Top 100 Chemistry MCQ Questions with Answers
The 100 most important Chemistry questions — pulled from our full bank of 200 Chemistry questions, ranked by how frequently they're asked in real exams. Answers and explanations are shown directly below each question.
1.The pH of pure water at 25 °C is:
easy- A.0
- B.10
- C.14
- D.7 Correct Answer
Explanation: Pure water is neutral, with pH 7. Values below 7 are acidic and above 7 are basic.
Practice more on this topic →2.The sour taste of lemon is due to the presence of:
easy- A.acetic acid
- B.lactic acid
- C.citric acid Correct Answer
- D.oxalic acid
Explanation: Citrus fruits such as lemon and orange contain citric acid.
Practice more on this topic →3.Vinegar is a dilute solution of:
easy- A.formic acid
- B.citric acid
- C.acetic acid Correct Answer
- D.tartaric acid
Explanation: Vinegar contains about 5 to 8 per cent acetic acid in water.
Practice more on this topic →4.Blue litmus paper turns red in a solution that is:
easy- A.basic
- B.acidic Correct Answer
- C.neutral
- D.colloidal
Explanation: Acids turn blue litmus red; bases turn red litmus blue.
Practice more on this topic →5.Sodium hydroxide (NaOH) is commonly known as:
easy- A.baking soda
- B.caustic soda Correct Answer
- C.washing soda
- D.bleaching powder
Explanation: NaOH is a strong base called caustic soda; it is used in making soap.
Practice more on this topic →6.The chemical name of baking soda is:
easy- A.sodium carbonate
- B.sodium hydrogencarbonate Correct Answer
- C.sodium chloride
- D.calcium carbonate
Explanation: Baking soda is NaHCO3. Washing soda is Na2CO3·10H2O.
Practice more on this topic →7.Milk of magnesia, used as an antacid, is chemically:
medium- A.magnesium chloride
- B.sodium hydroxide
- C.magnesium hydroxide Correct Answer
- D.aluminium oxide
Explanation: Mg(OH)2 is a mild base that neutralises excess stomach acid.
Practice more on this topic →8.Bleaching powder is produced by passing chlorine gas over:
medium- A.quicklime
- B.limestone
- C.caustic soda
- D.dry slaked lime Correct Answer
Explanation: Ca(OH)2 + Cl2 gives CaOCl2, which is bleaching powder.
Practice more on this topic →9.Washing soda crystals contain how many molecules of water of crystallisation?
medium- A.10 Correct Answer
- B.5
- C.7
- D.2
Explanation: Washing soda is Na2CO3·10H2O.
Practice more on this topic →10.Plaster of Paris is prepared by heating:
medium- A.gypsum Correct Answer
- B.limestone
- C.quicklime
- D.chalk
Explanation: Heating gypsum (CaSO4·2H2O) at about 373 K gives Plaster of Paris (CaSO4·½H2O).
Practice more on this topic →11.The pH of normal human blood is about:
medium- A.6.4
- B.8.4
- C.5.4
- D.7.4 Correct Answer
Explanation: Blood is slightly basic, with a pH of about 7.35 to 7.45.
Practice more on this topic →12.Rain water is called acid rain when its pH falls below about:
medium- A.7.0
- B.5.6 Correct Answer
- C.6.5
- D.4.0
Explanation: Clean rain is slightly acidic (pH about 5.6) because of dissolved carbon dioxide; below that it is acid rain.
Practice more on this topic →13.Which of the following is a strong acid?
medium- A.acetic acid
- B.carbonic acid
- C.citric acid
- D.hydrochloric acid Correct Answer
Explanation: HCl ionises almost completely in water, so it is a strong acid. The others are weak acids.
Practice more on this topic →14.The reaction of an acid with a base to form a salt and water is called:
medium- A.hydrolysis
- B.esterification
- C.neutralisation Correct Answer
- D.oxidation
Explanation: Acid + base gives salt + water, for example HCl + NaOH gives NaCl + H2O.
Practice more on this topic →15.The chlor-alkali process uses which solution as its raw material?
medium- A.lime water
- B.dilute sulphuric acid
- C.brine (sodium chloride solution) Correct Answer
- D.bleaching powder solution
Explanation: Electrolysis of brine gives sodium hydroxide, chlorine and hydrogen.
