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Chemistry MCQs

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Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination

1.What happens to the weight of Iron, when it rusts?

[A] Increases for long time
[B] Decreases then increases
[C] Increases then decreases
[D] Remains the same

Show Answer
Correct Answer: C [Increases then decreases] Notes:
When iron or any other metal oxidizes, oxygen from the air combines with the iron to make iron oxide or rust. So, weight of the bar increases, due to the increased weight of oxygen which has combined with the iron. Over time, the weight of the iron bar will tend to decrease, due to factors related more to erosion than to chemistry.

2.Which of the following is the correct order of composition of biogas released through anaerobic bio-digester system?

[A] Methane> Carbon dioxide> Nitrogen> Hydrogen
[B] Carbon dioxide> Nitrogen> Methane> Hydrogen
[C] Nitrogen> Hydrogen> Carbon dioxide> Methane
[D] Hydrogen> Nitrogen> Methane> Carbon dioxide

Show Answer
Correct Answer: A [ Methane> Carbon dioxide> Nitrogen> Hydrogen ] Notes:
The correct composition of biogas released through anaerobic bio-digester system is:
Methane (CH4) – 50–75 %
Carbon dioxide (CO2) – 25–50%
Nitrogen (N2) – 0–10%
Hydrogen (H2) – 0–1%
Hydrogen sulphide (H2S) – 0–3%

3.What is the fourth state of matter called?

[A] Solid
[B] Liquid
[C] Gas
[D] Plasma

Show Answer
Correct Answer: D [Plasma] Notes:
The fourth state of matter is called as Plasma. In Plasma, the medium is in the form of positive and negative ions. Plasma occurs in the atmosphere of stars (including the sun) and in discharge tubes.

4.What is Young’s Modulus?

[A] ratio of longitudinal strain to normal stress
[B] product of normal stress of longitudinal strain
[C] ratio of normal stress to longitudinal strain
[D] ratio of normal stress to lateral strain

Show Answer
Correct Answer: C [ratio of normal stress to longitudinal strain] Notes:
Young’s Modulus is defined as the ratio of normal stress to longitudinal strain within limit of proportionality. Y = normal stress/longitudinal strain

5.Which of the following defines the solubility of a solution?

[A] amount of the solvent present in the saturated solution
[B] amount of the solute present in the saturated solution
[C] amount of the solute per amount of solute in the solution
[D] difference of amount of solvent and the amount of solute

Show Answer
Correct Answer: B [amount of the solute present in the saturated solution] Notes:
The amount of the solute present in the saturated solution at a given temperature is called its solubility.

6.Which of the following is an example of colloidal solution?

[A] Milk
[B] Fog
[C] Smoke
[D] All of the above

Show Answer
Correct Answer: D [All of the above] Notes:
Milk, Fog, Smoke, Cheese, Clouds, Mist, Shaving cream, Butter, Jelly, etc. are some of the examples of colloidal solution.

7.Which of the following is also known as Alumina?

[A] AlO2
[B] Al2O3
[C] Al2O4
[D] Al2CO2

Show Answer
Correct Answer: B [Al2O3] Notes:
Alumina is the common name given to aluminum oxide (Al2O3). It is produced from bauxite to get pure aluminium metal.

8.Which of the following is correct about effective nuclear charge experienced by the orbital?

[A] it increases with increase of azimuthal quantum number
[B] it increases with increase of magnetic quantum number
[C] it decreases with increase of azimuthal quantum number
[D] It is same everywhere

Show Answer
Correct Answer: C [it decreases with increase of azimuthal quantum number] Notes:
Because of the screening effect, the net positive charge experienced by the electron from the nucleus is lowered and is known as effective nuclear charge. Effective nuclear charge experienced by the orbital decreases with increase of azimuthal quantum number(l).

9.Which of the following was discovered in Millikan’s oil drop experiment?

[A] Charge on a proton
[B] Charge on an electron
[C] Charge to mass ratio of an electron
[D] Mass of a Hydrogen atom

Show Answer
Correct Answer: B [Charge on an electron] Notes:
R.A. Millikan devised a method known as the oil drop experiment (1906-14), to determine the charge on the electrons. As per the experiment, the charge on the electron was found to be – 1.6 × 10–19 C.

10.What do we call the ratio of number of fission produced by a given generation of neutrons to the number of fission of the preceding generation?

[A] Critical factor
[B] Energy factor
[C] Multiplication factor
[D] Moderation factor

Show Answer
Correct Answer: C [Multiplication factor] Notes:
The multiplication factor is the ratio of the number of fission produced by a given generation of neutrons to the number of fission of the preceding generation.

