rubber, latex, polychloroprene, or a nylon fabric, while some early balloons were made of dried animal bladders, such as the pig bladder. Some balloons are used for decorative purposes, while others are used for practical purposes such as meteorology, medical treatment, military defense, or transportation. A balloon's properties, including its low density and low cost, have led to a wide range of applications. Because of the non combustible property of the helium gas it is widely used in weather balloons rather than hydrogen gas which is highly combustible.

Q 2.

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Hydrogen is not found in atmosphere because

A

it is highly inflammable

it is the lightest gas

C

it is absorbed by plants

D

it immediately combines with oxygen to form water

Explanation

Hydrogen is a chemical element with symbol H and atomic number 1. With an average atomic weight of 1.00794 u (1.007825 u for hydrogen-1), hydrogen is the lightest element and its monatomic form (HI) is the most abundant chemical substance, constituting roughly 75% of the Universe's baryonic mass. Nonremnant stars are mainly composed of hydrogen in its plasma state. Air is the name given to the atmosphere used in breathing and photosynthesis. Dry air contains roughly (by volume) 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1%. Naturally occurring atomic hydrogen is rare on Earth because hydrogen readily forms covalent compounds with most elements and is present in the water molecule and in most organic compounds.

Q 3.

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Who discovered the atom bomb?

A

Madam Curie

B

Pierre Curie

Otto Hahn

D

Albert Einstein

Explanation

Otto Hahn, (8 March, 1879 - 28 July, 1968) was a German chemist and Nobel laureate, a pioneer in the fields of radioactivity and radiochemishy. He is regarded as "the father of nuclear chemistry". On 15 November 1945 the Royal Swedish Academy of Sciences announced that Hahn had been awarded the 1944 Nobel Prize in Chemistry "for his discovery of the fission of heavy atomic nuclei." Otto Hahn received many governmental honours and academic awards from all over the world for his scientific work. He was elected member or honorary member of 45 Academies and scientific societies (among them the Physical Society, the University College and the Royal Society in London (1957) and the Academies in Allahabad (India), Bangalore (India), Boston (USA), Bucharest, Copenhagen, Helsinki, Lisbon, Madrid, Rome, Stockholm, Vienna) and received 37 of the highest national and international orders and medals.

Q 4.

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Which one of the following organic compounds has fruity smell?

A

Alcohol

B

Aldehyde

Ester

D

Ether

Explanation

Esters are common in organic chemistry and biological materials, and often have a characteristic pleasant, fruity odour. This leads to their extensive use in the fragrance and flavor industry. Ester bonds are also found in many polymers. Esterification is the general name for a chemical reaction in which two reactants (typically an alcohol and an acid) form an ester as the reaction product. Esters are widespread in nature and are widely used in industry. In nature, fats are, in general, triesters derived from glycerol and fatty acids. Esters are responsible for the aroma of many fruits, including apples, durians, pears, bananas, pineapples, and strawberries.

Q 5.

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Polythene is polymer of

Ethylene

B

Propylene

C

Acetylene

D

Aniline

Explanation

The ingredient or monomer is ethylene (IUPAC name ethene). It has the formula {tex}C_{2}H_{4}{/tex}, consisting of a pair of {tex}CH_{2}{/tex} groups connected by a double bond. Because the catalysts are highly reactive, the ethylene must be of high purity. Typical specifications are <5 ppm for water, oxygen, as well as other alkenes. Acceptable contaminants include {tex}N_2{/tex}, ethane (common precursor to ethylene), and methane. Ethylene is usually produced from petrochemical sources, but also is generated by dehydration of ethanol. Polyethylene (abbreviated PE) or polythene (IUPAC name polyethene or poly (methylene)) is the most common plastic. Its primary use is within packaging (plastic bag, plastic films, geomembranes, containers including bottles, etc.).

Q 6.

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For determination of the age of which among the following is carbon dating method used?

A

Fossils

B

Rocks

C

Trees

1 & 2 above

Explanation

Radiocarbon dating (usually referred to as simply carbon dating) is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 ({tex}^{14} C{/tex}) to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e., uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" (BP), with "present" defined as CE 1950. Such raw ages can be calibrated to give calendar dates. One of the most frequent uses of radiocarbon dating is to estimate the age of organic remains from archaeological sites. When plants fix atmospheric carbon dioxide (C0{tex}_2{/tex}) into organic matter during photosynthesis they incorporate a quantity of {tex}^{14} C{/tex} that approximately matches the level of this isotope in the atmosphere. After plants die or they are consumed by other organisms (for example, by humans or other animals), the accumulation of {tex}^{14} C{/tex} fraction stops and the material declines at a fixed exponential rate due to the radioactive decay of {tex}^{14} C{/tex}.

Q 7.

