Some basic concepts of chemistry mcq with explanation

In the view of Competative exam Chemistry is considered to be the most scoring subject. This is one of the easiest scoring subjects, it is often ignored and undermined a subject. But if you want to get an edge over others, here is a tip, Chemistry mcq concepts for any competitive exam. Chemistry demands the attention of students in understanding reactions and concrete basic understanding but once done it only gets easier from there.

This article leads you to Fifty of solved MCQ on a variety of Chemistry topics important from Competative exam standpoint. In below Discussion different topics with corresponding direct links, facilitating smooth learning and search experience.

Q.1) What is “milk of magnesia” chemically?

(1) Magnesium carbonate

(2) Sodium bicarbonate

(3) Calcium hydroxide

(4) Magnesium hydroxide

Correct Answer – (4) Magnesium hydroxide

Explanation: agnesium hydroxide is an inorganic compound with the chemical formula Mg(OH)2. As a suspension in water, it is often called milk of magnesia because of its milk-like appearance. The solid mineral form of magnesium hydroxide is known as brucite.

Q.2) The acid used in lead storage cells is –

(1) phosphoric acid

(2) hydrochloric acid

(3) nitric acid

(4) sulphuric acid

Correct Answer – (4) sulphuric acid

Explanation: Dilute sulfuric acid (H2SO4) serves as the electrolyte in a lead storage battery. The electrodes of the cells in a lead storage battery consist of lead grids. The openings of the anodic grid is filled with spongy (porous) lead. The opehings of the cathodic grid is filled with lead dioxide (PBO2).

Q.3) Milk tastes sour when kept in the open for sometime due to the formation of –

(1) lactic acid

(2) citric acid

(3) acetic acid

(4) carbonic acid

Correct Answer – (1) lactic acid

Explanation: Like many other things, milk contains bacteria, Milk also naturally contains a kind of sugar known as “lactose.” The bacteria that live in milk get energy from this special sugar and use it to reproduce to make even more bacteria. When the bacteria use the lactose sugars to reproduce, they change it from “lactose sugar” into “lactic acid,” which tastes sour.

Q.4) Which of the following is a natural dye?

(1) Crystal violet

(2) Aniline blue

(3) Alizarin

(4) Phenolphthalein

Correct Answer – (3) Alizarin

Explanation: Alizarin or 1,2- dihydroxyanthraquinone (also known as Mordant Red 11 and Turkey Red is an organic compound with formula C14H8O4 that has been used throughout history as a prominent red dye, principally for dyeing textile fabrics. Historically it was derived from the roots of plants of the madder genus. In 1869, it became the first natural pigment to be duplicated synthetically.

Q.5) The ratio of pure gold in 18 carat gold is

(1) 60%

(2) 75%

(3) 80%

(4) 90%

Correct Answer – (2) 75%

Explanation: There are various grades of gold purity, determined by the ratio of their alloy composition and rated by a karat system. Typical karat purities range from 10 karats to 24 karats (pure gold), with a wide variation of usage from country to country, 18 karat gold consists of 75% gold and 25% alloy metals. 18 karat gold has been found to be the perfect balance between gold purity and strength. Brilliance offers a variety of exquisite 18 karat gold jewelry.

Q.6) _______ is the process in which acids and bases react to form salts and water.

(1) Neutralization

(2) Electrolysis

(3) Distillation

(4) Hydrolysis

Correct Answer – (1) Neutralization

Explanation: Neutralization is a process when acids and bases react to form salt and water.

Q.7) The gas usually causing explosions in coal mines is –

(1) Hydrogen

(2) Carbon monoxide

(3) Air

(4) Methane

Correct Answer – (4) Methane

Explanation: Firedamp is flammable gas found in coal mines. It is the name given to a number of flammable gases, especially methane.

Q.8) Which is the purest form of iron?

(1) Steel

(2) Cast iron

(3) Pig iron

(4) Wrought iron

Correct Answer – (4) Wrought iron

Explanation: Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element (by mass) forming the planet Earth as a whole, forming much of Earth’s outer and inner core. It is the fourth most common element in the Earth’s crust. Wrought iron is the purest form of iron. It contains less than 0.25% carbon.

