THE UNKNOWN SOLUTION TEAM

*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

.

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.

. ..

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

*CONTINUETION LAST* 150. The colour of bromine water is A. Greenish-yellow B. Reddish-brown C. Violet D. Pale yellow Correct Answer: B --- 151. Bromine is liberated when chlorine is passed through a solution of A. NaCl B. NaBr C. NaI D. NaF Correct Answer: B --- 152. Iodine is liberated from KI solution by A. Chlorine only B. Bromine only C. Both chlorine and bromine D. Fluorine only Correct Answer: C --- 153. The halogen that is a solid at room temperature is A. Fluorine B. Chlorine C. Bromine D. Iodine Correct Answer: D --- 154. The only halogen that is liquid at room temperature is A. Fluorine B. Chlorine C. Bromine D. Iodine Correct Answer: C --- 155. The solubility of halogens in water decreases in the order A. F₂ > Cl₂ > Br₂ > I₂ B. I₂ > Br₂ > Cl₂ > F₂ C. Cl₂ > Br₂ > I₂ > F₂ D. F₂ > I₂ > Br₂ > Cl₂ Correct Answer: C --- 156. The halogen with the highest electronegativity is A. Fluorine B. Chlorine C. Bromine D. Iodine Correct Answer: A --- 157. The bond energy of H–X decreases from HF to HI because A. Atomic size increases B. Electronegativity decreases C. Bond length increases D. All of the above Correct Answer: D --- 158. HF is a weak acid while HCl, HBr, and HI are strong acids because A. H–F bond is strongest B. F⁻ is smallest C. HF does not ionise completely D. All of the above Correct Answer: D --- 159. The reaction 2NaI + Cl₂ → 2NaCl + I₂ shows iodine has been A. Oxidised B. Reduced C. Displaced D. Both A and C Correct Answer: D --- 160. Chlorine reacts with excess cold dilute alkali to form A. Hypochlorite B. Chlorate(V) C. Chlorate(VII) D. Chloride only Correct Answer: A --- 161. Chlorine reacts with hot concentrated alkali to form A. Hypochlorite B. Chlorate(V) C. Chloride only D. Perchlorate Correct Answer: B --- 162. The formula of bleaching powder is A. CaOCl₂ B. Ca(OCl)Cl C. CaCl₂ D. Both A and B Correct Answer: D --- 163. Bleaching powder liberates chlorine with A. Dilute acids B. CO₂ C. Both A and B D. Water only Correct Answer: C --- 164. The test for chloride ion after adding dilute HNO₃ and AgNO₃ gives A. White ppt soluble in NH₃ B. Cream ppt sparingly soluble in NH₃ C. Yellow ppt insoluble in NH₃ D. No ppt Correct Answer: A --- 165. The test for bromide ion gives A. White ppt B. Cream/pale yellow ppt C. Bright yellow ppt D. Violet vapour Correct Answer: B --- 166. The test for iodide ion gives A. Cream ppt B. Yellow ppt insoluble in excess NH₃ C. White ppt D. Blue-black colour with starch Correct Answer: B --- 167. Chlorine water + starch-iodide paper turns A. Blue-black B. Red C. Green D. Colourless Correct Answer: A --- 168. The most powerful bleaching agent among halogens is A. Fluorine B. Chlorine C. Bromine D. Iodine Correct Answer: A --- 169. Chlorine is used in the manufacture of A. HCl B. PVC C. Chloroform D. All of the above Correct Answer: D --- 170. Hydrogen chloride gas can be distinguished from chlorine because HCl A. Gives white fumes with ammonia B. Bleaches litmus C. Is greenish-yellow D. Supports combustion Correct Answer: A --- 171. The reaction of chlorine with dry slaked lime produces A. CaCl₂ B. Bleaching powder C. Ca(ClO₃)₂ D. CaO Correct Answer: B --- 172. The formula of hypochlorous acid is A. HClO B. HClO₂ C. HClO₃ D. HClO₄ Correct Answer: A --- 173. Chlorine is a stronger oxidising agent than bromine because A. Its reduction potential is higher B. It is lighter C. It is a gas D. It is cheaper Correct Answer: A --- 174. The decreasing order of oxidising power of halogens is A. F₂ > Cl₂ > Br₂ > I₂ B. I₂ > Br₂ > Cl₂ > F₂ C. Cl₂ > F₂ > Br₂ > I₂ D. Br₂ > I₂ > Cl₂ > F₂ Correct Answer: A --- 175. Aqua regia contains A. 3 parts conc. HCl + 1 part conc. HNO₃ B. 1 part conc. HCl + 3 parts conc. HNO₃ C. Equal parts D. Only HCl Correct Answer: A --- 176. Nascent chlorine is produced in A. Laboratory preparation B. Aqua regia C. Bleaching powder + acid D. All of the above Correct Answer: D --- 177. Chlorine does NOT react with