11.What are the by-products of a hydrogen fuel cell?

[A] Water, heat and ozone
[B] Water and heat
[C] Water and ozone
[D] Heat, methane and Carbon dioxide

Show Answer
Correct Answer: B [Water and heat] Notes:
The only by-products in a fuel cell by combining hydrogen and oxygen are water and heat. They do not emit greenhouse gases or other air pollutants.

12.Which of these polymers are used to produce Butyl-rubber?

[A] butadiene and neoprene
[B] butadiene and styrene
[C] butadiene and acrylonitrile
[D] butadiene and isobutylene

Show Answer
Correct Answer: D [butadiene and isobutylene] Notes:
Butyl-rubber is a synthetic rubber which is obtained as a result of co-polymerization of butadiene and isobutylene.

13.Which of the following polymer is obtained by the condensation reaction between ethylene glycol and terephthalic acid?

[A] Terelene
[B] PMMC
[C] PVC
[D] None of the above

Show Answer
Correct Answer: A [Terelene] Notes:
Terelene is a polymer obtained by the condensation reaction between ethylene glycol and terephthalic acid. It is widely used in making wash and wear fabrics as it has low absorbing power.

14.Which of these two gases are mainly involved in the Haber-Bosch process?

[A] Oxygen, Sulphur
[B] Carbon, Nitrogen
[C] Nitrogen, Hydrogen
[D] Sulphur, Hydrogen

Show Answer
Correct Answer: C [ Nitrogen, Hydrogen ] Notes:
The Haber–Bosch process is the main industrial procedure for the production of ammonia. The process converts atmospheric nitrogen to ammonia by a reaction with hydrogen gas using a metal catalyst under high temperatures and pressures.

15.Which of the following salts of long chain carboxylic acids are the detergents commonly made up of?

[A] ammonium and sulphonate
[B] calcium and magnesium
[C] cobalt and nitrate
[D] None of the above

Show Answer
Correct Answer: A [ammonium and sulphonate] Notes:
Detergents are generally ammonium or sulphonate salts of long chain carboxylic acids. Detergents are usually used to make shampoos and products for cleaning clothes.

16.Rusting of iron takes place due to which of the following processes?

[A] Hydrolysis
[B] Reduction
[C] Carbonation
[D] Oxidation

Show Answer
Correct Answer: D [Oxidation] Notes:
Rusting occurs when iron is exposed to oxygen in air and water or water vapor. Iron plus oxygen plus water vapor gives iron oxide. In areas that have higher humidity, the rusting process takes place faster as the content of moisture in the air is higher.

17.Chewing gum is made from which of the following?

[A] Resin
[B] Polystyrene
[C] Polyvinyl acetate
[D] Latex

Show Answer
Correct Answer: D [Latex] Notes:
Chewing gum was made of a substance called chicle mixed with flavorings. Chicle is a latex sap that comes from the sapodilla tree (native to Central America).

18.Which of the following is not a primary fuel?

[A] Natural Gas
[B] Wood
[C] Kerosene
[D] Coal

Show Answer
Correct Answer: C [Kerosene] Notes:
A primary fuel is that which is used in the same form as it occurs in nature. Kerosene is obtained by the fractional distillation of oil, and hence is a ‘secondary fuel’.

19.What is the common name of ‘Ca(ClO)2’?

[A] Baking Soda
[B] Bleaching Powder
[C] Washing Soda
[D] Baking Powder

Show Answer
Correct Answer: B [Bleaching Powder] Notes:
Calcium hypochlorite is an inorganic compound with formula Ca(ClO)2. It is the main active ingredient of commercial products called bleaching powder, chlorine powder, or chlorinated lime, used for water treatment and as a bleaching agents.

20.Supercooling is cooling of Liquid at which of the following points?

[A] below freezing point
[B] above melting point
[C] melting point
[D] below melting point

Show Answer
Correct Answer: A [below freezing point] Notes:
Supercooling, also known as undercooling, is the process of lowering the temperature of a liquid or a gas below its freezing point without it becoming a solid.

21.Which of these artificial sweeteners has the highest sweetness value?

[A] Saccharin
[B] Sucralose
[C] Aspartame
[D] Alitame

Show Answer
Correct Answer: D [ Alitame] Notes:
Alitame is high potency sweetener having around 2000 times sweetness value in terms of cane sugar. The control of sweetness of food is difficult while using it.

22.Anaemia is caused because of deficiency of which of the following?

[A] Cobalt
[B] Iron
[C] Sodium
[D] Calcium

Show Answer
Correct Answer: B [Iron] Notes:
Anaemia is caused by a shortage of iron in your body. Your bone marrow needs iron to make hemoglobin. Without adequate iron, your body can’t produce enough hemoglobin for red blood cells.

