NDA Part B General Knowledge - Chemistry Practice Test 100 MCQs

NDA Part B General Knowledge - Chemistry Practice Test

Targeted 100 MCQ Practice Module focusing on: Structure of Atom, Acids, Bases & Salts; Metals & Non-metals, Elements, Compounds & Mixtures; Carbon & its Compounds, Oxidation & Reduction; Air, Water, Fertilizers, Soap, Glass & Everyday Chemistry.

Select your answers and click Submit Assessment Answers at the bottom to calculate your total score and review explanations.

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SECTION I: Structure of Atom, Acids, Bases & Salts [Questions 1 to 25]

1. Who discovered the electron in 1897 through cathode ray tube experiments?

Ernest Rutherford J.J. Thomson James Chadwick Niels Bohr

Explanation: J.J. Thomson's cathode ray experiments revealed negatively charged particles, later named electrons. He also proposed the plum-pudding model of the atom.

2. The neutron was discovered in 1932 by:

E. Goldstein R.A. Millikan Henry Moseley James Chadwick

Explanation: Chadwick bombarded beryllium with alpha particles and detected neutral particles of mass nearly equal to the proton. Goldstein discovered the proton (canal rays).

3. Rutherford's alpha-particle scattering experiment led to the discovery of:

the electron the atomic nucleus the neutron discrete energy levels

Explanation: Most alpha particles passed straight through gold foil, a few deflected sharply and very few rebounded, showing a small, dense, positively charged nucleus.

4. The atomic number of an element is equal to the number of:

neutrons in its nucleus nucleons in its nucleus protons in its nucleus valence electrons

Explanation: Atomic number (Z) is the number of protons; it defines the identity of the element.

5. An atom has 17 protons and 18 neutrons. Its mass number is:

17 18 35 36

Explanation: Mass number = protons + neutrons = 17 + 18 = 35 (this is chlorine-35).

6. How many neutrons are present in a tritium (³H) atom?

0 1 3 2

Explanation: Tritium has mass number 3 and atomic number 1, so neutrons = 3 − 1 = 2.

7. Which pair represents isobars?

¹²C and ¹⁴C ³⁵Cl and ³⁷Cl ⁴⁰Ar and ⁴⁰Ca ¹H and ²H

Explanation: Isobars have the same mass number but different atomic numbers. Argon-40 (Z = 18) and calcium-40 (Z = 20) fit this. The other pairs are isotopes.

8. Which pair represents isotones (same number of neutrons)?

¹²C and ¹³C ¹⁶O and ¹⁸O ¹⁴C and ¹⁵N ³⁵Cl and ³⁷Cl

Explanation: ¹⁴C has 14 − 6 = 8 neutrons and ¹⁵N has 15 − 7 = 8 neutrons, so they are isotones.

9. The maximum number of electrons that the M shell (n = 3) can hold is:

8 18 2 32

Explanation: Maximum electrons in a shell = 2n² = 2 × 3² = 18.

10. The electronic configuration of sodium (Z = 11) is:

2, 8, 2 2, 9 2, 8, 1 2, 7, 2

Explanation: Sodium has one electron in the outermost shell, so its valency is 1 and it forms Na⁺ by losing that electron.

11. How many valence electrons does a chlorine atom (Z = 17) have?

5 6 8 7

Explanation: Chlorine's configuration is 2, 8, 7, so it has seven valence electrons and gains one electron to form Cl⁻.

12. According to Bohr's model, an electron revolving in a stationary orbit:

continuously emits energy moves inside the nucleus has variable energy does not radiate energy

Explanation: Bohr proposed that electrons in discrete stationary orbits have fixed energy and do not radiate; energy is absorbed or emitted only when jumping between orbits.

13. The main drawback of Rutherford's atomic model was that it:

did not recognise the nucleus could not explain the stability of the atom denied the existence of electrons placed neutrons in orbits

Explanation: A revolving charged electron should radiate energy and spiral into the nucleus, which would make atoms unstable; Bohr's model resolved this.