A. Oxidising agent B. Reducing agent C. Catalyst D. Dehydrating agent Correct Answer: A --- 128. In the Downs cell, chlorine is produced at the A. Steel cathode B. Graphite anode C. Mercury cathode D. Iron cathode Correct Answer: B --- 129. Chlorine is a stronger oxidising agent than iodine because its A. Electron affinity is higher B. Atomic radius is larger C. Ionisation energy is higher D. Density is lower Correct Answer: A --- 130. The halogen that forms a pale yellow precipitate with AgNO₃ is A. Cl⁻ B. Br⁻ C. I⁻ D. F⁻ Correct Answer: B --- 131. The precipitate of AgI is A. White B. Cream C. Pale yellow D. Bright yellow Correct Answer: D --- 132. Chlorine water acts as a bleaching agent only in the presence of A. Sunlight B. Moisture C. Heat D. CO₂ Correct Answer: B --- 133. The equation for the bleaching action is A. Cl₂ + H₂O → 2HCl + [O] B. HOCl → HCl + [O] C. Both D. Neither Correct Answer: C --- 134. Chlorine is stored in amber-coloured bottles because A. It prevents decomposition by light B. It looks better C. Glass reacts D. It is cheaper Correct Answer: A --- 135. The correct products when chlorine reacts with cold dilute NaOH are A. NaCl + NaOCl + H₂O B. NaCl + NaClO₃ + H₂O C. NaClO only D. NaClO₄ Correct Answer: A --- 136. The gas that gives dense white fumes with HCl gas is A. NH₃ B. SO₂ C. CO₂ D. H₂S Correct Answer: A --- 137. Chlorine is NOT liberated when conc. HCl reacts with A. KMnO₄ B. PbO₂ C. K₂Cr₂O₇ D. NaOH Correct Answer: D --- 138. The most reactive halogen towards substitution reactions is A. Fluorine B. Chlorine C. Bromine D. Iodine Correct Answer: A --- 139. Hydrogen chloride behaves as ionic in A. Gas phase B. Aqueous solution C. Molten state D. Solid state Correct Answer: B --- 140. The only halogen acid that is a weak acid is A. HF B. HCl C. HBr D. HI Correct Answer: A --- 141. Chlorine displaces bromine from NaBr because A. Cl₂ is gas, Br₂ is liquid B. Cl₂ has higher reduction potential C. NaBr is soluble D. Bromine is coloured Correct Answer: B --- 142. The colour of iodine vapour is A. Violet B. Brown C. Purple D. Reddish Correct Answer: A --- 143. The test for chloride ions in the presence of bromide and iodide is difficult because A. All give precipitates with AgNO₃ B. AgCl is soluble C. Iodine is coloured D. Bromine is volatile Correct Answer: A --- 144. Chlorine is used as a germicide because it A. Oxidises bacteria B. Coagulates proteins C. Both D. Neither Correct Answer: C --- 145. The reaction Cl₂ + 2NaBr → 2NaCl + Br₂ is A. Redox B. Displacement C. Both D. Neutralisation Correct Answer: C --- 146. Chlorine is a non-metal because it A. Gains electrons B. Has high electronegativity C. Forms acidic oxides D. All of the above Correct Answer: D --- 147. The strongest halogen acid is A. HF B. HCl C. HBr D. HI Correct Answer: D --- 148. The weakest bond in HX is A. H–F B. H–Cl C. H–Br D. H–I Correct Answer: D --- 149. Chlorine is manufactured commercially by A. Electrolysis of brine B. Heating NaCl + MnO₂ C. Action of HCl on KMnO₄ D. All of the above Correct Answer: A