Practice more on this topic →16.The pH of gastric juice in the human stomach is about:
medium- A.5.0 to 6.0
- B.7.0 to 8.0
- C.9.0 to 10.0
- D.1.5 to 2.0 Correct Answer
Explanation: Stomach acid, mainly hydrochloric acid, is strongly acidic with a pH of about 1.5 to 2.
Practice more on this topic →17.Aqua regia, which can dissolve gold and platinum, is a mixture of concentrated HCl and HNO3 in the ratio:
hard- A.1 : 3
- B.3 : 1 Correct Answer
- C.1 : 1
- D.2 : 1
Explanation: Aqua regia is 3 parts concentrated hydrochloric acid to 1 part concentrated nitric acid.
Practice more on this topic →18.The pH of a 0.001 M solution of hydrochloric acid is:
hard- A.3 Correct Answer
- B.1
- C.4
- D.11
Explanation: HCl is fully ionised, so [H+] = 10⁻³ M and pH = -log(10⁻³) = 3.
Practice more on this topic →19.Which scientists independently proposed in 1923 that an acid is a proton donor and a base is a proton acceptor?
hard- A.Brønsted and Lowry Correct Answer
- B.Arrhenius and Faraday
- C.Lewis and Dalton
- D.Bohr and Rutherford
Explanation: The Brønsted-Lowry theory defines acids as proton donors and bases as proton acceptors. Arrhenius defined them by ions in water; Lewis by electron pairs.
Practice more on this topic →20.Which compound, known as "hypo", is used as a fixer in photography?
hard- A.sodium thiosulphate Correct Answer
- B.sodium chloride
- C.potassium nitrate
- D.copper sulphate
Explanation: Sodium thiosulphate (hypo) dissolves unexposed silver halide from film and paper, fixing the image.
Practice more on this topic →21.The nucleus of the atom was discovered by:
easy- A.Ernest Rutherford Correct Answer
- B.J. J. Thomson
- C.James Chadwick
- D.Niels Bohr
Explanation: Rutherford's gold foil experiment revealed a small dense nucleus.
Practice more on this topic →22.The neutron was discovered by:
easy- A.Ernest Rutherford
- B.Robert Millikan
- C.James Chadwick Correct Answer
- D.Henry Moseley
Explanation: Chadwick found it in 1932.
Practice more on this topic →23.The charge on a neutron is:
easy- A.positive
- B.negative
- C.variable
- D.zero Correct Answer
Explanation: Neutrons are electrically neutral.
Practice more on this topic →24.The atomic number of an element is equal to the number of:
easy- A.neutrons
- B.nucleons
- C.protons Correct Answer
- D.molecules
Explanation: It defines the identity of an element.
Practice more on this topic →25.The mass number of an atom is the sum of its:
easy- A.protons and neutrons Correct Answer
- B.protons and electrons
- C.electrons and neutrons
- D.electrons only
Explanation: Protons and neutrons are together called nucleons.
Practice more on this topic →26.The plum pudding model of the atom was proposed by:
easy- A.Rutherford
- B.Bohr
- C.J. J. Thomson Correct Answer
- D.Dalton
Explanation: Electrons were pictured embedded in a positive sphere.
Practice more on this topic →27.Isotopes are atoms of the same element with the same:
medium- A.mass number but different atomic numbers
- B.neutrons only
- C.atomic number but different mass numbers Correct Answer
- D.electrons but different protons
Explanation: They differ in the number of neutrons.
Practice more on this topic →28.Isobars are atoms with the same:
medium- A.atomic number but different mass numbers
- B.mass number but different atomic numbers Correct Answer
- C.number of neutrons
- D.chemical properties
Explanation: Argon-40 and calcium-40 are examples.
Practice more on this topic →29.Isotones are atoms with the same number of:
medium- A.protons
- B.electrons
- C.neutrons Correct Answer
- D.nucleons
Explanation: They have different atomic numbers.
Practice more on this topic →30.Bohr's model of the atom states that electrons revolve in:
medium- A.random paths
- B.the nucleus
- C.straight lines
- D.fixed circular orbits with definite energies Correct Answer
Explanation: Energy is emitted or absorbed only when electrons jump between orbits.
Practice more on this topic →31.The maximum number of electrons in the K shell is:
medium- A.2 Correct Answer
- B.8
- C.18
- D.32
Explanation: The maximum in a shell is 2n², and n = 1 here.