14. An element with atomic number 18 belongs to which group of elements?

Noble gases Halogens Alkali metals Alkaline earth metals

Explanation: Z = 18 is argon (2, 8, 8) with a complete octet, hence a noble gas.

15. The pH of pure water at 25 °C is:

7 1 10 14

Explanation: Pure water is neutral with [H⁺] = [OH⁻] = 10⁻⁷ M, giving pH 7.

16. Which acid is present in lemon and other citrus fruits?

Acetic acid Citric acid Tartaric acid Oxalic acid

Explanation: Citrus fruits such as lemon and orange contain citric acid, giving their sour taste.

17. Vinegar is a dilute solution of:

Acetic acid Citric acid Formic acid Lactic acid

Explanation: Vinegar contains about 5–8% acetic (ethanoic) acid in water.

18. The sour taste of tamarind is mainly due to:

Lactic acid Malic acid Tartaric acid Oxalic acid

Explanation: Tamarind contains tartaric acid. Lactic acid is in curd, malic acid in apple, oxalic acid in tomato/spinach.

19. Which of the following turns red litmus paper blue?

Dilute hydrochloric acid Vinegar Lemon juice A base such as sodium hydroxide

Explanation: Bases turn red litmus blue, whereas acids turn blue litmus red.

20. Milk of magnesia, used as an antacid, is chemically:

Magnesium sulphate Magnesium hydroxide Magnesium carbonate Calcium hydroxide

Explanation: Mg(OH)₂ is a mild base that neutralises excess hydrochloric acid in the stomach, relieving acidity.

21. The chemical formula of washing soda (sodium carbonate crystals) is:

Na₂CO₃·10H₂O NaHCO₃ Na₂CO₃·H₂O NaOH

Explanation: Washing soda is sodium carbonate decahydrate, containing 10 molecules of water of crystallisation. NaHCO₃ is baking soda.

22. Bleaching powder is produced by passing chlorine gas over:

quicklime solution limestone dry slaked lime, Ca(OH)₂ sodium hydroxide

Explanation: Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O. Bleaching powder is used for disinfecting water and bleaching textiles.

23. Plaster of Paris is chemically:

Calcium sulphate hemihydrate (CaSO₄·½H₂O) Calcium sulphate dihydrate Calcium carbonate Calcium oxide

Explanation: It is obtained by heating gypsum (CaSO₄·2H₂O) at about 373 K and sets into a hard mass when mixed with water.

24. Rain water is called acid rain when its pH falls below:

7.0 5.6 6.5 8.2

Explanation: Natural rain is slightly acidic (about 5.6) due to dissolved CO₂; a pH below 5.6 indicates acid rain caused by SO₂ and NO₂.

25. An aqueous solution of NaCl, a salt of a strong acid and a strong base, is:

strongly acidic basic neutral (pH ≈ 7) weakly acidic

Explanation: NaCl does not undergo hydrolysis, so its solution remains neutral.

SECTION II: Metals & Non-metals, Elements, Compounds & Mixtures [Questions 26 to 50]

26. The most abundant metal in the Earth's crust is:

Iron Calcium Sodium Aluminium

Explanation: Aluminium makes up about 8% of the crust by mass, the most abundant metal; iron is second.

27. The most abundant element in the Earth's crust by mass is:

Oxygen Silicon Aluminium Iron

Explanation: Oxygen forms about 46% of the crust by mass, followed by silicon, aluminium and iron.

28. Which metal is liquid at room temperature?

Lead Sodium Mercury Zinc

Explanation: Mercury has a melting point of −39 °C and is the only common metal that is liquid at room temperature.

29. The best conductor of electricity among all metals is:

Copper Gold Aluminium Silver

Explanation: Silver has the highest electrical conductivity; copper, being cheaper, is the most widely used conductor.

30. Which non-metal is a good conductor of electricity?

Diamond Graphite Sulphur Phosphorus

Explanation: Graphite has free delocalised electrons between its layers, so it conducts electricity.

31. The most malleable and ductile metal is:

Silver Copper Gold Aluminium

Explanation: Gold can be beaten into extremely thin sheets and drawn into very fine wires.