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A substance which readily forms colloidal solution in contact with water is called

A

Extrinsic colloid

B

Associated colloid

C

Hydrophobic colloid

Hydrophilic colloid

Explanation

A colloidal dispersion in which the dispersed particles are more or less liquid and exert a certain attraction on and absorb a certain quantity of the fluid in which they are suspended is called as hydrophilic colloid. Molecules of a hydrophilic colloid have an affinity for water molecules and when dispersed in water become hydrated. Hydrated colloids swell and increase the viscosity of the system, thereby improving stability by reducing the interaction between particles and their tendency to settle. They may also possess a net surface electrical charge. The charge sign depends on the chemical properties of the colloid and the pH of the system. The presence of a surface charge produces repulsion of the charged particles and thus reduces the likelihood that the particles will adhere to one another and settle. Some examples of hydrophilic colloids used in pharmacy are acacia, methylcellulose, and proteins, such as gelatin and albumin.

Q 8.

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When formaldehyde and potassium hydroxide are heated, we get

A

Acetylene

Methyl alcohol

C

Methane

D

Ethyl formate

Explanation

When formaldehyde and potassium hydroxide are heated,we get methyl alcohol and formic acid, it is cannizzaro reaction. The Cannizzaro reaction, named after its discoverer StanislaoCannizzaro, is a chemical reaction that involves the base-induced disproportionation of an aldehyde. Cannizzaro first accomplished this transformation in 1853, when he obtained benzyl alcohol and potassium benzoate from the treatment of benzaldehyde with potash (potassium carbonate). More typically, the reaction would be conducted with sodium or potassium hydroxide. The oxidation product is a salt of a carboxylic acid and the reduction product is an alcohol.

Q 9.

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When conc. H2SO4 is added to dry KNO3, brown fumes are evolved. These fumes are due to

A

SO3

B

SO2

NO2

D

N2O

Explanation

when concentrated hydrosulphuric acid is added to dry potassium nitrate brown fumes are evolved and these fumes are evolved due to the formation of nitrogen dioxide. Nitrogen dioxide is the chemical compound with the formula NO{tex}_2{/tex}. It is one of several nitrogen oxides. NO{tex}_2{/tex} is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year. This reddish-brown toxic gas has a characteristic sharp, biting odour and is a prominent air pollutant. Nitrogen dioxide is a paramagnetic and bent molecule.

Q 10.

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The polymer used in making plastic crockery is

A

Decron

B

Nylon

C

Bakelite

Melamine

Explanation

Melamine-formaldehyde resin or melamine is used in the manufacture of plastic crockery. Melamine resin or melamine formaldehyde (also shortened to melamine) is a hard, thermosetting plastic material made from melamine and formaldehyde by polymerization. Melamine resin is often used in kitchen utensils and plates (such as Melmac). Melamine resin utensils and bowls are not microwave safe. As with all thermosetting materials, melamine resin cannot be melted and, therefore, cannot be recycled through melting.

Q 11.

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Vulcanization of rubber is carried out by adding

Sulphur

B

Carbon

C

Ozone

D

Phosphorus

Explanation

Vulcanization is a chemical process for converting rubber or related polymers into more durable materials via the addition of sulfur or other equivalent "curatives" or "accelerators". These additives modify the polymer by forming crosslinks (bridges) between individual polymer chains. Vulcanized materials are less sticky and have superior mechanical properties. A vast array of products are made with vulcanized rubber including tires, shoe soles, hoses, and hockey pucks. The process is named after Vulcan, Roman god of fire. Hard vulcanized rubber is sometimes sold under the brand names ebonite or vulcanite, and is used to make hard articles such as bowling balls and saxophone mouth pieces.

Q 12.

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Preparation of 'Dalda or Vanaspati' ghee from vegetable oil utilizes the following process :

A

Hydrolysis

B

Oxidation

Hydrogenation

D

Ozonolysis

Explanation

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. Hydrogenation - to treat with hydrogen - is a chemical reaction between molecular hydrogen (H{tex}_2{/tex}) and another compound or element, usually in the presence of a catalyst. The process is commonly employed to reduce or saturate organic compounds. Hydrogenation typically constitutes the addition of pairs of hydrogen atoms to a molecule, generally an alkene.

Q 13.

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Smoke is formed due to

solid dispersed in gas

B

solid dispresed in liquid

C

gas dispresed in solid

D

gas dispersed in gas

Explanation

Smoke is a collection of airborne solid and liquid particulates and gases emitted when a material undergoes combustion or pyrolysis, together with the quantity of air that is entrained or otherwise mixed into the mass. It is commonly an unwanted by-product of fires (including stoves, candles, oil lamps, and fireplaces), but may also be used for pest control (cf. fumigation), communication (smoke signals), defensive and offensive capabilities in the military (smokescreen), cooking (smoked salmon), or smoking (tobacco, cannabis, etc.). Smoke inhalation is the primary cause of death in victims of indoor fires. The smoke kills by a combination of thermal damage, poisoning and pulmonary irritation caused by carbon monoxide, hydrogen cyanide and other combustion products.

Q 14.

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What is the principal ore of aluminium ?

