THE UNKNOWN SOLUTION TEAM

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*TAKE NOTE*

*WAEC releases 2025 private WASSCE results( WAEC GCE)* The West African Examinations Council (WAEC) has released the 2025 computer-based West African Senior School Certificate Examination (CB-WASSCE) results for private candidates’ second series. According to a statement issued by Moyosola Adesina, the Ag. head of public affairs, for the head of national office at WAEC, on Monday, a total of 33,989 out of the 65,752 candidates that sat the examination, which represents 51.69 percent obtained credit and above in a minimum of five subjects with or without English Language and/or Mathematics. The analysis of the statistics of the candidates’ performance further shows 27,727 candidates representing 42.17 percent obtained credit and above in a minimum of five subjects, including English Language and Mathematics. The outcome offers fresh insight into the performance trend of private candidates, highlighting both progress and areas that require sustained academic support and policy attention. The examination which took place in Nigeria between Tuesday, November 11 and Wednesday, December 17, 2025, had 69,604 candidates, representing a 1.8 percent increase, when compared with the 2024 entry figure of 68,342, enrolled for the examination, while 65,752 candidates sat the examination at 370 centres spread across the country. WAEC explained that out of the total number of 61,943 candidates that sat the examination, which represents 94.21 percent have their results fully processed and released while 3,809 candidates, that is 5.79 percent have a few of their subjects still being processed due to some errors traceable to them. Of the total number of 65,752 candidates that sat the examination, 32,005 were males while 33,747 were females, representing 48.68 percent and 51.32 percent respectively. Amongst the candidates that sat the examination, 235 candidates, with varying degrees of Special Needs, registered for the examination. Out of this number, three were visually impaired, 24 had impaired hearing, and three were Albinos. All these candidates with special needs were adequately provided for in the administration of the examination.Of this number, 13,416, that is 48.39 percent were male candidates, while 14,311, representing 51.61 percent were female candidates. The percentage of candidates in this category in the WASSCE for Private Candidates, 2023 and 2024, second series, that is, those who obtained credit and above in a minimum of five subjects, including English Language and Mathematics, were 44.29 percent, and 53.64 percent, respectively. Thus, there is a marginal decrease of 11.47 percent in performance in this regard. This analysis, however, cannot be compared with that of WASSCE for School Candidates, as the population for this examination consists of candidates who are outside the school system. 1,899 candidates’ results, representing 2.89 percent of the total number of candidates that sat the examination, are being withheld in connection with various reported cases of examination malpractice. The cases are being investigated and reports of the investigations will be presented to the appropriate committee of the council for determination. The Committee’s decisions will be communicated directly to the affected candidates, thereafter WAEC counsels candidates to check their results by visiting www.waecdirect.org

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Quartz crystals are piezoelectric. This property is used in A) Oscillators B) Radio transmitters C) Watches D) All of these Answer: D --- 132. Which form of silica is used for making optical fibres? A) Quartz B) Fused silica C) Cristobalite D) Tridymite Answer: B --- 133. Kieselguhr is a A) Porous diatomaceous earth B) Crystalline quartz C) Amorphous carbon D) Hydrated sodium silicate Answer: A --- 134. The main constituent of diatom shells is A) CaCO₃ B) SiO₂ C) MgCO₃ D) Organic matter Answer: B --- 135. The reaction Si + 2Cl₂ → SiCl₄ shows silicon can act as A) Oxidising agent B) Reducing agent C) Both D) None Answer: B --- 136 – 139 --- 136. Silicon tetrachloride is a A) Liquid that fumes in moist air B) Solid C) Gas D) Non-reactive compound Answer: A --- 137. Silicon does NOT form graphite-like structure because A) It is larger in size B) It has d-orbitals C) Both D) It is more metallic Answer: C --- 138. The bond in SiO₂ is A) 50% ionic, 50% covalent B) Purely covalent C) Highly covalent with some ionic character D) Metallic Answer: C --- 139. Which is the hardest known material after diamond? A) SiC B) B₄C C) Both A and B D) Al₂O₃ Answer: C

