Q1. Which of the following is the best method for the large-scale preparation of dihydrogen?
A) Electrolysis of water
B) Lane’s process
C) Bosch process
D) Wurtz reaction
Answer: C) Bosch process
Explanation: The Bosch process is widely used for the large-scale industrial production of hydrogen. It involves the reaction of water vapor with hot carbon (usually coke) to produce hydrogen and carbon monoxide, followed by the water-gas shift reaction to increase the hydrogen yield.
Q2. What is the main impurity found in dihydrogen obtained by the electrolysis of water?
A) Carbon dioxide
B) Nitrogen
C) Oxygen
D) Sulphur dioxide
Answer: C) Oxygen
Explanation: During the electrolysis of water, hydrogen is produced at the cathode, while oxygen is released at the anode. Some oxygen may remain as an impurity in the dihydrogen produced, which needs to be purified before use.
Q3. The reaction of sodium with cold water produces which gas?
A) Oxygen
B) Hydrogen
C) Carbon dioxide
D) Nitrogen
Answer: B) Hydrogen
Explanation: When sodium reacts with cold water, sodium hydroxide (NaOH) and hydrogen gas (H₂) are formed. This is a typical method for the laboratory preparation of hydrogen using alkali metals.
Q4. Which of the following statements is NOT correct regarding hydrogen?
A) Hydrogen has the highest calorific value.
B) Hydrogen is a good conductor of electricity.
C) Hydrogen is highly flammable.
D) Hydrogen is the lightest element.
Answer: B) Hydrogen is a good conductor of electricity.
Explanation: Hydrogen, in its molecular form (H₂), is a poor conductor of electricity. It is a neutral molecule and does not have free electrons or ions to conduct an electric current.
Q5. The most abundant isotope of hydrogen in nature is:
A) Protium
B) Deuterium
C) Tritium
D) None of these
Answer: A) Protium
Explanation: Protium (¹H) is the most common isotope of hydrogen, comprising about 99.98% of the hydrogen found in nature. It has only one proton and no neutrons.
Q6. Hydrogen does not form which type of compound?
A) Ionic compounds
B) Covalent compounds
C) Interstitial compounds
D) Complex compounds
Answer: A) Ionic compounds
Explanation: Hydrogen typically forms covalent bonds by sharing electrons. However, it can form ionic bonds under certain conditions, such as with highly electronegative elements like halogens, but it does not commonly form typical ionic compounds.
Q7. Which of the following metals does not react with cold water to produce hydrogen gas?
A) Sodium
B) Magnesium
C) Calcium
D) Iron
Answer: D) Iron
Explanation: Iron does not react with cold water to produce hydrogen. It only reacts with steam at high temperatures, forming iron oxide and releasing hydrogen.
Q8. What is the oxidation state of hydrogen in NaH (sodium hydride)?
A) +1
B) -1
C) 0
D) +2
Answer: B) -1
Explanation: In metal hydrides like NaH, hydrogen has an oxidation state of -1. Sodium, being more electropositive, donates its electron to hydrogen.
Q9. Which of the following reactions is used in the preparation of hydrogen by the water-gas shift reaction?
A) CO + H₂O → CO₂ + H₂
B) CH₄ + H₂O → CO + 3H₂
C) H₂O + C → CO + H₂
D) H₂O₂ → H₂ + O₂
Answer: A) CO + H₂O → CO₂ + H₂
Explanation: The water-gas shift reaction is used to increase the yield of hydrogen by reacting carbon monoxide (CO) with water (H₂O) to produce carbon dioxide (CO₂) and hydrogen (H₂).
Q10. Which of the following reactions illustrates the reducing property of hydrogen?
A) H₂ + Cl₂ → 2HCl
B) H₂ + CuO → Cu + H₂O
C) H₂ + O₂ → H₂O
D) H₂ + N₂ → NH₃
Answer: B) H₂ + CuO → Cu + H₂O
Explanation: In this reaction, hydrogen reduces copper(II) oxide (CuO) to metallic copper (Cu), demonstrating its reducing property.
Q11. The reaction between zinc and dilute hydrochloric acid produces hydrogen. Which role does zinc play in this reaction?