32. Sodium is stored under kerosene oil because it:

reacts vigorously with air and moisture is radioactive is a liquid evaporates readily

Explanation: Sodium is highly reactive and catches fire in moist air, so kerosene keeps it isolated.

33. Which element is stored under water to prevent it from catching fire in air?

Sodium Magnesium White phosphorus Sulphur

Explanation: White phosphorus ignites spontaneously in air at about 35 °C, so it is kept under water.

34. Brass is an alloy of:

Copper and tin Copper and zinc Lead and tin Iron and carbon

Explanation: Brass = Cu + Zn, used for utensils, musical instruments and fittings.

35. Bronze is an alloy of:

Copper and zinc Copper and tin Zinc and tin Aluminium and magnesium

Explanation: Bronze = Cu + Sn, used for statues, medals and bells.

36. Stainless steel is an alloy of iron with:

copper and zinc lead and tin aluminium and magnesium chromium and nickel

Explanation: Chromium and nickel make steel resistant to rusting and corrosion.

37. Coating iron with a thin layer of zinc to protect it from rusting is called:

Anodising Tempering Galvanisation Roasting

Explanation: Zinc, being more reactive than iron, protects the iron underneath even if the coating is scratched.

38. In the thermite reaction, aluminium powder reduces:

iron(III) oxide sodium chloride calcium carbonate copper sulphate

Explanation: 2Al + Fe₂O₃ → Al₂O₃ + 2Fe + heat. The molten iron is used to weld railway tracks.

39. Aqua regia, which can dissolve gold and platinum, is a mixture of:

conc. HNO₃ and conc. HCl in the ratio 3 : 1 conc. HCl and conc. HNO₃ in the ratio 3 : 1 conc. H₂SO₄ and conc. HCl in the ratio 3 : 1 conc. HCl and acetic acid in the ratio 1 : 1

Explanation: Aqua regia (royal water) is 3 parts conc. HCl to 1 part conc. HNO₃.

40. Which of the following metals is the most reactive?

Zinc Iron Sodium Copper

Explanation: In the reactivity series: Na > Zn > Fe > Cu.

41. The chief ore of aluminium is:

Haematite Bauxite Cinnabar Galena

Explanation: Bauxite (Al₂O₃·2H₂O) is the main ore. Haematite is iron ore, cinnabar is mercury ore and galena is lead ore.

42. The principal ore of mercury is:

Galena (PbS) Zinc blende (ZnS) Haematite (Fe₂O₃) Cinnabar (HgS)

Explanation: Cinnabar is mercury(II) sulphide; heating it in air yields mercury.

43. Which non-metal exists as a liquid at room temperature?

Iodine Chlorine Sulphur Bromine

Explanation: Bromine is a reddish-brown volatile liquid; iodine is a solid and chlorine a gas at room temperature.

44. Which of the following is a metalloid?

Sodium Carbon Silicon Sulphur

Explanation: Silicon shows properties of both metals and non-metals and is a semiconductor.

45. Which of the following is a mixture?

Ammonia Carbon dioxide Sodium chloride Air

Explanation: Air is a homogeneous mixture of gases (N₂, O₂, Ar, CO₂ etc.) in no fixed ratio. The others are compounds.

46. Two miscible liquids with close boiling points are separated by:

fractional distillation filtration sublimation centrifugation

Explanation: A fractionating column gives repeated vaporisation and condensation, separating liquids with small boiling-point differences.

47. The different coloured components of black ink are separated by:

sublimation crystallisation chromatography magnetic separation

Explanation: Chromatography separates dissolved components based on their different rates of movement over a medium such as paper.

48. Milk is an example of a:

colloid true solution suspension pure compound

Explanation: Milk has particles that do not settle and scatter light (Tyndall effect), which is characteristic of colloids.

49. Which compound is formed by ionic bonding?

Methane Sodium chloride Water Carbon dioxide

Explanation: NaCl forms by transfer of an electron from Na to Cl. The others have covalent bonds.