101. Silicon(IV) oxide reacts with Na₂CO₃ on strong heating to form A) Na₄SiO₄ + CO₂ B) Na₂SiO₃ + CO₂ C) Na₂SiO₄ + CO₂ D) NaSiO₃ + CO₂ Answer: B --- 102. The compound commonly known as “silica” is A) SiO B) SiO₂ C) Si₂O₃ D) Si₃O₄ Answer: B --- 103. Which form of silica has a very low coefficient of expansion? A) Quartz B) Fused silica C) Tridymite D) Cristobalite Answer: B --- 104. Silica gel is represented as A) SiO₂·nH₂O B) SiO₂ only C) Na₂SiO₃·nH₂O D) Al₂SiO₅ Answer: A --- 105. The main use of silica gel in industry is as a A) Dehydrating agent B) Catalyst C) Adsorbent for gases/vapours D) All of these Answer: D --- 106. Which is NOT a natural form of silica? A) Quartz B) Flint C) Opal D) Silica gel Answer: D --- 107. Silicon carbide (SiC) is also called A) Carborundum B) Moissanite C) Both A and B D) Corundum Answer: C --- 108. The reaction SiO₂ + 3C → SiC + 2CO takes place at A) 500 °C B) 1000 °C C) Very high temperature D) Room temperature Answer: C --- 109. Water-glass on strong heating with sodium hexafluorosilicate(IV) gives A) Silica gel B) Glass C) Sodium fluoride D) Silicon carbide Answer: A --- 110. Which glass is used for making chemical laboratory apparatus? A) Soda-lime glass B) Flint glass C) Borosilicate (Pyrex) glass D) Lead crystal glass Answer: C --- 111. The approximate composition of Pyrex glass is A) SiO₂ 80%, B₂O₃ 12%, Al₂O₃ + Na₂O rest B) SiO₂ 100% C) SiO₂ 60%, PbO 30% D) SiO₂ 55%, Na₂O 30% Answer: A --- 112. Flint glass is heavy and brilliant because it contains A) Lead oxide B) Boron oxide C) Aluminium oxide D) Iron oxide Answer: A --- 113. The softening point of ordinary soda-lime glass is around A) 300–400 °C B) 600–800 °C C) 1000 °C D) 1500 °C Answer: B --- 114. Glass turns into a super-cooled liquid because A) It has no sharp melting point B) It is amorphous C) Molecules are randomly arranged D) All of these Answer: D --- 115. Which type of glass is used for making prisms and achromatic lenses? A) Soda-lime B) Pyrex C) Flint D) Quartz Answer: C --- 116. Coloured glasses are obtained by adding small amounts of A) Transition metal oxides B) Alkali metals C) Carbon D) Sulphur Answer: A --- 117. The purest form of clay used for porcelain is A) Fire clay B) Ball clay C) Kaolin (China clay) D) Bentonite Answer: C --- 118. Cement is manufactured by strongly heating a mixture of A) Clay + limestone B) Sand + limestone C) Clay + gypsum D) Clay + coke Answer: A --- 119. Zeolites are basically A) Hydrated sodium aluminosilicates B) Anhydrous calcium silicates C) Pure silica D) Silicon carbide Answer: A --- 120. Zeolites are widely used as A) Water softeners B) Molecular sieves C) Ion-exchange resins D) All of these Answer: D --- 121 – 135 --- 121. Which of the following is an acidic oxide? A) Na₂O B) CO₂ C) SiO₂ D) CaO Answer: C --- 122. Silicon(IV) oxide reacts with HF to form A) SiF₄ B) H₂SiF₆ C) SiCl₄ D) SiH₄ Answer: B --- 123. Silicon does not react with dilute acids but reacts with A) Hot concentrated NaOH B) Cold dilute NaOH C) HCl D) HNO₃ Answer: A --- 124. The gas evolved when silicon reacts with hot concentrated NaOH is A) O₂ B) H₂ C) CO₂ D) N₂ Answer: B --- 125. Very pure silicon for semiconductors is obtained by A) Zone refining B) Reduction with carbon C) Heating with Mg D) Direct fusion Answer: A --- 126. Silicon is used in A) Steel alloys B) Bronze C) Solar cells D) All of these Answer: D --- 127. Which is NOT a use of silicones? A) Lubricants B) Water repellents C) Electrical insulators D) Abrasives Answer: D --- 128. Silicon shows a valency of A) 2 only B) 4 only C) 2 and 4 D) 6 Answer: B --- 129. The structure of silicones is A) –Si–O–Si–O– chain with organic groups B) Pure SiO₂ network C) Si–Si chains D) Ring structure Answer: A --- 130. Silica is used in the lining of furnaces because it is A) Heat resistant B) Acid resistant C) Both A and B D) Cheap Answer: C --- 131.