A) Reducing agent
B) Oxidizing agent
C) Catalyst
D) Neutral compound
Answer: A) Reducing agent
Explanation: In the reaction between zinc and dilute HCl, zinc donates electrons to hydrogen ions, reducing them to hydrogen gas. Hence, zinc acts as a reducing agent.
Q12. The atomic number of hydrogen is 1. What does this indicate about its atomic structure?
A) One proton and no neutron
B) One proton and one neutron
C) One neutron and one electron
D) Two protons and one electron
Answer: A) One proton and no neutron
Explanation: The atomic number of hydrogen is 1, which means it has one proton and no neutrons in its most common isotope, protium (¹H).
Q13. Which of the following metals produces hydrogen gas when reacted with steam?
A) Sodium
B) Magnesium
C) Potassium
D) Lithium
Answer: B) Magnesium
Explanation: Magnesium reacts with steam to form magnesium oxide and hydrogen gas. Sodium and potassium react violently with cold water, while lithium reacts slowly with water.
Q14. Which property of hydrogen makes it useful as a fuel?
A) High atomic mass
B) Non-flammability
C) High calorific value
D) High density
Answer: C) High calorific value
Explanation: Hydrogen has the highest calorific value among known fuels, making it an excellent energy source when burned.
Q15. Hydrogen peroxide (H₂O₂) is a good example of hydrogen acting as:
A) An oxidizing agent
B) A reducing agent
C) Both A and B
D) Neither A nor B
Answer: C) Both A and B
Explanation: Hydrogen peroxide can act both as an oxidizing agent (e.g., in the presence of reducing substances) and as a reducing agent (e.g., in the presence of strong oxidizers like potassium permanganate).
Q16. Which of the following statements about hydrogen is true?
A) Hydrogen can act only as a reducing agent.
B) Hydrogen always exists as a diatomic molecule.
C) Hydrogen is the heaviest element.
D) Hydrogen has three naturally occurring isotopes.
Answer: D) Hydrogen has three naturally occurring isotopes.
Explanation: Hydrogen has three isotopes: protium (¹H), deuterium (²H), and tritium (³H). It can act as both a reducing and oxidizing agent, and it’s the lightest element, not the heaviest.
Q17. In which of the following reactions does hydrogen act as an oxidizing agent?
A) H₂ + Cl₂ → 2HCl
B) H₂ + O₂ → 2H₂O
C) H₂ + C → CH₄
D) H₂ + Na → NaH
Answer: D) H₂ + Na → NaH
Explanation: In this reaction, hydrogen accepts an electron from sodium, thus acting as an oxidizing agent.
Q18. What is the oxidation state of hydrogen in H₂O₂ (hydrogen peroxide)?
A) +1
B) -1
C) 0
D) -2
Answer: A) +1
Explanation: In hydrogen peroxide (H₂O₂), hydrogen has an oxidation state of +1, while oxygen has an oxidation state of -1.
Q19. Which of the following reactions is used to prepare heavy water (D₂O)?
A) Electrolysis of ordinary water
B) Reaction of hydrogen with oxygen
C) Reaction of deuterium with oxygen
D) None of the above
Answer: A) Electrolysis of ordinary water
Explanation: Heavy water (D₂O) is prepared by the electrolysis of ordinary water, where deuterium gets concentrated in the residual water as hydrogen escapes.
Q20. Which of the following compounds contains hydrogen in the negative oxidation state?
A) NH₃
B) H₂S
C) NaH
D) HCl
Answer: C) NaH
Explanation: In sodium hydride (NaH), hydrogen has an oxidation state of -1, as it gains an electron from sodium.
Q21. Which of the following substances can act as both a reducing agent and an oxidizing agent?
A) NaH
B) H₂
C) H₂O₂
D) HCl
Answer: C) H₂O₂
Explanation: Hydrogen peroxide (H₂O₂) can act both as an oxidizing agent and as a reducing agent, depending on the chemical environment.