Q.9) Which of the following metals form an amalgam with other metals?

(1) Lead

(2) Tin

(3) Zinc

(4) Mercury

Correct Answer – (4) Mercury

Explanation: An amalgam is a substance formed by the reaction of mercury with another metal. Almost all metals can form amalgams with mercury, notable exception being iron. Silver-mercury amalgams are important in dentistry, and gold-mercury amalgam is used in the extraction of gold from ore. Dentistry has used alloys of mercury with metals such as silver, copper, indium, tin and zinc. Amalgam is an “excellent and versatile restorative material” and is used in dentistry for a number of reasons.

 Q.10) Petroleum is a mixture of –

(1) elements

(2) hydrocarbons

(3) polymers

(4) salts

Correct Answer – (2) hydrocarbons

Explanation: Petroleum 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. A fossil fuel, it is formed when large quantities of dead organisms, usually zooplankton and algae, are buried underneath sedimentary rock and undergo intense heat and pressure.

 Q.11) The gas used for filling weather balloons is –

(1) helium

(2) hydrogen

(3) air

(4) nitrogen

Correct Answer – (1) helium

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.

Q.12) 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

Correct Answer – (2) liquid in a liquid

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.

Q.13) 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

Correct Answer – (1) 0.1 to 1.5

Explanation: 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.

Q.14) Which of the following gases makes bread or cake rise making them soft and spongy?

(1) CO

(2) H2

(3) CO2

(4) O2

Correct Answer – (3) CO2

Explanation: Breads rise due to the process of fermentation, a chemical process by which molecules such as glucose are broken down an aerobically.

Q.15) Candle is a mixture of –

(1) Paraffin wax and stearic acid

(2) Bees wax and stearic acid

(3) Higher fat acids and stearic acid

(4) Bees wax and paraffin wax

Correct Answer – (1) Paraffin wax and stearic acid

Explanation: The candle can be made of paraffin (a byproduct of petroleum refining), microoystalline wax, stearin (now produced almost exclusively from palm waxes though initially manufactured from animal fats), beeswax (a byproduct of honey collection), gel (a mixture of polymer and mineral oil), some plant waxes (generally palm, carnauba, bayberry, or soybean wax), tallow (rarely used since the introduction of affordable and cheap wax alternatives) or spermaceti (extracted from the head of a Sperm Whale).

Q.16) German silver, an alloy, does not contain the metal –

(1) Nickel

(2) Zinc

(3) Copper

(4) Silver

Correct Answer – (4) Silver

Explanation: Nickel silver 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 (Cupronickel) All modern, commercially important nickel silvers (such as those standardized under ASTM B 122) contain significant amounts of zinc, and are sometimes considered a subset of brass.

Q.17) Oxygen which is vital for life is a product of photosynthesis and comes from –

(1) carbonates from soil

(2) carbon dioxide

 (3) water

(4) oxides of mineral elements

Correct Answer – (3) water

Explanation: The unusually high concentration of oxygen has on Earth is the result of the oxygen cycle. This biogeochemical cycle describes the movement of oxygen within and between its three main reservoirs on Earth: the atmosphere, the biosphere, and the lithosphere. The main driving factor of the oxygen cycle is photosynthesis, which is responsible for modern Earth’s atmosphere. Photosynthesis releases oxygen into the atmosphere, while respiration and decay remove it from the atmosphere.

Q.18) What is the purpose of adding baking soda to dough?

(1) To generate moisture

(2) To give a good flavour

(3) To give good colour

(4) To generate carbon dioxide

Correct Answer – (4) To generate carbon dioxide

Q.19) Gobar gas mainly contains –

(1) Carbon dioxide

(2) Carbon monoxide

(3) Hydrogen sulphide

(4) Methane

Correct Answer – (4) Methane

Explanation: Biogas or Lobar 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.

 Q.20) The chief constituent of vinegar is –

(1) Formic acid

(2) Acetic acid

(3) Salycylic acid

(4) Oxalic acid

Correct Answer – (2) Acetic acid

Explanation: 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.