Silicon does not occur free in nature but as A) SiO₂ and silicates B) Silicon carbide C) Silicon nitride D) All of these Answer: A --- 92. The reaction SiO₂ + 3C → SiC + 2CO produces A) Silicon B) Silicon carbide C) Silicon nitride D) Silane Answer: B --- 93. Silica gel packets say “Do not eat” because they are A) Poisonous B) Hygroscopic C) Radioactive D) Explosive Answer: B --- 94. Graphite does not react with chlorine but silicon does because A) Silicon has vacant d-orbitals B) Silicon is smaller C) Graphite is more stable D) Chlorine is inert Answer: A --- 95. Silicon forms A) Silicides with metals B) Silicates with metal oxides C) Both A and B D) None Answer: C --- 96. The structure of quartz is A) Three-dimensional network B) Layer structure C) Chain structure D) Discrete molecules Answer: A --- 97. Ordinary glass is softened and shaped by A) Blowing B) Pressing C) Both A and B D) Only melting Answer: C --- 98. Annealing of glass is done to A) Remove internal stress B) Cool slowly and uniformly C) Prevent cracking D) All of these Answer: D --- 99. Lime-soda glass cracks easily on sudden temperature change because A) High coefficient of expansion B) Low silica content C) Presence of sodium D) All of these Answer: A --- 100. The reaction 2KOH(aq) + SiO₂(s) → K₂SiO₃(aq) + H₂O(l) shows that silica is A) Acidic oxide B) Basic oxide C) Amphoteric D) Neutral Answer: A

61. The formula of water-glass is A) Na₂SiO₃ B) Na₄SiO₄ C) Na₂SiO₄ D) Na₂Si₂O₅ Answer: A --- 62. Sodium trioxosilicate(IV) is obtained by fusing A) Sand + Na₂CO₃ B) Sand + NaOH C) Sand + NaCl D) Sand + Na₂SO₄ Answer: A --- 63. Water-glass forms a viscous liquid in hot water under pressure and is used as A) Adhesive B) Fire-proofing agent C) Egg preservative D) All of these Answer: D --- 64. On acidification, water-glass sets into a gel known as A) Silica gel B) Silicone gel C) Boron gel D) Alum gel Answer: A --- 65. Silica gel is a good absorbent for A) Water vapour B) Valuable vapours in industry C) Petrol refining D) All of these Answer: D --- 66. The purest form of clay used for making porcelain is A) Kaolin B) Bentonite C) Fire clay D) Ball clay Answer: A --- 67. Cement is made by heating clay with A) Limestone B) Sand C) Gypsum D) Coke Answer: A --- 68. Glass is regarded as a super-cooled liquid because A) It is amorphous B) Molecules are randomly arranged C) It flows very slowly D) All of these Answer: D --- 69. The softening of glass before melting is an important property because A) It allows shaping B) Prevents cracking C) Both A and B D) None Answer: C --- 70. Heat-resistant glass (Pyrex) has a low coefficient of expansion due to A) High silica and boron