50. Rust is chemically:

iron(II) sulphate iron carbonate hydrated iron(III) oxide (Fe₂O₃·xH₂O) anhydrous iron(II) chloride

Explanation: Rusting needs both oxygen and moisture, forming the reddish-brown hydrated ferric oxide.

SECTION III: Carbon & its Compounds, Oxidation & Reduction [Questions 51 to 75]

51. Which of the following is NOT an allotrope of carbon?

Diamond Graphite Fullerene Silica

Explanation: Silica is silicon dioxide (SiO₂), a compound. Diamond, graphite and fullerene are allotropes of carbon.

52. The hardest known natural substance is:

Graphite Quartz Topaz Diamond

Explanation: In diamond each carbon is covalently bonded to four others in a rigid 3D network.

53. Graphite conducts electricity because it has:

free ions no covalent bonds free (delocalised) electrons a very high density

Explanation: Each carbon in graphite uses three electrons for bonding; the fourth is delocalised and carries current.

54. The shape of a C₆₀ fullerene molecule resembles a:

pyramid cube football (soccer ball) flat sheet

Explanation: Buckminsterfullerene is a hollow sphere of 60 carbon atoms arranged in pentagons and hexagons.

55. The main constituent of CNG and biogas is:

Methane Ethane Butane Propane

Explanation: Compressed natural gas and biogas are mainly methane (CH₄), the simplest hydrocarbon.

56. The chief constituent of LPG is:

Butane Methane Ethanol Acetylene

Explanation: LPG is mainly butane (with some propane), liquefied under pressure for cooking and heating.

57. Carbon shows tetravalency because it has:

four shells four protons four isotopes four electrons in its outermost shell

Explanation: Carbon (2, 4) shares its four valence electrons to form four covalent bonds.

58. The property of carbon atoms to link with one another forming long chains and rings is called:

Isomerism Polymerisation Allotropy Catenation

Explanation: Catenation, due to strong C–C bonds, gives rise to the vast number of carbon compounds.

59. The general formula of alkanes is:

CₙH₂ₙ₊₂ CₙH₂ₙ CₙH₂ₙ₋₂ CₙHₙ

Explanation: Alkanes are saturated hydrocarbons, e.g. methane CH₄ (n = 1), ethane C₂H₆ (n = 2).

60. Ethyne (acetylene), used in gas welding, belongs to which homologous series?

Alkanes Alkenes Alkynes Alcohols

Explanation: Ethyne (C₂H₂) contains a carbon–carbon triple bond and fits the alkyne formula CₙH₂ₙ₋₂.

61. Successive members of a homologous series differ by:

a –CH₃ group a –CH₂– unit an –OH group a –CO group

Explanation: Adjacent homologues differ by CH₂, i.e. 14 atomic mass units.

62. The functional group present in carboxylic acids is:

–COOH –OH –CHO –CO–

Explanation: –COOH is the carboxyl group; –OH is alcohol, –CHO is aldehyde and –CO– is ketone.

63. Pure ethanoic acid is called glacial acetic acid because it:

freezes to an ice-like solid below 16.6 °C boils at a very low temperature is found in glaciers dissolves ice

Explanation: Its melting point is 16.6 °C, so in cold weather it solidifies like ice.

64. Denatured spirit is ethanol mixed with a small quantity of:

acetic acid methanol (and a dye) glycerol ethylene glycol

Explanation: Methanol makes the alcohol poisonous so it cannot be misused as a drink; the dye helps identification.

65. The reaction of ethanol with ethanoic acid in the presence of conc. H₂SO₄ gives:

ethane ethanal ethyl ethanoate (an ester) sodium ethanoate

Explanation: This esterification produces ethyl ethanoate, a sweet fruity-smelling ester.

66. Conversion of unsaturated vegetable oils into saturated fats using a nickel catalyst is called:

Dehydrogenation Hydrogenation Saponification Fermentation

Explanation: Addition of hydrogen across double bonds in the presence of nickel gives vanaspati ghee.