Practice more on this topic →32.The maximum number of electrons in the L shell is:
medium- A.2
- B.8 Correct Answer
- C.18
- D.32
Explanation: 2n² with n = 2 gives 8.
Practice more on this topic →33.Which isotope of hydrogen has no neutron?
medium- A.deuterium
- B.protium Correct Answer
- C.tritium
- D.none of them
Explanation: Protium is the only common hydrogen isotope with just one proton and no neutron.
Practice more on this topic →34.Which isotope is used for radiocarbon dating?
medium- A.carbon-12
- B.uranium-235
- C.iodine-131
- D.carbon-14 Correct Answer
Explanation: Its radioactive decay gives the age of organic remains.
Practice more on this topic →35.The number of valence electrons in a sodium atom is:
medium- A.2
- B.1 Correct Answer
- C.8
- D.11
Explanation: Its configuration is 2, 8, 1.
Practice more on this topic →36.The charge on a proton is:
medium- A.negative
- B.zero
- C.double that of an electron
- D.positive and equal in magnitude to that of an electron Correct Answer
Explanation: The two charges make a neutral atom.
Practice more on this topic →37.Rutherford's alpha-particle scattering experiment used a thin foil of:
hard- A.gold Correct Answer
- B.silver
- C.copper
- D.iron
Explanation: Most particles passed straight through, a few were deflected sharply.
Practice more on this topic →38.Heisenberg's uncertainty principle states that it is impossible to know simultaneously and exactly an electron's:
hard- A.charge and mass
- B.spin and colour
- C.energy and shape
- D.position and momentum Correct Answer
Explanation: It limits how precisely both can be defined.
Practice more on this topic →39.Pauli's exclusion principle states that no two electrons in an atom can have:
hard- A.the same charge
- B.the same set of four quantum numbers Correct Answer
- C.the same mass
- D.the same shell
Explanation: So an orbital holds at most two electrons of opposite spin.
Practice more on this topic →40.The fractional atomic mass of chlorine (35.5) arises because of its:
hard- A.isotopes chlorine-35 and chlorine-37 Correct Answer
- B.isobars
- C.allotropes
- D.impurities
Explanation: It is the weighted average of the isotopes by natural abundance.
Practice more on this topic →41.Sodium chloride is held together by:
easy- A.covalent bonds
- B.ionic bonds Correct Answer
- C.metallic bonds
- D.hydrogen bonds
Explanation: Sodium transfers an electron to chlorine.
Practice more on this topic →42.A covalent bond is formed by:
easy- A.sharing of electrons Correct Answer
- B.transfer of protons
- C.transfer of neutrons
- D.attraction between nuclei
Explanation: Atoms share pairs of electrons to complete their outer shells.
Practice more on this topic →43.Rusting of iron is an example of:
easy- A.reduction only
- B.oxidation Correct Answer
- C.sublimation
- D.neutralisation
Explanation: Iron reacts with oxygen and moisture.
Practice more on this topic →44.Burning of magnesium ribbon in air is a:
easy- A.combination reaction Correct Answer
- B.decomposition reaction
- C.displacement reaction
- D.neutralisation reaction
Explanation: Magnesium combines with oxygen to form magnesium oxide.
Practice more on this topic →45.The chemical formula of water is:
easy- A.H2O2
- B.HO
- C.H2O Correct Answer
- D.H3O
Explanation: Two hydrogen atoms bond to one oxygen atom.
Practice more on this topic →46.Photosynthesis is:
easy- A.an endothermic reaction Correct Answer
- B.an exothermic reaction
- C.a neutralisation reaction
- D.a nuclear reaction
Explanation: It absorbs light energy.
Practice more on this topic →47.Ionic compounds generally have:
medium- A.low melting points
- B.no charge
- C.gas state at room temperature
- D.high melting and boiling points Correct Answer
Explanation: Strong electrostatic forces hold the ions together.
Practice more on this topic →48.In an oxygen molecule (O2) the atoms are joined by a:
medium- A.single bond
- B.double bond Correct Answer
- C.triple bond
- D.ionic bond
Explanation: Each oxygen atom shares two electrons.
Practice more on this topic →49.In a nitrogen molecule (N2) the atoms are joined by a:
medium- A.single bond
- B.double bond
- C.triple bond Correct Answer
- D.ionic bond
Explanation: The triple bond makes nitrogen very unreactive.