23.In which industry, Potassium Nitrate is used commercially?

[A] Electroplating
[B] Fire Cracker Manufacturing
[C] Leather Industry
[D] Glass Manufacturing

Show Answer
Correct Answer: B [Fire Cracker Manufacturing] Notes:
Firecracker-bccl Gunpowder, which is basically 75% potassium nitrate, 15% charcoal and 10% sulphur, is at the heart of firecrackers.

24.What is Chlorine?

[A] A rare earth element
[B] A halogen
[C] A noble gas
[D] Coinage metal

Show Answer
Correct Answer: B [A halogen] Notes:
Chlorine is a chemical element with the symbol Cl and atomic number 17. It is the second-lightest of the halogens and appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is a yellow-green gas at room temperature.

25.Which among the following is the chemical composition of pearl?

[A] Calcium carbonate
[B] Calcium carbonate and magnesium carbonate
[C] Calcium sulphate
[D] Calcium chloride

Show Answer
Correct Answer: A [Calcium carbonate] Notes:
A pearl is largely made of calcium carbonate, CaCO3, and that compound occurs mostly as platelets having the structure of a naturally-occurring mineral called aragonite.

26.Which of the following chemicals in automobile-exhaust can cause cancer?

[A] Carbon monoxide
[B] Polycyclic hydrocarbons
[C] Lead
[D] Oxides of nitrogen

Show Answer
Correct Answer: A [Carbon monoxide] Notes:
A co-carcinogen is a chemical that promotes the effects of a carcinogen in the production of cancer. A chemical may act as a co-carcinogen even if it does not cause direct DNA damage such as mutation, as long as it can affect a cancer-related pathway.

27.Who gave law of conservation of mass?

[A] Dalton
[B] Boyle
[C] Lavoisier
[D] Berzelius

Show Answer
Correct Answer: C [Lavoisier] Notes:
Antoine Lavoisier (1743 – 1794) was a French chemist who is sometimes referred to as the “father of modern chemistry”. He developed the “law of conservation of mass” which states that for any closed system, the mass of the system must remain constant over time. He also proved that sulfur was an element and named the elements oxygen and hydrogen.

28.Which one of the following metals is used to galvanise iron?

[A] Copper
[B] Lead
[C] Zinc
[D] Mercury

Show Answer
Correct Answer: C [Zinc] Notes:
Galvanization is the process of applying a protective zinc coating to steel or iron, in order to prevent rusting. The term is derived from the name of Italian scientist Luigi Galvani. Although galvanization can be done with electrochemical and electro-deposition processes, the most common method in current use is hot-dip galvanization, in which steel parts are submerged in a bath of molten zinc.

29.Which of the following could be used as fuel in propellant or rockets?

[A] Liquid Hydrogen + Liquid Nitrogen
[B] Liquid Oxygen + Liquid Argon
[C] Liquid Nitrogen + Liquid Oxygen
[D] Liquid Hydrogen + Liquid Oxygen

Show Answer
Correct Answer: D [Liquid Hydrogen + Liquid Oxygen] Notes:
LOX and liquid hydrogen, used in the Space Shuttle orbiter, the Centaur upper stage of the Atlas V, Saturn V upper stages, the newer Delta IV rocket, the H-IIA rocket, and most stages of the European Ariane rockets. Liquid fueled rockets have higher specific impulse than solid rockets and are capable of being throttled, shut down, and restarted. Only the combustion chamber of a liquid fueled rocket needs to withstand high combustion pressures and temperatures and they can be regeneratively cooled by the liquid propellant. For these reasons, most orbital launch vehicles use liquid propellants.The primary performance advantage of liquid propellants is due to the oxidizer.

30.Which of the following contains high content of lead?

[A] Coal
[B] Cooking gas
[C] High octane fuel
[D] Low octane fuel

Show Answer
Correct Answer: C [High octane fuel] Notes:
A high-octane-rated fuel, such gasoline contains lead. Straight-run gasoline is distilled directly from crude oil. Once the leading source of fuel, its low octane rating required lead additives. Most countries have phased out leaded fuel. Different additives have replaced the lead compounds. Such as aromatic hydrocarbons, ethers and alcohol (usually ethanol or methanol).