Q22. The reaction of water gas (CO + H₂) with steam in the presence of a catalyst to form hydrogen is called:
A) Haber process
B) Bosch process
C) Lane’s process
D) Water-gas shift reaction
Answer: D) Water-gas shift reaction
Explanation: The water-gas shift reaction increases the yield of hydrogen by reacting water gas (CO + H₂) with steam, producing CO₂ and H₂.
Q23. Which of the following is not a property of hydrogen?
A) It has high energy content.
B) It is highly soluble in water.
C) It is the lightest gas.
D) It is non-toxic.
Answer: B) It is highly soluble in water.
Explanation: Hydrogen is only sparingly soluble in water, making this statement incorrect.
Q24. Hydrogen does not react with which of the following under normal conditions?
A) Oxygen
B) Nitrogen
C) Carbon
D) Noble gases
Answer: D) Noble gases
Explanation: Noble gases are chemically inert under normal conditions and do not react with hydrogen.
Q25. Which of the following isotopes of hydrogen is radioactive?
A) Protium
B) Deuterium
C) Tritium
D) All of the above
Answer: C) Tritium
Explanation: Tritium (³H) is radioactive, while protium (¹H) and deuterium (²H) are stable isotopes.
Q26. Hydrogen is collected over water because:
A) It is highly soluble in water
B) It is sparingly soluble in water
C) It reacts with water
D) It has a high density
Answer: B) It is sparingly soluble in water
Explanation: Hydrogen is collected over water because it is only sparingly soluble in water, meaning only a small amount dissolves, allowing the gas to be collected easily.
Q27. The bond dissociation energy of H-H bond in H₂ molecule is:
A) Low
B) Moderate
C) High
D) Zero
Answer: C) High
Explanation: The bond dissociation energy of H-H bond is high, as the bond between the two hydrogen atoms is strong due to its short bond length and high bond energy.
Q28. Hydrogen forms a diatomic molecule (H₂) because:
A) It forms ionic bonds.
B) It shares one electron with another hydrogen atom to complete its duplet.
C) It prefers to remain monatomic.
D) It forms a triple bond with another hydrogen atom.
Answer: B) It shares one electron with another hydrogen atom to complete its duplet.
Explanation: Hydrogen shares one electron with another hydrogen atom, forming a covalent bond and completing the duplet.
Q29. Hydrogen burns in air with a:
A) Blue flame
B) Yellow flame
C) Colorless flame
D) Red flame
Answer: C) Colorless flame
Explanation: Hydrogen burns with a pale blue or almost colorless flame in air, producing water as the only byproduct.
Q30. Hydrogen gas can reduce metal oxides to their respective metals at high temperatures. This property is due to its:
A) High reactivity
B) Reducing nature
C) Low atomic mass
D) High calorific value
Answer: B) Reducing nature
Explanation: Hydrogen is a good reducing agent and can reduce metal oxides like CuO to their respective metals at high temperatures.
Q31. Which of the following is not a correct method for preparing hydrogen in the laboratory?
A) Reaction of metals with acids
B) Reaction of alkali metals with cold water
C) Electrolysis of brine
D) Heating sodium with potassium
Answer: D) Heating sodium with potassium
Explanation: Heating sodium with potassium is not a method to prepare hydrogen. Hydrogen is commonly prepared by reacting metals with acids or electrolysis of brine.
Q32. Hydrogen is placed in the reactivity series:
A) Above sodium
B) Below iron
C) Between copper and lead
D) Between zinc and copper
Answer: D) Between zinc and copper
Explanation: In the reactivity series, hydrogen is placed between zinc and copper, meaning it is less reactive than zinc but more reactive than copper.
Q33. Which of the following pairs of elements does not form a hydride?
A) Sodium and hydrogen
B) Fluorine and hydrogen
C) Carbon and hydrogen
D) Helium and hydrogen
Answer: D) Helium and hydrogen
Explanation: Helium is a noble gas and does not form hydrides with hydrogen due to its inert nature.
Q34. Which property of hydrogen allows it to be used in the hydrogenation of oils?
A) Oxidizing nature
B) Reducing nature
C) High solubility in water
D) Inertness
Answer: B) Reducing nature
Explanation: Hydrogen acts as a reducing agent in the hydrogenation of unsaturated oils, converting them into saturated fats.