content B) Lead oxide C) Sodium oxide D) Calcium oxide Answer: A --- 71. Quartz crystals are used for A) Optical instruments B) Frequency control in radio transmitters C) Ultraviolet lamps D) All of these Answer: D --- 72. Silicon tetrachloride is prepared by A) Direct combination of Si and Cl₂ B) Action of HCl on SiO₂ C) Both A and B D) None Answer: C --- 73. Silicon tetrachloride reacts with water to form A) Silica and HCl B) Silicic acid and HCl C) Both A and B D) Only silica Answer: C --- 74. Silicon is more reactive than graphite because A) It has vacant d-orbitals B) It is larger in size C) Lower ionization energy D) All of these Answer: A --- 75. Silicon does not form multiple bonds easily because A) d-orbitals are not suitable for effective π-overlap B) It is too small C) High electronegativity D) Metallic nature Answer: A --- 76. Silicon reacts with hot concentrated alkali as A) Si + 2NaOH + H₂O → Na₂SiO₃ + 2H₂ B) No reaction C) Forms silicate only D) Forms oxide Answer: A --- 77. Silicon(IV) oxide is insoluble in water due to A) Giant covalent network B) Strong Si–O bonds C) High lattice energy D) All of these Answer: D --- 78. Fused quartz is transparent to A) Ultraviolet light B) Infrared light C) Visible light D) All of these Answer: D (especially UV) --- 79. Kieselguhr is used in making A) Dynamite B) Filters C) Polishing powders D) All of these Answer: D --- 80. The formula of sodium trioxosilicate(IV) is A) Na₂SiO₃ B) Na₄SiO₄ C) Na₂SiO₄ D) NaSiO₃ Answer: A --- 81. Flint glass has high refractive index due to A) Lead oxide B) Boron oxide C) Aluminium oxide D) Calcium oxide Answer: A --- 82. Pyrex glass contains approximately A) 80% SiO₂, 12% B₂O₃, small Al₂O₃ and Na₂O B) 100% SiO₂ C) 60% SiO₂, 40% PbO D) 50% SiO₂, 50% Na₂O Answer: A --- 83. Coloured glass is produced by adding A) Metallic oxides B) Carbon C) Sulphur D) Chlorine Answer: A --- 84. Clay is mainly A) Hydrated aluminium trioxosilicate(IV) B) Pure silica C) Calcium silicate D) Sodium silicate Answer: A --- 85. Zeolites are used as A) Water softeners B) Molecular sieves C) Ion-exchangers D) All of these Answer: D --- 86. Silicon carbide is also called A) Carborundum B) Moissanite C) Both A and B D) Silica Answer: C --- 87. Silicon carbide is A) Very hard B) Used as abrasive C) High melting point D) All of these Answer: D --- 88. Silicones are A) Polymers of R₂SiO units B) Water repellent C) Heat resistant D) All of these Answer: D --- 89. Very pure silicon is manufactured by A) Zone refining B) Heating SiCl₄ with Zn or H₂ C) Both A and B D) Direct carbon reduction Answer: C --- 90. Silicon is a A) Metal B) Non-metal C) Metalloid D) Inert gas Answer: C --- 91.