31.Muddy water is treated with alum in purification process, it is termed as:

[A] emulsification
[B] absorption
[C] adsorption
[D] coagulation

Show Answer
Correct Answer: D [coagulation] Notes:
Natural and wastewater contain small particulates that are suspended in water forming a colloid. These particles carry the same charges, and repulsion prevents them from combining into larger particulates to settle. Historically, dirty water is cleaned by treating with alum, Al2(SO4)3.12 H2O, and lime, Ca(OH)2. The phenomenon is known as coagulation:
Al2(SO4)3.12 H2O Al(aq)3+ + 3SO4(aq)2- + 12H2O
SO4(aq)2- + H2O HSO4(aq)- + OH- (causing pH change)
Ca(OH)2 Ca(aq)2+ + 2 OH- (causing pH change)
The slightly basic water causes Al(OH)3, Fe(OH)3 and Fe(OH)2 to precipitate, bringing the small particulates with them and the water becomes clear.

32.How many isotopes of Hydrogen element are there?

[A] 2
[B] 3
[C] 4
[D] None of the above

Show Answer
Correct Answer: B [3] Notes:
Hydrogen (1H) has three naturally occurring isotopes, sometimes denoted 1H, 2H, and 3H. The 2H (or hydrogen-2) isotope is usually called deuterium, while the 3H (or hydrogen-3) isotope is usually called tritium. The ordinary isotope of hydrogen, with no neutrons, is sometimes called “protium”.

33.What are the components of nucleus of an atom?

[A] Only electrons
[B] Only protons
[C] Both protons and neutrons
[D] Both protons and electrons

Show Answer
Correct Answer: C [Both protons and neutrons] Notes:
The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom. It was discovered in 1911 by Ernest Rutherford based on the 1909 Geiger–Marsden gold foil experiment. Protons and neutrons are bound together to form a nucleus by the nuclear force.

34.Multiplication of equivalent weight and valency of an element is equal to ______:

[A] Density
[B] Relative temperature
[C] Atomic weight
[D] Atomicity

Show Answer
Correct Answer: C [Atomic weight] Notes:
In science, the equivalent weight of a solution is the molecular weight of the solute, or dissolved substance, in grams divided by the valence of the solute. It is expressed as :
Equivalent weight = Atomic weight/Valency
So, Atomic Weight = Equivalent Weight × Valency.

35.Which among the following coal contains 90 per cent of carbon?

[A] Anthracite
[B] Bitumen
[C] Lignite
[D] Peat

Show Answer
Correct Answer: A [Anthracite] Notes:
Coal is a combustible lustrous black or brownish-black sedimentary rock usually occurring in rock strata in layers called coal beds. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure. Hence, anthracite is known to contain 90 per cent of carbon.

36.Quartz is made of:

[A] Calcium Sulphate
[B] Calcium Silicate
[C] Sodium Sulphate
[D] Sodium Silicate

Show Answer
Correct Answer: D [Sodium Silicate] Notes:
Quartz is an abundant mineral in the Earth’s continental crust. It is made up of a continuous framework of SiO4, silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz, several of which are semi-precious gemstones. Most quartz used in microelectronics is produced synthetically. The process involves treating crushed natural quartz with hot aqueous solution of a base such as sodium hydroxide forming sodium silicate.

37.An element that does not occur in nature but can be produced artificially is:

[A] thorium
[B] radium
[C] plutonium
[D] uranium

Show Answer
Correct Answer: C [plutonium] Notes:
Plutonium does not occur in nature. It’s has recently been found but only in traces. Both of these ores are oxided ores, hence need to be reduced in process of extracting metal.

38.The main source of carbon monoxide is:

[A] Industrial process
[B] Fuel combustion
[C] Transportation
[D] Solid waste disposal

Show Answer
Correct Answer: C [Transportation] Notes:
The main source of carbon monoxide is incomplete combustion of fossil fuel.
CO2 + C —> 2CO

39.Which is the purest commercial form of iron?

[A] Pig iron
[B] Steel
[C] Stainless steel
[D] Wrought iron

Show Answer
Correct Answer: D [Wrought iron] Notes:
Wrought iron or malleable weldable form iron is the purest form of commercial iron as it contains the lowest percentage of carbon (0.12-0.25%) and impurities of S, P, Mn and Si in minute amount (about 0.3%). It is made by melting cast iron with scrap iron in a reverberatory furnace lined with Fe2O3 which oxidizes C, Si, P, etc, most of which are then removed by rolling.

40.Bridgmanite is:

[A] A bridge on the river Thames
[B] Name of a game
[C] Earth’s most abundant mineral
[D] Name of a music

Show Answer
Correct Answer: C [Earth’s most abundant mineral] Notes:
Bridgmanite is the accepted name for the mineral silicate perovskite, (Mg,Fe)SiO3, the most common mineral on Earth. It was discovered in Tenham chondrite meteorite, where it associates with another polymorph of MgSiO3 substance – akimotoite.