Practice more on this topic →50.Respiration in living cells is:
medium- A.an endothermic reaction
- B.a displacement reaction
- C.a precipitation reaction
- D.an exothermic reaction Correct Answer
Explanation: Glucose is oxidised and releases energy.
Practice more on this topic →51.Heating calcium carbonate to give calcium oxide and carbon dioxide is a:
medium- A.combination reaction
- B.displacement reaction
- C.decomposition reaction Correct Answer
- D.neutralisation reaction
Explanation: One compound breaks into simpler substances.
Practice more on this topic →52.Iron placed in copper sulphate solution turns the solution green and deposits copper. This is a:
medium- A.decomposition reaction
- B.combination reaction
- C.displacement reaction Correct Answer
- D.double decomposition reaction
Explanation: The more reactive iron displaces copper.
Practice more on this topic →53.A catalyst:
medium- A.is used up completely
- B.slows every reaction
- C.changes the products always
- D.speeds up a reaction without being consumed Correct Answer
Explanation: It provides an alternative path with lower activation energy.
Practice more on this topic →54.In terms of electrons, oxidation is:
medium- A.gain of electrons
- B.sharing of protons
- C.loss of electrons Correct Answer
- D.gain of neutrons
Explanation: Remember OIL RIG: oxidation is loss, reduction is gain.
Practice more on this topic →55.Mixing silver nitrate and sodium chloride solutions gives a white:
medium- A.gas of chlorine
- B.solution of silver
- C.flame
- D.precipitate of silver chloride Correct Answer
Explanation: Silver chloride is insoluble in water.
Practice more on this topic →56.Which of the following has a covalent bond?
medium- A.hydrogen chloride (HCl) Correct Answer
- B.sodium chloride (NaCl)
- C.potassium chloride (KCl)
- D.magnesium oxide (MgO)
Explanation: HCl shares a pair of electrons between H and Cl, while the others are ionic.
Practice more on this topic →57.The unusually high boiling point of water is due to:
hard- A.ionic bonding
- B.hydrogen bonding Correct Answer
- C.metallic bonding
- D.nuclear forces
Explanation: Water molecules attract each other through O-H···O bonds.
Practice more on this topic →58.In a coordinate (dative) bond, the shared pair of electrons is:
hard- A.donated equally by both atoms
- B.donated by one atom only Correct Answer
- C.absent
- D.taken from the nucleus
Explanation: Ammonium ion formation is an example.
Practice more on this topic →59.In the Haber process for ammonia, the catalyst used is:
hard- A.iron Correct Answer
- B.platinum
- C.nickel
- D.vanadium pentoxide
Explanation: Nitrogen and hydrogen combine at high pressure over finely divided iron.
Practice more on this topic →60.Le Chatelier's principle predicts how a system at equilibrium responds to:
hard- A.a change in its colour only
- B.the passage of time alone
- C.the shape of the container
- D.a change in conditions such as concentration, pressure or temperature Correct Answer
Explanation: The system shifts to oppose the imposed change.
Practice more on this topic →61.The chemical name of caustic soda is:
easy- A.sodium hydroxide Correct Answer
- B.sodium carbonate
- C.sodium bicarbonate
- D.potassium hydroxide
Explanation: Sodium hydroxide, NaOH, is a strong base used in making soap.
Practice more on this topic →62.Penicillin, the first antibiotic, was discovered by:
easy- A.Louis Pasteur
- B.Alexander Fleming Correct Answer
- C.Robert Koch
- D.Edward Jenner
Explanation: Fleming observed it in 1928.
Practice more on this topic →63.The chemical formula of common salt is:
easy- A.KCl
- B.NaOH
- C.NaCl Correct Answer
- D.Na2CO3
Explanation: It is sodium chloride.
Practice more on this topic →64.Aspirin is commonly used as a:
easy- A.antibiotic
- B.pain reliever and fever reducer Correct Answer
- C.antacid
- D.sleeping drug only
Explanation: It is an analgesic and antipyretic.
Practice more on this topic →65.The chemical formula of table sugar (sucrose) is:
easy- A.C12H22O11 Correct Answer
- B.C6H12O6
- C.C2H5OH
- D.CH3COOH
Explanation: Glucose is C6H12O6.
Practice more on this topic →66.Washing soda has the chemical name:
easy- A.sodium bicarbonate
- B.sodium sulphate
- C.sodium nitrate
- D.sodium carbonate Correct Answer
Explanation: Its hydrated form is Na2CO3·10H2O.