*CONTINUETION* 31. The most common trioxosilicates(IV) in Earth’s crust are those of A) Sodium and potassium B) Calcium and magnesium C) Iron and aluminium D) All of these Answer: D --- 32. Ordinary glass is also called A) Flint glass B) Pyrex glass C) Lime-soda glass D) Quartz glass Answer: C --- 33. Lime-soda glass is made from a mixture of A) SiO₂ + Na₂CO₃ + CaCO₃ B) SiO₂ + B₂O₃ + Al₂O₃ C) SiO₂ + PbO D) Pure SiO₂ Answer: A --- 34. The reaction for making lime-soda glass is A) Na₂CO₃ + SiO₂ → Na₂SiO₃ + CO₂ B) CaCO₃ + SiO₂ → CaSiO₃ + CO₂ C) Both A and B D) None Answer: C --- 35. Ordinary glass softens at about A) 500 °C  B) 800 °C  C) 1200 °C  D) 1500 °C Answer: B --- 36. Glass does not have a sharp melting point because A) It is amorphous B) It is crystalline C) It is a metal D) It is ionic Answer: A --- 37. Flint glass contains A) Lead silicate B) Boron oxide C) Aluminium oxide D) Pure silica Answer: A --- 38. Flint glass is used for making A) Laboratory apparatus B) Prisms and lenses C) Ovenware D) Optical fibres Answer: B --- 39. Pyrex glass contains about A) 80% SiO₂, 12% B₂O₃ B) 100% SiO₂ C) 50% SiO₂, 50% PbO D) 70% SiO₂, 30% Na₂O Answer: A --- 40. Pyrex glass is an example of A) Heat-resistant glass B) Coloured glass C) Soft glass D) Flint glass Answer: A --- 41. Coloured glass is obtained by adding small quantities of A) Metallic oxides B) Carbon C) Sulphur D) Chlorine Answer: A --- 42. Clay is formed by the weathering of A) Carbonates B) Silicate rocks C) Sulphides D) Oxides Answer: B --- 43. The purest form of clay is A) Kaolin B) Bentonite C) Fire clay D) Fuller's earth Answer: A --- 44. Clay is used in making A) Pottery and ceramics B) Tiles and bricks C) Cement D) All of these Answer: D --- 45. Zeolites are A) Aluminosilicates B) Used as water softeners C) Used in ion-exchange D) All of these Answer: D --- 46. Sodium aluminium trioxosilicate(IV) is used as A) Water softener B) Detergent builder C) Resin in ion-exchange D) All of these Answer: D --- 47. Silicon(IV) oxide reacts with concentrated NaOH to form A) Na₄SiO₄ + H₂O B) Na₂SiO₃ + H₂O C) Na₂SiO₄ + H₂ D) NaSiO₃ + H₂O Answer: B --- 48. Silicon carbide is also known as A) Carborundum B) Silica gel C) Quartz D) Kieselguhr Answer: A --- 49. Silicon does not show positive oxidation state higher than A) +2  B) +4  C) +6  D) +8 Answer: B --- 50. Silicon forms a macromolecular compound with oxygen atoms linked tetrahedrally in A) Quartz B) Tridymite C) Cristobalite D) All of these Answer: D --- 51. Silicon(IV) oxide is an acidic oxide because A) It reacts with bases B) It has high melting point C) It is insoluble in water D) It is white Answer: A --- 52. Silicon(IV) oxide reacts with hot concentrated KOH to form A) K₂SiO₃ + H₂O B) K₄SiO₄ + H₂O C) K₂SiO₄ + H₂ D) KSiO₃ + H₂O Answer: A --- 53. When silica gel is heated strongly, it forms A) Glass-like solid B) Water C) Silicone D) Silicon carbide Answer: A --- 54. Kieselguhr absorbs liquids readily and is used as A) Absorbent for nitroglycerine (dynamite) B) Filter C) Drying agent D) All of these Answer: D --- 55. The structure of silicon(IV) oxide is A) Chain B) Layer C) Three-dimensional network D) Discrete molecules Answer: C --- 56. Silicones are polymers of A) R₂SiO units B) RSiO units C) SiO₂ units D) R₄Si units Answer: A --- 57. Silicones are chemically A) Inert B) Water repellent C) Heat resistant D) All of these Answer: D --- 58. The reaction SiO₂ + 2C → Si + 2CO is carried out in A) Blast furnace B) Electric furnace C) Reverberatory furnace D) Open hearth furnace Answer: B --- 59. Silicon is used for making A) Transistors B) Solar cells C) Integrated circuits D) All of these Answer: D --- 60. Silicon is a A) Metal B) Non-metal C) Metalloid D) Noble gas Answer: C

Powdered quartz is used in making A) Silicon carbide B) Silicon tetrachloride C) Sodium trioxosilicate(IV) D) All of these Answer: D --- 30. Trioxosilicates(IV) are salts of A) H₂SiO₃ B) H₄SiO₄ C) H₂SiO₄ D) HSiO₃ Answer: A