Q.21) Commercial Vaseline is derived from –

(1) plant gums

(2) coal tar

(3) wool wax

(4) petroleum

Correct Answer – (4) petroleum

Explanation: Vaseline is a brand of petroleum jelly based products owned by Anglo-Dutch company Unilever. While Vaseline can be used as a lubricant, it is also a useful moisture insulator for local skin conditions characterized by tissue dehydration. Vaseline helps protect minor cuts and burns.

Q.22) Colour imparted to the Bunsen flame by strontium salt is –

(1) bluish green

(2) apple-green

(3) brick red

(4) crimson red

Correct Answer – (4) crimson red

Explanation: A flame test is performed by introducing a sample into the blue flame of a bunsen burner and noting any change in the colour of the flame. The tests can be used to detect the presence of some metallic elements in salts. With strontium salt, the colour of Bunsen flame ranges from crimson to red.

Q.23) Name the particle that is most essential to continue the chain reaction during the fission of uranium –

(1) Electron

(2) Proton

(3) Neutron

(4) Positron

Correct Answer – (3) Neutron

Explanation: Nuclear fission is either a nuclear reaction or a radioactive decay process in which the nucleus of an atom splits into smaller parts (lighter nuclei), often producing free neutrons and photons (in the form of gamma rays), and releasing a very large amount of energy, even by the energetic standards of radioactive decay. Fission as encountered in the modern world is usually a deliberately produced manmade nuclear reaction induced by a neutron.

 Q.24) Which one amongst the following is not a Green House gas?

(1) Nitrogen

(2) Carbon dioxide

(3) Carbon Monoxide

(4) Chloro fluoro carbons

Correct Answer – (1) Nitrogen

Explanation: A greenhouse has (sometimes abbreviated GHG) is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. The primary greenhouse gases in the Earth’s atmosphere are water vapour, carbon dioxide, methane, nitrous oxide, and ozone.

Q.25) The element used in the manufacture of safety matches is –

(1) Phosphorous

(2) Magnesium

(3) Silicon

(4) Sulphur

Correct Answer – (1) Phosphorous

Explanation: One end of a match is coated with a material that can be ignited by frictional heat generated by striking the match against a suitable surface. The coated end of a match, known as the match “head,” contains either phosphorus or phosphorus sesquisulfide as the active ingredient and gelatin as a binder.

Q.26) The main source of Naphthalene is –

(1) Charcoal

(2) Camphor

(3) Coal-tar

(4) Diesel

Correct Answer – (3) Coal-tar

Explanation: The main source of Naphthalene is coal-tar. Naphthalene is derived from a kind of naphtha which is a broad term encompassing any volatile, namable liquid hydrocarbon mixture, including coaltar.

Q.27) The material used in solar cells contains

(1) Tin

(2) Silicon

(3) Caesium

(4) Thallium

Correct Answer – (2) Silicon

Explanation: A solar cell (also called a photovoltaic cell) is an electrical device that converts the energy of light directly into electricity by the photovoltaic effect. Materials presently used for photovoltaic solar cells include mono-crystalline silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, and copper iridium selenide/sulfide.

Q.28) Quartz is a crystalline form of –

(1) Alumina

(2) Glass

(3) Silica

(4) Limestone

Correct Answer – (3) Silica

Explanation: Quartz 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. Tridymite and cristobalite are hightemperature polymorphs of SiO2 that occur in high-silica volcanic rocks. Coesite is a denser polymorph of quartz found in some meteorite impact sites and in metamorphic rocks.

Q.29) In vulcanisation process, rubber can be hardened by adding –

(1) Nitrogen

(2) Silicon

(3) Sulphur

(4) Alcohol

Correct Answer – (3) Sulphur

Explanation: In order to give more strength and more elasticity, natural rubber is heated with sulphur or sulphur compounds at 150°C temperature. Vulcanized rubber has good tensile strength.

