THE UNKNOWN SOLUTION TEAM

127. Aluminium reacts with hot concentrated NaOH to liberate hydrogen because aluminium forms: A. aluminate ion B. oxide layer C. chloride D. sulphate Correct Answer: A --- 128. The equation Al + NaOH + H₂O → ? + H₂ shows the product: A. NaAlO₂ B. Na₃AlO₃ C. Na[Al(OH)₄] D. Al(OH)₃ Correct Answer: C --- 129. The metal that reacts with both cold water and dilute acids vigorously is: A. calcium B. magnesium C. zinc D. iron Correct Answer: A --- 130. The black residue in steam + iron experiment is: A. triiron tetraoxide B. iron(II) oxide C. iron(III) oxide D. iron(II,III) oxide Correct Answer: A (or D — both refer to Fe₃O₄) --- 131. Hydrogen can reduce all the following except: A. CuO B. Fe₂O₃ C. Na₂O D. ZnO Correct Answer: C --- 132. The hydride NH₃ is: A. ionic B. covalent C. metallic D. saline Correct Answer: B --- 133. The hydride CH₄ belongs to: A. saline hydrides B. covalent hydrides C. interstitial hydrides D. complex hydrides Correct Answer: B --- 134. Hydrogen is a very powerful reducing agent in metallurgy because it: A. removes oxygen from metal oxides B. adds oxygen C. forms alloys D. cools the metal Correct Answer: A --- 135. The test tube is inverted over the iron filings in steam experiment to: A. collect hydrogen B. prevent air entering C. heat the iron D. cool the steam Correct Answer: B --- 136. The colour of litmus when sodium reacts with water containing phenolphthalein becomes: A. pink B. blue C. colourless D. red Correct Answer: A --- 137. Hydrogen is not collected by downward displacement of air because it is: A. lighter than air B. heavier than air C. soluble in water D. explosive Correct Answer: A --- 138. The common name for D₂O is: A. light water B. heavy water C. hard water D. soft water Correct Answer: B --- 139. Tritium has mass number: A. 1 B. 2 C. 3 D. 4 Correct Answer: C --- 140. Hydrogen is used in the manufacture of: A. ammonia B. margarine C. methanol D. all of the above Correct Answer: D