*SILICON* 1. Silicon belongs to which group in the periodic table? A) Group 13  B) Group 14  C) Group 15  D) Group 16 Answer: B --- 2. Silicon is the ___ most abundant element in the Earth’s crust. A) First  B) Second  C) Third  D) Fourth Answer: B --- 3. Naturally occurring silicon exists mainly as A) Free element B) Silicon(IV) oxide and silicates C) Silicon carbide D) Silicon tetrachloride Answer: B --- 4. The common crystalline forms of silica are A) Quartz, Tridymite, Cristobalite B) Diamond, Graphite, Fullerene C) Calcite, Aragonite, Marble D) Rutile, Anatase, Brookite Answer: A --- 5. Silica gel is obtained by A) Heating sand B) Acidification of water-glass solution C) Burning silicon in oxygen D) Reducing SiO₂ with carbon Answer: B --- 6. Silica gel is commonly used in packaging of electronic items because A) It keeps away rats and cockroaches B) It is stable in porous packs C) It is hygroscopic D) Carbon and silicon have similar chemistry Answer: C --- 7. Silicon(IV) oxide is also known as A) Sand B) Silica C) Quartz D) All of these Answer: D --- 8. Silicon(IV) oxide is insoluble in water and all acids except A) HCl  B) H₂SO₄  C) HNO₃  D) HF Answer: D --- 9. The reaction of SiO₂ with HF produces A) SiF₄  B) H₂SiF₆  C) SiCl₄  D) SiH₄ Answer: B --- 10. Silicon(IV) oxide dissolves in hot concentrated alkali to form A) Silicates B) Silicides C) Silicon carbide D) Silicon hydride Answer: A --- 11. The melting point of silicon(IV) oxide is about A) 500 °C  B) 1000 °C  C) 1500 °C  D) 1710 °C Answer: D (approximately 1710–1730 °C) --- 12. Fused silica is used in making A) Cement B) Laboratory apparatus C) Bricks D) Paint Answer: B --- 13. Very pure silicon (99%+) is manufactured by heating sand with excess carbon in an electric furnace. The reaction is A) SiO₂ + 2C → Si + 2CO B) SiO₂ + C → Si + CO₂ C) SiO₂ + 2Mg → Si + 2MgO D) SiO₂ + 4HCl → SiCl₄ + 2H₂O Answer: A --- 14. Amorphous silicon is prepared by A) Heating sand with magnesium B) Heating SiCl₄ with zinc C) Burning silicon in oxygen D) Reducing SiO₂ with aluminium Answer: A --- 15. Silicon does NOT exhibit the phenomenon of A) Allotropy B) Catenation C) Multiple bonding D) All of these Answer: C --- 16. Silicon is ___ reactive than carbon. A) Less  B) More  C) Equally  D) Not comparable Answer: A --- 17. When strongly heated in air, silicon forms A) SiC  B) Si₃N₄  C) SiO₂  D) SiH₄ Answer: C --- 18. Silicon decomposes steam at red heat to liberate A) Oxygen  B) Hydrogen  C) Carbon dioxide  D) Nitrogen Answer: B --- 19. Silicon combines with chlorine under similar conditions to form A) SiCl₄  B) SiH₄  C) SiO₂  D) SiC Answer: A --- 20. Graphite does NOT react with chlorine, but silicon does because A) Silicon is larger in size B) Silicon has vacant d-orbitals C) Silicon is more metallic D) Silicon has lower ionization energy Answer: B --- 21. Silicon is used in making semiconductors because A) It is cheap B) It can be very pure C) It has variable valency D) All of these Answer: D --- 22. Silicon is used in bronze and steel alloys to increase A) Tensile strength B) Ductility C) Colour D) Density Answer: A --- 23. Silicons (silicones) are A) Rubber-like liquids or solids B) Water and chemically unreactive C) Used as lubricants, water repellents, insulators D) All of these Answer: D --- 24. Silicon carbide (carborundum) is prepared by heating silica with carbon. Its formula is A) SiC  B) Si₂C  C) SiC₂  D) Si₃C Answer: A --- 25. Silicon carbide is used as A) Abrasive  B) Lubricant  C) Fertilizer  D) Pigment Answer: A --- 26. Water-glass is a A) Colloidal solution of silica B) Viscous liquid of sodium silicate C) Solid glass D) Hydrated silica Answer: B --- 27. Water-glass is used for A) Preserving eggs B) Fire-proofing wood and textiles C) Making silica garden D) All of these Answer: D --- 28. Kieselguhr is A) Pure silica B) Porous and absorbent form of silica C) Crystalline silica D) Amorphous carbon Answer: B --- 29.