41.Which of the following has least melting point?

[A] Carbon
[B] Silver
[C] Mercury
[D] Gold

Show Answer
Correct Answer: C [Mercury] Notes:
Among the given options, mercury has the lowest melting point of -38.83 °C. in fact, Mercury has the lowest melting point among all metals and is the only metal that exists as liquid at room temperature. The melting point of Carbon, Silver and Gold is 3550 °C, 961.78 °C and 1064.18 °C respectively.

42.Which of the following is not a natural greenhouse gas?

[A] Carbon dioxide
[B] Nitrogen
[C] Water vapour
[D] Methane

Show Answer
Correct Answer: B [Nitrogen] Notes:
Many greenhouse gases occur naturally in the atmosphere, such as carbon dioxide, methane, water vapor, and nitrous oxide, while others are synthetic. Those that are man-made include the chlorofluoro-carbons (CFCs), hydrofluorocarbons (HFCs) and Perfluorocarbons (PFCs), as well as sulfur hexafluoride (SF6).

43.Carbon footprint can be reduced by:

[A] All are correct
[B] Recycling waste materials
[C] Using energy efficient appliances
[D] Commuting by public transport

Show Answer
Correct Answer: A [All are correct ] Notes:
A carbon footprint is historically defined as “the total sets of greenhouse gas emissions caused by an organization, event, product or person.” The most common way to reduce the carbon footprint of humans is to Reduce, Reuse, Recycle, Refuse. Recycling waste materials, using energy efficient appliances and using public transportation for commutation can all serve to reduce greenhouse gas emissions and, thus, reduce Carbon footprint.

44.What do you understand by the term Espuma?

[A] Foam
[B] Soap
[C] Salt
[D] Calcium

Show Answer
Correct Answer: A [Foam] Notes:
Espuma is a Spanish term for froth or foam, and one that is created specifically with the use of a siphon bottle. Espuma is created mainly with liquid that has air incorporated in it to create froth. This is a specific term, since culinary foams may be attained through other means.

45.What is Zeolite?

[A] Hydrated Aluminosilicate
[B] Hydrated Calcium Sulphate
[C] Dehydrated Aluminosilicate
[D] Dehydrated Calcium Sulphate

Show Answer
Correct Answer: A [Hydrated Aluminosilicate] Notes:
Zeolites are hydrated aluminosilicate minerals made from interlinked tetrahedra of alumina (AlO4) and silica (SiO4). In simpler words, they’re solids with a relatively open, three-dimensional crystal structure built from the elements aluminium, oxygen, and silicon, with alkali or alkaline-Earth metals (such as sodium, potassium, and magnesium) plus water molecules trapped in the gaps between them.

46.When iron rusts, its weight:

[A] decreases
[B] increases
[C] remains the same
[D] first increases and then decreases

Show Answer
Correct Answer: B [increases] Notes:
When iron rusts, oxide compounds are formed due to the interaction between oxygen in the air or in water and the metal. Because of the oxygen atoms binding with the metal, the weight of the metal with rust will increase.

47.Which of the following has the highest penetrating power?

[A] alpha-ray
[B] beta-ray
[C] gama-ray
[D] delta-ray

Show Answer
Correct Answer: C [gama-ray] Notes:
The penetrating power is inversely related to size. Alpha particles, being the largest, penetrate the least. Gamma rays are the most penetrating of the radiations. They are highly energetic waves and are poor at ionising other atoms or molecules being neutral.

48.Chernobyl disaster is the result of pollution by:

[A] Oil spill
[B] Acid rain
[C] Carbon dioxide
[D] Radioactive waste

Show Answer
Correct Answer: D [Radioactive waste] Notes:
Chernobyl disaster was a catastrophic nuclear accident that occurred on 26 April 1986 at the Chernobyl Nuclear Power Plant in the city of Pripyat, then located in the Ukrainian USSR. An explosion and fire released large quantities of radioactive particles into the atmosphere, which spread over much of the western USSR and Europe containing monazite.

49.Which of the following is used to make light weight, but strong plastic?

[A] Nylon
[B] Polythene
[C] Polyvinyl Chloride
[D] Methyl Methacrylate

Show Answer
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.What is the general formula of alkenes?

[A] CnH(2n)
[B] CnH(2n+2)
[C] CnH(2n–2)
[D] CnH(2n–1)

Show Answer
Correct Answer: A [CnH(2n)] Notes:
The generic formula for alanes is CnH2n+2, where n is the number identified by the prefix. Alkenes have the formula CnH2N. The general formula means that the number of hydrogen atoms in an alkene is double the number of carbon atoms. For example, ethene is C2H4 and propene is C3H6.

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