*CONTINUETION* 101. The reaction between chlorine and cold dilute NaOH produces A. NaCl + NaOCl + H₂O B. NaCl + NaClO₃ + H₂O C. NaCl + HCl D. NaClO₄ Correct Answer: A --- 102. The reaction between chlorine and hot concentrated NaOH produces A. NaCl + NaClO₃ + H₂O B. NaCl + NaOCl + H₂O C. NaCl only D. NaClO₄ Correct Answer: A --- 103. Chlorine reacts with slaked lime Ca(OH)₂ to form A. Bleaching powder B. Chalk C. Plaster of Paris D. Quicklime Correct Answer: A --- 104. Bleaching powder reacts with dilute acid to liberate A. Cl₂ B. O₂ C. HCl D. HOCl Correct Answer: A --- 105. The bleaching action of bleaching powder is due to A. Cl₂ B. Nascent oxygen C. HOCl D. Ca(OH)₂ Correct Answer: A --- 106. Chlorine oxidises bromide ions to bromine because A. Br⁻ is larger than Cl⁻ B. Chlorine is above bromine in the electrochemical series C. Bromine is a liquid D. Chlorine is green Correct Answer: B --- 107. A reddish-brown vapour evolved when chlorine water is added to KI solution is A. Bromine B. Iodine C. Hydrogen iodide D. Oxygen Correct Answer: B --- 108. Chlorine water + iodide → iodine. This shows chlorine is A. Reducing agent B. Oxidising agent C. Bleaching agent D. Dehydrating agent Correct Answer: B --- 109. The only halogen that is a good conductor of electricity in molten state is A. Chlorine B. Bromine C. Iodine D. Fluorine Correct Answer: C --- 110. Hydrogen chloride is NOT dried using A. Conc. H₂SO₄ B. P₂O₅ C. CaO D. NaOH pellets Correct Answer: C --- 111. The white precipitate formed when AgNO₃ is added to NaCl solution is A. AgCl B. AgNO₃ C. NaNO₃ D. Cl₂ Correct Answer: A --- 112. AgCl precipitate dissolves in excess A. Dilute HNO₃ B. Dilute NH₃ C. Dilute HCl D. Water Correct Answer: B --- 113. The test to distinguish chloride from iodide using Pb(CH₃COO)₂ gives A. White ppt for Cl⁻, yellow ppt for I⁻ B. Yellow ppt for Cl⁻, white ppt for I⁻ C. Both white D. Both yellow Correct Answer: A --- 114. Chlorine has strong oxidising power among halogens because it has A. Small atomic size B. High electronegativity after fluorine C. Low electron affinity D. High boiling point Correct Answer: B --- 115. The reaction 2KI + Cl₂ → 2KCl + I₂ is an example of A. Displacement B. Combination C. Neutralisation D. Decomposition Correct Answer: A --- 116. Chlorine is used in the manufacture of A. HCl B. Bleaching powder C. PVC D. All of the above Correct Answer: D --- 117. The laboratory test for HCl gas is that it A. Turns lime water milky B. Gives white fumes with ammonia C. Burns with pop sound D. Relights glowing splint Correct Answer: B --- 118. Concentrated HCl is a stronger oxidising agent than dilute HCl because A. It contains more H⁺ B. It can liberate Cl₂ C. It is denser D. It is colourless Correct Answer: B --- 119. The gas that bleaches by reduction is A. Cl₂ B. SO₂ C. O₂ D. H₂S Correct Answer: B --- 120. Chlorine reacts with turpentine (C₁₀H₁₆) to A. Burn violently B. Produce HCl C. Form addition compound D. No reaction Correct Answer: A --- 121. The colour of chlorine gas disappears when passed through heated iron filings because A. Iron is oxidised to FeCl₃ B. Chlorine is reduced C. Adsorption occurs D. Sublimation occurs Correct Answer: A --- 122. The most stable oxidation state of chlorine in its compounds is A. +7 B. +5 C. –1 D. +1 Correct Answer: C --- 123. Chlorine is NOT used for A. Sterilising swimming pools B. Making fire extinguishers C. Manufacturing dyes D. Softening hard water Correct Answer: D --- 124. The reaction Cl₂ + 8NH₃ (excess) → 6NH₄Cl + N₂ shows A. Reduction of chlorine B. Oxidation of ammonia C. Both D. Neither Correct Answer: C --- 125. The compound formed when chlorine reacts with dry slaked lime is A. CaCl₂ B. Ca(OCl)₂ C. Ca(OCl)Cl D. CaClO₃ Correct Answer: C --- 126. Hydrochloric acid reacts with ammonia solution to form white fumes of A. NH₄Cl B. NH₄OH C. NCl₃ D. HCl gas Correct Answer: A --- 127. The reaction MnO₂ + 4HCl → MnCl₂ + Cl₂ + 2H₂O shows MnO₂ acting as