A

Dolomite

B

Copper

C

Lignite

Bauxite

Explanation

Bauxite is an aluminium ore and is the main source of aluminium. This form of rock consists mostly of the minerals gibbsite ,boehmite , and diaspore , in a mixture with the two iron oxides goethite and hematite, the clay mineral kaolinite, and small amounts of anatase Ti0{tex}_2{/tex}. Bauxite was named after the village Les Baux in southern France, where it was first recognised as containing aluminium and named by the French geologist Pierre Berthier in 1821. Lateritic bauxites (silicate bauxites) are distinguished from karst bauxite ores (carbonate bauxites). The early discovered carbonate bauxites occur predominantly in Europe and Jamaica above carbonate rocks (limestone and dolomite), where they were formed by lateritic weathering and residual accumulation of intercalated clays or by clay dissolution residues of the limestone.

Q 15.

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Which one of the following is extensively used for sterilizing water ?

Bleaching powder

B

Alum

C

Borax powder

D

Soda powder

Explanation

Bleaching powder is extensively used in sterilizing water. Calcium hypochlorite is a chemical compound with formula Ca(OCl){tex}_2{/tex}- It is widely used for water treatment and as a bleaching agent (bleaching powder). This chemical is considered to be relatively stable and has greater available chlorine than sodium hypochlorite (liquid bleach). Calcium hypochlorite is a yellow white solid which has a strong smell of chlorine. It is not highly soluble in water, and is more preferably used in soft to medium-hard water. It has two forms: a dry form and a hydrated form. The hydrated form is safer to handle.

Q 16.

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German silver used for making utensils is an alloy of

A

copper, silver, nickel

copper, zinc, nickel

C

copper, zinc, aluminium

D

copper, nickel, aluminium

Explanation

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.

Q 17.

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

24 carats

B

99.6 carats

C

91.6 carats

D

22 carats

Explanation

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.

Q 18.

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An emulsion is a colloid of a

A

gas in a liquid

liquid in a liquid

C

liquid in a gas

D

gas in a solid

Explanation

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.

Q 19.

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

A

Copper

B

Nickel

Silver

D

Zinc

Explanation

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.

Q 20.

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

Carbon Monoxide

B

Methane

C

Carbon dioxide

D

Ozone gas

Explanation

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.

Q 21.

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

Carbon dioxide

B

Chloro fluorocarbon

C

Carbon monoxide

D

Freon

Explanation

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 C0{tex}_2{/tex} the AF over the last 50 years (1956-2006) has been increasing at 0.25 ± 0.21%/year.

Q 22.

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Ruby and sapphire are oxides of

A

copper

B

tin

C

iron

aluminium

Explanation

Aluminium forms one stable oxide, known by its mineral name corundum. Sapphire and ruby are impure corundum contaminated with trace amounts of other metals. Corundum is a crystalline form of aluminium oxide (A1203) with traces of iron, titanium and chromium. It is a rock-forming mineral. It is one of the naturally clear transparent materials, but can have different colours when impurities are present. Transparent specimens are used as gems, called ruby if red and padparadscha if pink-orange. All other colours are called sapphire, e.g., "green sapphire" for a green specimen. Because of corundum's hardness (pure corundum is defined to have 9.0 Mohs), it can scratch almost every other mineral. It is commonly used as an abrasive, on everything from sandpaper to large machines used in machining metals, plastics, and wood. Some emery is a mix of corundum and other substances, and the mix is less abrasive, with an average hardness near 8.0.

Q 23.

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The major constituent of gobar gas is

A

Carbon dioxide

Methane

C

Butane

D

Isobutane

Explanation

Gobar Gas (Methane) is generated by the decomposition of organic cow dung. It consists of 55-65% methane, 30-35% carbon dioxide, with some hydrogen, nitrogen and other traces. The composition of biogas varies depending upon the origin of the anaerobic digestion process. Landfill gas typically has methane concentrations around 50%. Advanced waste treatment technologies can produce biogas with 55-75% methane, which for reactors with free liquids can be increased to 80-90% methane using in-situ gas purification techniques. As-produced, biogas also contains water vapor. The fractional volume of water vapor is a function of biogas temperature; correction of measured gas volume for both water vapor content and thermal expansion is easily done via a simple mathematic algorithm which yields the standardized volume of dry biogas.

Q 24.

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Zinc sulphide is commonly used as

A

fungicide

B

herbicide

rodenticide

D

deodorant

Explanation

Rodenticides are a category of pest control chemicals intended to kill rodents. Metal phosphides have been used as a means of killing rodents and are considered single-dose fast acting rodenticides (death occurs commonly within 1-3 days after single bait ingestion). A bait consisting of food and a phosphide (usually zinc phosphide) is left where the rodents can eat it. The acid in the digestive system of the rodent reacts with the phosphide to generate the toxic phosphine gas. This method of vermin control has possible use in places where rodents are resistant to some of the anticoagulants, particularly for control of house and field mice; zinc phosphide baits are also cheaper than most second-generation anticoagulants, so that sometimes, in the case of large infestation by rodents, their population is initially reduced by copious amounts of zinc phosphide bait applied, and the rest of population that survived the initial fast-acting poison is then eradicated by prolonged feeding on anticoagulant bait.

Q 25.

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The iron ore which contains 72% of iron is :

Magnetite

B

Limonite

C

Haematite

D

Siderite

Explanation

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.