Practice more on this topic →67.Antacids are used to:
medium- A.kill bacteria
- B.reduce fever
- C.induce sleep
- D.neutralise excess acid in the stomach Correct Answer
Explanation: Magnesium hydroxide is a common antacid.
Practice more on this topic →68.A common food preservative is:
medium- A.sodium hydroxide
- B.sodium sulphate
- C.sodium benzoate Correct Answer
- D.saccharin
Explanation: It prevents growth of microbes in pickles and drinks.
Practice more on this topic →69.Detergents are preferred to soaps for washing in hard water because they:
medium- A.are always cheaper
- B.contain no chemicals
- C.dissolve only in oil
- D.do not form scum with calcium and magnesium ions Correct Answer
Explanation: Soap forms insoluble scum in hard water.
Practice more on this topic →70.Vitamin C is chemically known as:
medium- A.ascorbic acid Correct Answer
- B.citric acid
- C.lactic acid
- D.folic acid
Explanation: Its deficiency causes scurvy.
Practice more on this topic →71.Chlorine is added to drinking water to:
medium- A.kill germs Correct Answer
- B.add taste
- C.make it harder
- D.increase its colour
Explanation: Bleaching powder is also used for this purpose.
Practice more on this topic →72.An artificial sweetener is:
medium- A.sucrose
- B.fructose
- C.saccharin Correct Answer
- D.glucose
Explanation: It is hundreds of times sweeter than sugar.
Practice more on this topic →73.Paracetamol is a:
medium- A.antibiotic
- B.antacid
- C.vitamin
- D.pain reliever and fever reducer Correct Answer
Explanation: It is an analgesic and antipyretic.
Practice more on this topic →74.Plaster of Paris has the formula:
medium- A.CaSO4·2H2O
- B.CaSO4·½H2O Correct Answer
- C.CaCO3
- D.CaO
Explanation: Plaster of Paris, CaSO4·½H2O, is made by heating gypsum, which holds more water of crystallisation.
Practice more on this topic →75.The difference between antiseptics and disinfectants is that antiseptics are applied to:
medium- A.floors and drains only
- B.living tissue Correct Answer
- C.non-living surfaces only
- D.food only
Explanation: Disinfectants are used on non-living objects.
Practice more on this topic →76.Bleaching powder is chemically:
medium- A.calcium carbonate
- B.sodium hypochlorite only
- C.calcium oxychloride (calcium hypochlorite chloride) Correct Answer
- D.calcium sulphate
Explanation: It is made by passing chlorine over slaked lime.
Practice more on this topic →77.Tranquilisers such as diazepam are used to:
hard- A.kill bacteria
- B.reduce stomach acid
- C.reduce anxiety and tension Correct Answer
- D.lower fever
Explanation: They act on the central nervous system.
Practice more on this topic →78.Gypsum is added during cement manufacture to:
hard- A.increase the colour
- B.control the setting time Correct Answer
- C.make it magnetic
- D.reduce the weight
Explanation: Without it cement would set too quickly.
Practice more on this topic →79.Antipyretics are drugs that:
hard- A.reduce body temperature in fever Correct Answer
- B.kill all bacteria
- C.induce vomiting
- D.increase appetite
Explanation: Paracetamol is an example.
Practice more on this topic →80.The raw materials of ordinary glass include:
hard- A.clay and gypsum only
- B.iron ore and coke
- C.bauxite and cryolite
- D.sand, soda ash and limestone Correct Answer
Explanation: Silica from sand is the main component.
Practice more on this topic →81.The ozone layer protects life on Earth by absorbing:
easy- A.visible light
- B.radio waves
- C.harmful ultraviolet radiation Correct Answer
- D.sound waves
Explanation: It lies in the stratosphere.
Practice more on this topic →82.Which gas is the main contributor to the greenhouse effect among the following?
easy- A.argon
- B.neon
- C.helium
- D.carbon dioxide Correct Answer
Explanation: It traps outgoing heat radiation.
Practice more on this topic →83.Acid rain is mainly caused by oxides of:
easy- A.carbon only
- B.hydrogen
- C.sulphur and nitrogen Correct Answer
- D.helium
Explanation: They form sulphuric and nitric acids in the air.