The test for chloride ions using silver nitrate gives a white precipitate that is: A. soluble in excess NH₃ B. insoluble in dilute HNO₃ C. turns black in light D. soluble in excess HCl Correct Answer: A --- 28. Hydrogen chloride fumes in moist air because it: A. is dense B. reacts with water vapour C. is coloured D. is poisonous Correct Answer: B --- 29. Chlorine is used in water treatment to: A. kill germs B. remove hardness C. add taste D. colour water Correct Answer: A --- 30. Bleaching powder is chemically: A. Ca(OCl)Cl B. CaOCl₂ C. CaCl₂ D. Ca(OCl)₂ Correct Answer: B (Also written as Ca(OCl)Cl) --- 98. The reaction Cl₂ + H₂O ⇌ HCl + HOCl is favoured by: A. sunlight B. darkness and cold C. heating D. pressure Correct Answer: B --- 99. Chlorine is stored in steel cylinders under pressure in: A. gaseous form B. liquid form C. solid form D. aqueous form Correct Answer: B --- 100. The most electronegative halogen is: A. iodine B. bromine C. chlorine D. fluorine Correct Answer: D

*CHLORINE QUESTIONS* 1. Chlorine is a greenish-yellow gas with a: A. pleasant smell B. choking irritating smell C. sweet smell D. no smell Correct Answer: B --- 2. Chlorine is moderately soluble in water and the solution is called: A. chlorine water B. hydrochloric acid C. hypochlorous acid D. bleach Correct Answer: A --- 3. The laboratory preparation of chlorine uses MnO₂ + conc. HCl because MnO₂ acts as: A. catalyst B. dehydrating agent C. oxidising agent D. reducing agent Correct Answer: C --- 4. In the laboratory preparation, the all-glass apparatus is used because chlorine: A. is poisonous B. reacts with rubber/cork C. is coloured D. is dense Correct Answer: B --- 5. The gas collected by downward delivery in chlorine preparation is: A. hydrogen B. oxygen C. chlorine D. hydrogen chloride Correct Answer: C --- 6. Chlorine is dried using concentrated H₂SO₄ because: A. it is cheap B. it does not react with chlorine C. it absorbs moisture fast D. both B and C Correct Answer: D --- 7. The industrial preparation of chlorine is by: A. electrolysis of brine B. Downs process C. heating MnO₂ + HCl D. reaction of NaCl + H₂SO₄ Correct Answer: A --- 8. The anode reaction in the electrolysis of brine is: A. 2Cl⁻ → Cl₂ + 2e⁻ B. 2H₂O → O₂ + 4H⁺ + 4e⁻ C. Na⁺ + e⁻ → Na D. 2H⁺ + 2e⁻ → H₂ Correct Answer: A --- 9. Chlorine turns moist blue litmus paper: A. red then bleaches it B. permanently red C. blue D. green Correct Answer: A --- 10. The bleaching action of chlorine is due to: A. oxidation B. reduction C. chlorination D. dehydration Correct Answer: A --- 11. Chlorine water exposed to sunlight slowly turns into: A. HCl + O B. HOCl C. HCl + O₂ D. Cl₂ + H₂O Correct Answer: C --- 12. Chlorine reacts vigorously with hydrogen after: A. heating B. exposure to sunlight C. cooling D. adding catalyst Correct Answer: B --- 13. The reaction 2Fe + 3Cl₂ → 2FeCl₃ shows chlorine acting as: A. oxidising agent B. reducing agent C. bleaching agent D. catalyst Correct Answer: A --- 14. Chlorine does NOT react with dry ammonia but reacts explosively with: A. excess ammonia B. limited ammonia C. moist ammonia D. cold ammonia Correct Answer: B --- 15. When excess ammonia reacts with chlorine, the product is: A. NH₄Cl B. N₂ + HCl C. NCl₃ D. NH₂Cl Correct Answer: B --- 16. Hydrogen chloride gas is prepared in the laboratory by: A. NaCl + conc. H₂SO₄ (heat) B. MnO₂ + HCl C. electrolysis of brine D. heating NaCl alone Correct Answer: A --- 17. HCl gas turns moist blue litmus paper: A. red B. white C. colourless D. no change Correct Answer: A --- 18. The fountain experiment with HCl gas uses: A. water B. ammonia solution C. NaOH solution D. silver nitrate Correct Answer: A --- 19. HCl gas is extremely soluble in water because it: A. is polar B. reacts to form H₃O⁺ and Cl⁻ C. is light D. is coloured Correct Answer: B --- 20. Hydrochloric acid is a strong acid because it: A. is fully ionised in water B. contains chlorine C. is concentrated D. is corrosive Correct Answer: A --- 21. Dilute HCl reacts with marble chips to produce: A. CO₂ B. H₂ C. Cl₂ D. O₂ Correct Answer: A --- 22. Concentrated HCl oxidises Fe²⁺ to Fe³⁺ and itself is reduced to: A. Cl₂ B. HOCl C. Cl⁻ D. HClO₃ Correct Answer: A --- 23. Aqua regia is a mixture of conc. HCl and conc. HNO₃ in the ratio: A. 3:1 B. 1:3 C. 1:1 D. 2:1 Correct Answer: A --- 24. Aqua regia dissolves gold because it produces: A. nascent chlorine B. oxygen C. H⁺ ions D. NO₂ Correct Answer: A --- 25. Chlorine displaces iodine from KI solution because chlorine is: A. more electronegative B. stronger oxidising agent C. denser D. greener Correct Answer: B --- 26. The order of reactivity (decreasing) among halogens is: A. F > Cl > Br > I B. I > Br > Cl > F C. Cl > F > Br > I D. Br > I > Cl > F Correct Answer: A --- 27.