67. Incomplete combustion of carbon compounds produces the poisonous gas:

carbon monoxide carbon dioxide nitrogen dioxide ozone

Explanation: In limited oxygen, carbon forms CO, which binds haemoglobin and reduces oxygen transport.

68. In terms of electron transfer, oxidation is:

gain of electrons sharing of electrons no change in electrons loss of electrons

Explanation: Oxidation is loss of electrons (OIL RIG: Oxidation Is Loss, Reduction Is Gain).

69. Reduction is best described as:

addition of oxygen removal of hydrogen loss of electrons addition of hydrogen or removal of oxygen

Explanation: Reduction involves gain of hydrogen or electrons, or loss of oxygen.

70. An oxidising agent is a substance that:

donates electrons and gets oxidised accepts electrons and gets reduced always has the lowest oxidation number takes no part in redox reactions

Explanation: Oxidising agents oxidise others by accepting electrons; their own oxidation number decreases.

71. In the reaction ZnO + C → Zn + CO, the reducing agent is:

Zinc oxide Carbon Zinc Carbon monoxide

Explanation: Carbon removes oxygen from ZnO (is itself oxidised to CO), so it is the reducing agent.

72. In the reaction CuO + H₂ → Cu + H₂O, which substance is oxidised?

Hydrogen Copper(II) oxide Copper Water

Explanation: Hydrogen gains oxygen to form water (oxidation), while CuO loses oxygen (reduction).

73. The oxidation number of manganese in KMnO₄ is:

+7 +2 +4 +6

Explanation: K (+1) + Mn + 4(−2) = 0, so Mn = +7.

74. Rancidity of fats and oils is mainly caused by:

reduction oxidation evaporation sublimation

Explanation: Oxidation produces foul-smelling compounds; antioxidants or nitrogen flushing (as in chips packets) prevent it.

75. Burning of magnesium ribbon in air to form magnesium oxide is an example of:

a decomposition reaction an oxidation (combination) reaction a displacement reaction a neutralisation reaction

Explanation: 2Mg + O₂ → 2MgO, burning with a dazzling white flame, is both combination and oxidation.

SECTION IV: Air, Water, Fertilizers, Soap, Glass & Everyday Chemistry [Questions 76 to 100]

76. Approximately what percentage of dry air is nitrogen by volume?

21% 78% 0.93% 0.04%

Explanation: Dry air is about 78% nitrogen, 21% oxygen, 0.93% argon and 0.04% carbon dioxide.

77. Oxygen constitutes about what percentage of the atmosphere by volume?

78% 9% 21% 0.04%

Explanation: Oxygen is the second most abundant gas, at about 21% by volume.

78. The third most abundant gas in dry air is:

Carbon dioxide Neon Argon Helium

Explanation: Argon (about 0.93%) follows nitrogen and oxygen.

79. The gas commonly used in fire extinguishers is:

Carbon dioxide Hydrogen Oxygen Methane

Explanation: CO₂ is denser than air and does not support combustion, so it smothers the fire.

80. Depletion of the ozone layer is mainly caused by:

chlorofluorocarbons (CFCs) carbon monoxide argon water vapour

Explanation: CFCs release chlorine atoms in the stratosphere that break down ozone; the Montreal Protocol phases them out.

81. Which of the following is NOT a greenhouse gas?

Carbon dioxide Methane Nitrous oxide Nitrogen (N₂)

Explanation: N₂ does not absorb infrared radiation significantly, unlike CO₂, CH₄ and N₂O.

82. Acid rain is mainly caused by oxides of:

carbon and hydrogen calcium and magnesium sodium and potassium sulphur and nitrogen

Explanation: SO₂ and NO₂ dissolve in rain water forming sulphuric and nitric acids.

83. Laughing gas is:

Nitric oxide (NO) Nitrogen dioxide (NO₂) Ammonia (NH₃) Nitrous oxide (N₂O)

Explanation: Nitrous oxide is used as a mild anaesthetic, especially in dentistry.