Q.30) Urea is a –

(1) Sodium fertilizer

(2) Phosphatic fertilizer

(3) Nitrogenous fertilizer

(4) Potassium fertilizer

Correct Answer – (3) Nitrogenous fertilizer

Explanation: More than 90% of world production of urea is destined for use as a nitrogen-release fertilizer. Urea has the highest nitrogen content of all solid nitrogenous fertilizers in common use.

Q.31) During inter conversion of energy from one form to other forms, total energy at any time remains–

(1) constant

(2) zero

(3) increasing

(4) decreasing

Correct Answer – (1) constant

Explanation: During interconversion of energy from one form to other forms, total energy at any time remains constant.

Q.32) Which of the following is a physical change?

(1) oxidation

(2) reduction

(3) sublimation

(4) decomposition

Correct Answer – (3) sublimation

Explanation: Sublimation is a type of phase transition, or a change in a state of matter, just like melting, freezing, and evaporation.

Q.33) Sea weeds are important source of –

(1) iron

(2) chlorine

(3) bromine

(4) iodine

Correct Answer – (4) iodine

Explanation: Seaweed is a source of iodine, necessaly 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-mempausal women.

Q.34) Which gas is used to manufacture vanaspati from vegetable oil is –

(1) carbon dioxide

(2) nitrogen

(3) oxygen

(4) hydrogen

Correct Answer – (4) hydrogen

Explanation: Hydrogen is used to manufacture vanaspati from vegetable oil.

Q.35) The pH of a neutral solution is –

(1) 0-7

(2) 7

(3) 7-14

(4) None of the above

Correct Answer – (2) 7

Explanation: The pH of a neutral solution is 7. Values less than 7 on the pH scale represent an acidic solution. As the pH value increases from 7 to 14, the solution turns more basic.

Q.36) The nucleus of an atom consists of –

(1) electrons and neutrons

(2) electrons and protons

(3) protons and neutrons

(4) All of the above

Correct Answer – (3) protons and neutrons

Explanation: The atomic nucleus consists of nucleons—protons and neutrons. Protons and neutrons are made of quarks and held together by the strong force generated by gluon exchange between quarks.

Q.37) Detergents are –

(1) Sodium salts of fatty acids

(2) Sodium salts of sulphonic acids

(3) Sodium salt of benzoic acid

(4) None of the above

Correct Answer – (2) Sodium salts of sulphonic acids

Explanation: A detergent is a surfactant or a mixture of surfactants with “cleaning properties in dilute solutiops.” These substances are usually alkylbenzenesulfonates, a family of compounds that are similar to soap but are more soluble in hard water, because the polar sulfonate (of detergents) is less likely than the polar carboxyl (of soap) to bind to calcium and other ions found in hard water. In most household contexts, the term detergent by itself refers specifically to laundry detergent or dish detergent, as opposed to hand soap or other types of cleaning agents.

 Q.38) The noble gas used in radiotherapy is

(1) neon

(2) argon

(3) radon

(4) xenon

Correct Answer – (3) radon

Explanation: An early-20th-century form of quackery was the treatment of maladies in a radiotorium. It was a small, sealed room for patients to be exposed to radon for its “medicinal effects”. The carcinogenic nature of radon due to its ionizing radiation became apparent later on. Radon’s molecule-damaging radioactivity has been used to kill cancerous cells. It does not, however, increase the health of healthy cells. In fact, the ionizing radiation causes the formation of free radicals, which results in genetic and other cell damage, resulting in increased rates of illness, including cancer.

Q.39) Ethanol containing 5% water is known as –

(1) rectified spirit

(2) denatured spirit

(3) methylated alcohol

(4) power alcohol

Correct Answer – (1) rectified spirit

Explanation: A rectified spirit, rectified alcohol, or neutral spirit is highly concentrated ethanol which has been purified by means of repeated distillation, a process that is called rectification. It typically contains 95% alcohol by volume (ABV). Rectified spirits are used in mixed drinks, in the production of liqueurs, for medicinal purposes, and as a household solvent.

Q.40) The important ore of aluminium is –

(1) bauxite

(2) cryolite

(3) fluorspar

(4) haematite

Correct Answer – (1) 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 TiO2. Bauxite was named after the village Les Baux in southern France, where it was first recognized as containing aluminium and named by the French geologist Pierre Berthier in 1821.