. .

Hydrogen resembles halogens because it: A. forms H⁻ ion B. is diatomic C. needs one electron to complete octet D. all of the above Correct Answer: D --- 166. The gas jar is inverted over the delivery tube in zinc + acid method to: A. collect hydrogen by downward displacement of water B. prevent escape of gas C. cool the gas D. dry the gas Correct Answer: A --- 167. When zinc reacts with dilute H₂SO₄, the zinc sulphate formed is: A. ZnSO₄ B. Zn₂SO₄ C. Zn(SO₄)₂ D. ZnSO₃ Correct Answer: A --- 168. The common impurity removed by passing hydrogen through acidified copper(II) sulphate solution is: A. H₂S B. AsH₃ C. PH₃ D. all of the above Correct Answer: D --- 169. Hydrogen is a better reducing agent than carbon monoxide at high temperature because: A. it is lighter B. reaction is more exothermic C. it is cheaper D. it is pure Correct Answer: B --- 170. The hydride used in airships in the past was: A. hydrogen B. helium C. ammonia D. methane Correct Answer: A --- 171. The test for purity of hydrogen is that it burns with: A. pop sound B. pale blue flame and no pop C. explosion D. yellow flame Correct Answer: B --- 172. The metal that reacts explosively even with cold water is: A. Ca B. Mg C. K D. Zn Correct Answer: C --- 173. Hydrogen is placed separately in the periodic table because it: A. shows properties of both Group 1 and Group 17 B. is a gas C. has atomic number 1 D. is very reactive Correct Answer: A --- 174. The hydride LiAlH₄ is an example of: A. saline hydride B. covalent hydride C. complex hydride D. metallic hydride Correct Answer: C --- 175. Hydrogen is used in the manufacture of: A. NH₃ B. CH₃OH C. HCl D. all of the above Correct Answer: D --- 176. The equation for Bosch process stage 1 is: A. C + H₂O → CO + H₂ B. CO + H₂O → CO₂ + H₂ C. CO₂ + NaOH → Na₂CO₃ + H₂O D. C + O₂ → CO₂ Correct Answer: A --- 177. The catalyst in stage 2 of Bosch process is usually: A. Fe₂O₃ promoted with Cr₂O₃ B. V₂O₅ C. Ni D. Pt Correct Answer: A --- 178. The final purification step in Bosch process uses: A. water B. alkaline pyrogallol C. NaOH or KOH solution D. CuSO₄ solution Correct Answer: C --- 179. Hydrogen is used in atomic hydrogen torch to produce temperature up to: A. 2000 °C B. 2800 °C C. 4000 °C D. 6000 °C Correct Answer: C --- 180. The pop sound is due to: A. rapid combustion of H₂ with oxygen present in the jar B. cooling of gas C. reduction of air D. expansion of water Correct Answer: A --- 181. Hydrogen is not used in filling balloons nowadays because it is: A. expensive B. highly flammable C. heavier than air D. reactive with rubber Correct Answer: B