*CONTINUETION* 101. The reaction of sodium with cold water is so violent that the apparatus must: A. be heated B. use only a small piece of sodium C. use hot water D. use dilute acid Correct Answer: B --- 102. When sodium reacts with cold water, the gas evolved: A. burns with a yellow flame B. relights a glowing splint C. gives a pop sound with a lighted splint D. turns lime water milky Correct Answer: C --- 103. The function of the trough full of water in the sodium + cold water method is to: A. cool the sodium B. collect hydrogen by downward delivery C. allow the sodium to sink and react safely D. dissolve the sodium hydroxide formed Correct Answer: C --- 104. In the steam + red-hot iron experiment, a constant flow of steam is maintained to: A. prevent reverse reaction B. increase temperature C. dissolve iron D. produce more heat Correct Answer: A --- 105. The forward reaction between iron and steam is favoured by: A. low temperature B. removing hydrogen C. adding more iron D. using cold iron Correct Answer: B --- 106. Hydrogen reduces heated copper(II) oxide to shiny: A. red copper B. black copper C. brown copper D. grey copper Correct Answer: A --- 107. Which of the following does NOT liberate hydrogen from dilute acids? A. Magnesium B. Zinc C. Iron D. Silver Correct Answer: D --- 108. Metals below hydrogen in the reactivity series: A. liberate hydrogen from water B. liberate hydrogen from steam C. do not liberate hydrogen from dilute acids D. are strong reducing agents Correct Answer: C --- 109. The hydrides formed by elements of Group 1 and 2 are generally: A. covalent B. ionic/saline C. metallic D. complex Correct Answer: B --- 110. Which hydride is used as a moderator in nuclear reactors? A. NH₃ B. H₂O C. D₂O D. CH₄ Correct Answer: C --- 111. The isotope of hydrogen used in making heavy water is: A. protium B. deuterium C. tritium D. hydrogen-4 Correct Answer: B --- 112. The mass numbers of the three isotopes of hydrogen are: A. 1, 2, 3 B. 1, 1, 2 C. 2, 3, 4 D. 1, 2, 4 Correct Answer: A --- 113. The most abundant isotope of hydrogen is: A. protium B. deuterium C. tritium D. all are equal Correct Answer: A --- 114. Hydrogen behaves as an oxidising agent when it reacts with: A. Na B. CuO C. Fe₃O₄ D. PbO Correct Answer: A --- 115. The industrial preparation of hydrogen by Bosch process involves: A. water gas + steam B. electrolysis of brine C. cracking of petroleum D. fermentation Correct Answer: A --- 116. Water gas is a mixture of: A. CO + H₂ B. CO₂ + H₂ C. CH₄ + H₂ D. CO + N₂ Correct Answer: A --- 117. In the Bosch process, the catalyst used is: A. iron(III) oxide B. vanadium(V) oxide C. platinum D. nickel Correct Answer: A --- 118. The final step in Bosch process removes: A. CO B. CO₂ C. H₂S D. N₂ Correct Answer: B --- 119. Hydrogen is used for hardening oils because it: A. adds to unsaturated bonds B. removes oxygen C. reduces fats D. oxidises fats Correct Answer: A --- 120. Oxy-hydrogen flame reaches a temperature of about: A. 1000 °C B. 1800 °C C. 2800 °C D. 3500 °C Correct Answer: C --- 121. Hydrogen is used as a rocket fuel because it: A. has high calorific value B. is very light C. burns quietly D. both A and B Correct Answer: D --- 122. The gas that burns with a pop sound is: A. oxygen B. hydrogen C. nitrogen D. carbon dioxide Correct Answer: B --- 123. A lighted splint is extinguished with a pop sound in pure hydrogen because: A. hydrogen supports combustion B. hydrogen burns explosively in limited oxygen C. hydrogen is denser D. hydrogen is wet Correct Answer: B --- 124. Hydrogen is dried using: A. concentrated H₂SO₄ B. CaCl₂ C. P₂O₅ D. all of the above Correct Answer: D --- 125. The reagent that removes carbon(IV) oxide from hydrogen in industrial preparation is: A. water B. NaOH solution C. CuSO₄ solution D. CaO Correct Answer: B --- 126. In the reactivity series shown in your book, hydrogen is placed just above: A. copper B. iron C. lead D. silver Correct Answer: A ---

The reaction Zn + 2H⁺ → Zn²⁺ + H₂ is an example of: A. oxidation B. reduction C. redox D. neutralization Correct Answer: C --- 27. Hydrogen is a very good reducing agent because it: A. has low density B. readily accepts electrons C. readily donates electrons D. is diatomic Correct Answer: C --- 28. The laboratory test to distinguish hydrogen from carbon monoxide is: A. burning with pop B. passing through lime water C. burning with pale blue flame only D. reducing CuO to Cu Correct Answer: C --- 29. Hydrogen is used in oxy-hydrogen flame for: A. welding B. filling balloons C. Haber process D. hydrogenation of coal Correct Answer: A --- 30. The hydride NaH is: A. saline hydride B. covalent hydride C. metallic hydride D. complex hydride Correct Answer: A --- 98. When sodium is wrapped in wire gauze and dropped in water, it is done to: A. prevent explosion B. collect more gas C. make it sink D. increase reaction rate Correct Answer: A --- 99. The metal that reacts most vigorously with cold water is: A. Ca B. Na C. K D. Mg Correct Answer: C (K > Na > Ca > Mg) --- 100. Hydrogen is not collected by downward displacement of air because it is: A. lighter than air B. heavier than air C. soluble in water D. explosive Correct Answer: A