84. In the manufacture of cement, gypsum is added to:

slow down the setting of cement make it set instantly give it colour make it dissolve in water

Explanation: Without gypsum, cement would set too quickly to be worked. It is added to the clinker at the grinding stage.

85. Hardness of water is caused by dissolved salts of:

sodium and potassium aluminium and lead silicon and boron calcium and magnesium

Explanation: Bicarbonates, chlorides and sulphates of calcium and magnesium make water hard and prevent soap from lathering.

86. Temporary hardness of water, caused by bicarbonates, can be removed by:

adding common salt simple filtration boiling adding chlorine

Explanation: Boiling decomposes calcium and magnesium bicarbonates into insoluble carbonates that settle.

87. Permanent hardness of water can be removed by adding:

common salt washing soda (Na₂CO₃) chlorine alum

Explanation: Sodium carbonate precipitates Ca²⁺ and Mg²⁺ as insoluble carbonates.

88. Water has its maximum density at:

0 °C 10 °C 4 °C 100 °C

Explanation: Water's anomalous expansion makes it densest at 4 °C, so lakes freeze from the top, protecting aquatic life.

89. Heavy water (D₂O) is used in nuclear reactors as a:

moderator fuel control rod radiation shield

Explanation: Heavy water slows down fast neutrons so they can sustain the fission chain reaction.

90. Chlorination of drinking water is done to:

remove hardness kill disease-causing germs remove dissolved gases add taste

Explanation: Chlorine or bleaching powder disinfects water by destroying bacteria and other microorganisms.

91. Which fertilizer has the highest nitrogen content?

Ammonium sulphate Ammonium nitrate Calcium ammonium nitrate Urea

Explanation: Urea, CO(NH₂)₂, contains about 46% nitrogen, the highest among common solid nitrogenous fertilizers.

92. The three primary nutrients supplied by NPK fertilizers are:

nitrogen, phosphorus and calcium nitrogen, sulphur and potassium carbon, phosphorus and potassium nitrogen, phosphorus and potassium

Explanation: NPK stands for the symbols N, P and K, the three major plant nutrients.

93. Single super phosphate is a:

nitrogenous fertilizer phosphatic fertilizer potassic fertilizer micronutrient fertilizer

Explanation: Single super phosphate supplies phosphorus (as soluble phosphate) to crops.

94. Soaps are sodium or potassium salts of:

long-chain fatty acids mineral acids benzene sulphonic acids amino acids

Explanation: Soap is made from fatty acids such as stearic, palmitic and oleic acids; salts of sulphonic acids are detergents.

95. Soap is manufactured by the alkaline hydrolysis of fats and oils, a process known as:

Esterification Saponification Hydrogenation Fermentation

Explanation: Fat + NaOH → soap + glycerol. Glycerol is recovered as a by-product.

96. Detergents are preferred over soaps for washing in hard water because:

they increase water hardness they do not dissolve in water they react with oil to form acids they do not form insoluble scum with Ca²⁺ and Mg²⁺ ions

Explanation: Calcium and magnesium salts of detergents are soluble, so no scum forms and cleaning remains effective.

97. Soap removes dirt from clothes by forming:

micelles precipitates polymers calcium salts

Explanation: Hydrophobic tails of soap anions trap oily dirt while hydrophilic heads face the water, forming micelles that are rinsed away.

98. The main raw materials of ordinary soda-lime glass are:

silica, borax and lead oxide clay, gypsum and lime silica (sand), sodium carbonate and limestone sand, cement and coke

Explanation: Sand, soda ash and limestone are melted together at high temperature to make common window and bottle glass.

99. Which compound imparts a blue colour to glass?

Cobalt oxide Chromium oxide Manganese dioxide Gold chloride

Explanation: Cobalt oxide gives blue; chromium gives green, manganese dioxide gives purple and colloidal gold gives ruby red.

100. Heat-resistant laboratory glassware (Pyrex) is made of:

soda-lime glass lead (flint) glass optical crown glass borosilicate glass

Explanation: Borosilicate glass contains boron oxide, giving a low coefficient of thermal expansion so it withstands sudden temperature changes.

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