*CONTINUETION LAST* 141. The pale blue flame of burning hydrogen becomes almost invisible in daylight because it: A. produces no soot B. has very low luminosity C. produces water only D. is very hot Correct Answer: B --- 142. Hydrogen is used to fill weather balloons because it: A. is the lightest gas B. is cheap C. does not react with rubber D. burns slowly Correct Answer: A --- 143. In the laboratory, hydrogen is purified by passing it through: A. acidified KMnO₄ B. silver nitrate solution C. anhydrous calcium chloride D. sodium hydroxide pellets Correct Answer: B --- 144. The reaction 2H₂(g) + O₂(g) → 2H₂O(l) is highly: A. endothermic B. exothermic C. reversible D. slow Correct Answer: B --- 145. Which of the following hydrides is electron-deficient? A. CH₄ B. NH₃ C. H₂O D. B₂H₆ Correct Answer: D --- 146. Hydrogen acts as a reducing agent in the reaction: A. 2Na + H₂ → 2NaH B. CuO + H₂ → Cu + H₂O C. Cl₂ + H₂ → 2HCl D. N₂ + 3H₂ → 2NH₃ Correct Answer: B --- 147. The only hydride that is a liquid at room temperature among the following is: A. HF B. HCl C. HBr D. H₂O Correct Answer: D --- 148. The metal that will displace hydrogen from steam but not from cold water is: A. calcium B. zinc C. potassium D. sodium Correct Answer: B --- 149. In the reactivity series diagram in your book, hydrogen is placed directly between: A. lead and copper B. zinc and iron C. iron and lead D. copper and silver Correct Answer: A --- 150. The equation for the action of cold water on sodium is: A. 2Na + 2H₂O → 2NaOH + H₂ B. Na + H₂O → NaOH + ½H₂ C. 2Na + H₂O → Na₂O + H₂ D. Na + 2H₂O → Na(OH)₂ + H₂ Correct Answer: A --- 151. When steam is passed over red-hot coke, the gas produced is: A. producer gas B. water gas C. coal gas D. synthesis gas Correct Answer: B --- 152. The catalyst used in the conversion of water gas to hydrogen in Bosch process is: A. Fe₂O₃ B. V₂O₅ C. Ni D. Pt Correct Answer: A --- 153. Hydrogen is preferred as a fuel in rockets because it has: A. highest calorific value per gram B. lowest density C. both A and B D. no residue Correct Answer: C --- 154. The hydride formed when hydrogen reacts with calcium is: A. CaH₂ B. CaH C. Ca₂H D. Ca(OH)₂ Correct Answer: A --- 155. Which of the following is NOT a use of hydrogen? A. Filling balloons B. Cutting and welding metals C. Manufacture of HCl D. Bleaching agent Correct Answer: D --- 156. Hydrogen differs from alkali metals because it is: A. diatomic B. non-metal C. has one electron in outer shell but forms H⁻ rarely in compounds D. all of the above Correct Answer: D --- 157. The volume of hydrogen (at s.t.p.) produced when 1.3 g of zinc reacts completely with excess dilute acid is (Zn = 65): A. 224 cm³ B. 448 cm³ C. 11.2 dm³ D. 22.4 dm³ Correct Answer: B (0.02 mol Zn → 0.02 mol H₂ → 448 cm³) --- 158. In the pop-sound test, the pop is loudest when hydrogen is: A. pure B. mixed with little air C. mixed with excess air D. wet Correct Answer: B --- 159. The drying agent that cannot be used for drying hydrogen is: A. CaCl₂ B. P₂O₅ C. Conc. H₂SO₄ D. NaOH pellets Correct Answer: D --- 160. The metal that forms an amphoteric oxide and reacts with NaOH to liberate hydrogen is: A. Zn B. Fe C. Mg D. Al Correct Answer: D (Most accepted answer: D — Al) --- 161. The reaction 3Fe(s) + 4H₂O(g) ⇌ Fe₃O₄(s) + 4H₂(g) is driven backwards by: A. passing hydrogen over hot Fe₃O₄ B. increasing temperature C. using cold iron D. reducing steam supply Correct Answer: A --- 162. The colourless gas that rekindles a glowing splint is: A. hydrogen B. oxygen C. nitrogen D. carbon dioxide Correct Answer: B --- 163. Hydrogen is used in the manufacture of margarine by: A. hydrogenation of oils B. oxidation of oils C. dehydration D. hydration Correct Answer: A --- 164. The isotope tritium is: A. stable B. radioactive C. non-existent D. most abundant Correct Answer: B --- 165.