*QUESTIONS ON HYDROGEN* --- 1. Hydrogen was named “water-former” by Lavoisier because it: A. is found in water B. produces water when burnt in air C. dissolves in water D. is lighter than water Correct Answer: B --- 2. Cavendish is regarded as the discoverer of hydrogen because he was the first to: A. prepare it in the pure state B. recognise it as an element C. show that it is flammable D. collect it over water Correct Answer: B --- 3. Hydrogen makes up approximately what percentage of the earth’s crust by mass? A. 0.01 % B. 1 % C. 15 % D. 50 % Correct Answer: B (≈ 0.9–1 % by mass) --- 4. The most common laboratory method of preparing hydrogen is the reaction of: A. sodium with cold water B. steam on red-hot iron C. zinc with dilute acid D. aluminium with NaOH Correct Answer: C --- 5. Dilute tetraoxosulphate(VI) acid is preferred to dilute HCl when preparing hydrogen from zinc because: A. HCl is volatile B. chloride ions may form complex C. sulphate ions are larger D. HCl is more expensive Correct Answer: A --- 6. A few drops of copper(II) tetraoxosulphate(VI) solution are added in Zn + acid method in order to: A. act as catalyst B. remove surface oxide on zinc C. prevent formation of hydrogen sulphide D. increase solubility of zinc Correct Answer: A --- 7. Hydrogen is collected over water in the zinc + acid method because hydrogen is: A. slightly soluble in water B. completely insoluble in water C. denser than water D. soluble in mercury Correct Answer: A --- 8. The very first jar of hydrogen collected is discarded because it: A. contains oxygen B. is mixed with air C. contains water vapour only D. is impure hydrogen Correct Answer: B --- 9. When a small piece of sodium is dropped in cold water containing red litmus, the litmus turns: A. colourless B. blue C. pink then colourless D. remains red Correct Answer: B --- 10. Sodium reacts with cold water to produce hydrogen and: A. NaOH B. Na₂O C. NaH D. Na₂CO₃ Correct Answer: A --- 11. The reaction of steam on red-hot iron is: A. irreversible B. reversible C. explosive D. endothermic only Correct Answer: B --- 12. The black residue left when iron reacts with steam is: A. FeO B. Fe₂O₃ C. Fe₃O₄ D. Fe(OH)₃ Correct Answer: C --- 13. The equation for the reversible reaction of iron and steam is: A. 3Fe + 4H₂O ⇌ Fe₃O₄ + 4H₂ B. Fe + H₂O → FeO + H₂ C. 2Fe + 3H₂O → Fe₂O₃ + 3H₂ D. Fe + 2H₂O → Fe(OH)₂ + H₂ Correct Answer: A --- 14. Which metal will NOT liberate hydrogen from cold water? A. K B. Na C. Ca D. Mg Correct Answer: D (Mg reacts extremely slowly with cold water) --- 15. Which metal reacts with steam but not with cold water? A. Ca B. Mg C. Na D. K Correct Answer: B --- 16. Hydrogen burns in air with a: A. pop sound B. pale blue flame C. yellow flame D. green flame Correct Answer: B --- 17. A mixture of hydrogen and air explodes when ignited because the reaction is: A. highly exothermic B. highly endothermic C. slow D. reversible Correct Answer: A --- 18. The “pop” sound test for hydrogen works because hydrogen: A. burns quietly B. combines explosively with oxygen in the splint C. reduces the splint D. supports combustion Correct Answer: B --- 19. Hydrogen is placed in the reactivity series between: A. Zn and Fe B. Cu and Ag C. Pb and Cu D. Fe and Pb Correct Answer: C (Order: …Pb → H → Cu → Ag) --- 20. Which of the following metals will NOT displace hydrogen from dilute acids? A. Zn B. Fe C. Cu D. Mg Correct Answer: C --- 21. Hydrogen reduces copper(II) oxide to: A. CuO B. Cu C. Cu₂O D. Cu(OH)₂ Correct Answer: B --- 22. Hydrogen is used in the Haber process because it: A. is cheap B. gives higher yield than CO C. is pure D. is obtained from natural gas Correct Answer: D --- 23. The isotope of hydrogen with mass number 2 is called: A. protium B. deuterium C. tritium D. hydrogen-3 Correct Answer: B --- 24. Heavy water is: A. H₂O B. D₂O C. T₂O D. HTO Correct Answer: B --- 25.

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