Q.41) Which of the following is not present in German-silver?

(1) Copper

(2) Nickel

(3) Silver

(4) Zinc

Correct Answer – (3) Silver

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.

Q.42) The major harmful gas emitted by automobile vehicles which causes air pollution is –

(1) Carbon Monoxide

(2) Methane

(3) Carbon dioxide

(4) Ozone gas

Correct Answer – (1) Carbon Monoxide

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.

Q.43) Who discovered the atom bomb?

(1) Madam Curie

(2) Pierre Curie

(3) Otto Hahn

(4) Albert Einstein

Correct Answer – (3) Otto Hahn

Explanation: Otto Hahn, (8 March, 1879 – 28 July, 1968) was a German chemist and Nobel laureate, a pioneer in the fields of radioactivity and radiochemistry. 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.

Q.44) The major component of honey is –

(1) glucose

(2) sucrose

(3) maltose

(4) fructose

Correct Answer – (4) fructose

Explanation: Honey is a supersaturated sugar solution with approximately 17.1 percent water. Fructose is the predominant sugar at 38.5 percent, followed by glucose at 31 percent.

Q.45) A body moving in a circular path with a constant speed has a –

(1) constant velocity

(2) constant acceleration

(3) constant kinetic energy

(4) constant displacement

Correct Answer – (3) constant kinetic energy

Explanation: In circular motion, the magnitude of the velocity of the body is constant but the direction is constantly changing.

Q46) ______ is a multibranched polysaccharide of glucose that serves as a form of energy storage in animals and fungi.

(1) Cellulose

(2) Glycogen

(3) Pectin

(4) Chitin

Correct Answer – (2) Glycogen

Explanation: Glycogen is a multi branched polysaccharide of glucose that serves as a form of emery storage in humans animals, and fungi.

Q.47) Potassium Permanganate is used for purifying drinking water, because –

(1) it dissolves the impurities of water

(2) It is a sterilizing agent

(3) It is an oxidising agent

(4) It is a reducing agent

Correct Answer – (3) It is an oxidising agent

Explanation: Potassium permanganate is a point-of-entry treatment method that oxidizes dissolved iron, manganese, and hydrogen sulfide into solid particles that are filtered out of the water.

Q.48) Diamond is harder than graphite because of –

(1) difference in layers of atoms

(2) tetrahedral structure of diamond

(3) difference of crystalline structures

(4) None of these

Correct Answer – (1) difference in layers of atoms

Explanation: Diamond is harder than graphite because diamond has a more complex structure. Diamond’s structure is like many pentagons connected together, each pentagon sharing a side with another pentagon or each pentagon sharing a point with another pentagon. All the points are linked together in some way. Graphite’s structure is very loose, with its bonds forming layers.

Q.49) Gobar gas contains mainly –

(1) methane

(2) ethylene

(3) propylene

(4) acetylene

Correct Answer – (1) methane

Explanation: Bio gas is a clean unpolluted and cheap source of energy in rural areas. It consists of 55-70% methane which is inflammable. Bio gas is produced from cattle dung in a bio gas plant commonly known as gobar gas plant through a process called digestion. It helps in reducing the deforestation as it arrests for cutting of trees for firewood. It also helps in maintaining ecological balance, in rural sanitation and it needs Lower capital cost and almost cost free maintenance.

Q.50) What is the most commonly used substance in fluorescent tubes?

(1) Sodium oxide and argon

(2) Sodium vapour and neon

(3) Mercury vapour and argon

(4) Mercury oxide and neon

Correct Answer – (3) Mercury vapour and argon

Explanation: A fluorescent lamp or fluorescent tube is a gas-discharge lamp that uses electricity to excite mercury vapour. it contains mercury vapour and argon. The excited mercury atoms produce short-wave ultraviolet light that then causes a phosphor to fluoresce, producing visible light. A fluorescent lamp converts electrical power into useful light more efficiently than an incandescent lamp.

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