Practice more on this topic →84.Which chemicals are mainly responsible for ozone layer depletion?
easy- A.carbon dioxide
- B.chlorofluorocarbons (CFCs) Correct Answer
- C.methane
- D.ammonia
Explanation: Chlorine atoms from CFCs destroy ozone molecules.
Practice more on this topic →85.Which poisonous gas from vehicle exhaust binds to haemoglobin?
easy- A.oxygen
- B.nitrogen
- C.carbon monoxide Correct Answer
- D.argon
Explanation: It reduces the oxygen-carrying capacity of blood.
Practice more on this topic →86.Plastic waste is a pollution problem mainly because it is:
easy- A.non-biodegradable Correct Answer
- B.soluble in water
- C.a fertiliser
- D.a gas
Explanation: It persists in the environment for very long.
Practice more on this topic →87.The ozone hole is most prominent over:
medium- A.the Sahara
- B.the Amazon
- C.Antarctica Correct Answer
- D.India
Explanation: Polar stratospheric clouds help the destruction every spring.
Practice more on this topic →88.The Montreal Protocol (1987) deals with:
medium- A.reducing carbon dioxide only
- B.protecting wetlands
- C.trade in wildlife
- D.phasing out ozone-depleting substances Correct Answer
Explanation: It is regarded as one of the most successful environmental treaties.
Practice more on this topic →89.Minamata disease is caused by poisoning from:
medium- A.lead
- B.cadmium
- C.mercury Correct Answer
- D.arsenic
Explanation: It was first noticed in Japan in fish-eating communities.
Practice more on this topic →90.The Bhopal gas tragedy of 1984 was caused by the leak of:
medium- A.methyl isocyanate Correct Answer
- B.carbon monoxide
- C.chlorine
- D.ammonia
Explanation: It leaked from a pesticide plant.
Practice more on this topic →91.BOD stands for:
medium- A.biological ozone depletion
- B.biochemical oxygen demand Correct Answer
- C.basic organic density
- D.bulk oxygen deficit
Explanation: A higher BOD indicates more organic pollution in water.
Practice more on this topic →92.Excess nutrients such as nitrates and phosphates in a lake cause:
medium- A.desertification
- B.acid rain
- C.ozone depletion
- D.eutrophication Correct Answer
Explanation: Algal blooms then deplete oxygen in the water.
Practice more on this topic →93.Photochemical smog is formed from:
medium- A.nitrogen oxides and hydrocarbons in sunlight Correct Answer
- B.carbon dioxide and nitrogen
- C.oxygen and argon
- D.water vapour and helium
Explanation: It contains ozone and peroxyacetyl nitrate at ground level.
Practice more on this topic →94.Which greenhouse gas is released in large amounts from paddy fields and cattle?
medium- A.argon
- B.neon
- C.oxygen
- D.methane Correct Answer
Explanation: Anaerobic decay of organic matter produces it.
Practice more on this topic →95.The thickness of the ozone layer is measured in:
medium- A.decibels
- B.pascals
- C.lux
- D.Dobson units Correct Answer
Explanation: About 300 Dobson units is typical globally.
Practice more on this topic →96.PM2.5 refers to airborne particles with a diameter of:
medium- A.2.5 micrometres or less Correct Answer
- B.2.5 millimetres
- C.25 micrometres
- D.2.5 centimetres
Explanation: Such fine particles enter deep into the lungs.
Practice more on this topic →97.The Kyoto Protocol (1997) seeks to reduce emissions of:
hard- A.greenhouse gases Correct Answer
- B.only radioactive waste
- C.only noise
- D.only plastics
Explanation: It set targets for developed countries.
Practice more on this topic →98.Rainwater is considered acid rain when its pH falls below about:
hard- A.7.0
- B.5.6 Correct Answer
- C.8.5
- D.10.0
Explanation: Normal rain is slightly acidic because of dissolved carbon dioxide.
Practice more on this topic →99.Itai-itai disease is caused by poisoning from:
hard- A.mercury
- B.cadmium Correct Answer
- C.iron
- D.sodium
Explanation: It was linked to cadmium in rice grown with polluted water.
Practice more on this topic →100.Ozone is formed in the stratosphere from:
hard- A.nitrogen under heat
- B.oxygen under ultraviolet radiation Correct Answer
- C.carbon dioxide under pressure
- D.water vapour under cold
Explanation: UV splits O2 and the atoms combine with O2 to give O3.
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