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A. Cold dilute NaOH B. Hot concentrated NaOH C. Dry ammonia D. Moist ammonia Correct Answer: C --- 178. The reaction Cl₂ + 3F₂ → 2ClF₃ shows fluorine acting as A. Oxidising agent B. Reducing agent C. Both D. Neither Correct Answer: A --- 179. The halogen acid used in etching glass is A. HF B. HCl C. HBr D. HI Correct Answer: A --- 180. Chlorine is transported as A. Gas in cylinders B. Liquid in tankers C. Solid D. Solution Correct Answer: B --- 181. The compound Ca(OCl)₂ is called A. Bleaching powder B. Calcium hypochlorite C. Chloride of lime D. Both B and C Correct Answer: D --- 182. Chlorine turns moist starch-iodide paper A. Blue-black B. Red C. White D. Yellow Correct Answer: A --- 183. The final test for chloride after removing Br⁻ and I⁻ is A. Chromyl chloride test B. Silver nitrate test C. Both D. None Correct Answer: A --- 184. Chromyl chloride test gives red fumes of A. CrO₂Cl₂ B. Cl₂ C. HCl D. CrCl₃ Correct Answer: A --- 185. The halogen with the largest atomic radius is A. F B. Cl C. Br D. I Correct Answer: D --- 186. Hydrogen halides are generally prepared by A. Direct combination B. Action of conc. H₂SO₄ on NaX C. Both D. Only for HF Correct Answer: C --- 187. HF cannot be prepared using conc. H₂SO₄ because A. It reacts with glass B. CaF₂ is insoluble C. HF reduces H₂SO₄ D. HF is volatile Correct Answer: C --- 188. The reaction 2KMnO₄ + 16HCl → 2KCl + 2MnCl₂ + 5Cl₂ + 8H₂O shows HCl acting as A. Reducing agent B. Oxidising agent C. Acid only D. None Correct Answer: A --- 189. Chlorine is used as a A. Bleaching agent B. Disinfectant C. In PVC manufacture D. All of the above Correct Answer: D --- 190. The halogen that sublimes to give violet vapour is A. Cl₂ B. Br₂ C. I₂ D. F₂ Correct Answer: C --- 191. Chlorine is NOT used in A. Swimming pools B. Paper industry C. Softening water D. Making insecticides Correct Answer: C --- 192. The most stable halide ion is A. F⁻ B. Cl⁻ C. Br⁻ D. I⁻ Correct Answer: A --- 193. The reaction Cl₂ + H₂ → 2HCl is A. Photochemical B. Explosive in sunlight C. Both D. Reversible Correct Answer: C --- 194. Chlorine is a member of A. Group 1 B. Group 2 C. Group 17 D. Group 18 Correct Answer: C --- 195. The electronic configuration of chlorine is A. 2,8,7 B. 2,8,8 C. 2,7 D. 2,8,1 Correct Answer: A --- 196. Chlorine exhibits oxidation states from A. –1 to +7 B. 0 to +7 C. –1 only D. +1 only Correct Answer: A --- 197. The strongest acid among HX is A. HF B. HCl C. HBr D. HI Correct Answer: D --- 198. The weakest acid among HX is A. HF B. HCl C. HBr D. HI Correct Answer: A --- 199. Chlorine is dried in the laboratory using A. Conc. H₂SO₄ B. CaCl₂ C. P₂O₅ D. All of the above Correct Answer: A --- 200. The final product when bleaching powder is exposed to air for long is A. CaCO₃ B. CaCl₂ C. Ca(OH)₂ D. CaSO₄ Correct Answer: A