Q35. Hydrogen is used in fuel cells because:
A) It is easily available
B) It is a good reducing agent
C) It has high energy content
D) It produces carbon dioxide as a byproduct
Answer: C) It has high energy content
Explanation: Hydrogen has a high energy content and when used in fuel cells, it produces electricity with water as the only byproduct, making it a clean energy source.
Q36. The catalytic reduction of alkynes to alkenes using hydrogen is called:
A) Sabatier process
B) Wurtz reaction
C) Lindlar reduction
D) Friedel-Crafts reaction
Answer: C) Lindlar reduction
Explanation: Lindlar reduction involves the catalytic hydrogenation of alkynes to alkenes, using a poisoned catalyst to stop further reduction to alkanes.
Q37. Which of the following is not an isotope of hydrogen?
A) Protium
B) Deuterium
C) Tritium
D) Hydronium
Answer: D) Hydronium
Explanation: Hydronium (H₃O⁺) is not an isotope but rather a hydrated proton. Protium, deuterium, and tritium are the isotopes of hydrogen.
Q38. Hydrogen reacts explosively with which of the following elements?
A) Oxygen
B) Nitrogen
C) Fluorine
D) Neon
Answer: C) Fluorine
Explanation: Hydrogen reacts explosively with fluorine, forming hydrogen fluoride (HF), due to the highly reactive nature of fluorine.
Q39. Hydrogen is used in weather balloons because:
A) It is non-flammable
B) It is lighter than air
C) It is a good conductor of electricity
D) It dissolves in air
Answer: B) It is lighter than air
Explanation: Hydrogen is much lighter than air, which allows weather balloons filled with hydrogen to rise to great altitudes.
Q40. Hydrogen shows similarity in its chemical properties with which of the following groups?
A) Group 1 (alkali metals)
B) Group 2 (alkaline earth metals)
C) Group 16 (chalcogens)
D) Group 17 (halogens)
Answer: D) Group 17 (halogens)
Explanation: Hydrogen shows similarity to Group 17 elements (halogens) in its ability to form diatomic molecules (H₂ like Cl₂) and its tendency to gain one electron to form H⁻, like halogens forming X⁻ ions.
Q41. The reaction between zinc and sulfuric acid to produce hydrogen gas is an example of:
A) Neutralization
B) Redox reaction
C) Displacement reaction
D) Precipitation reaction
Answer: C) Displacement reaction
Explanation: In the reaction, zinc displaces hydrogen from sulfuric acid, producing hydrogen gas and zinc sulfate, making it a displacement reaction.
Q42. Which of the following hydrides is not a covalent hydride?
A) NH₃
B) H₂O
C) NaH
D) CH₄
Answer: C) NaH
Explanation: Sodium hydride (NaH) is an ionic hydride, not a covalent hydride. The others form covalent bonds with hydrogen.
Q43. The preparation of hydrogen by electrolysis involves the following half-reaction at the cathode:
A) 2H⁺ + 2e⁻ → H₂
B) O₂ + 4e⁻ → 2O²⁻
C) H₂O → 2H⁺ + ½O₂ + 2e⁻
D) 2OH⁻ → H₂O + ½O₂ + 2e⁻
Answer: A) 2H⁺ + 2e⁻ → H₂
Explanation: During electrolysis, at the cathode, hydrogen ions (H⁺) are reduced to form hydrogen gas.
Q44. Which of the following is true regarding hydrogen’s position in the periodic table?
A) It is placed only in Group 1.
B) It is placed only in Group 17.
C) It shows properties similar to both alkali metals and halogens.
D) It is placed at the center of the periodic table.
Answer: C) It shows properties similar to both alkali metals and halogens.
Explanation: Hydrogen shows similarity to alkali metals by losing an electron to form H⁺ and to halogens by gaining an electron to form H⁻.
Q45. Which of the following is an example of an interstitial hydride?
A) NaH
B) H₂O
C) TiHₓ
D) CH₄
Answer: C) TiHₓ
Explanation: Interstitial hydrides are formed when hydrogen occupies the interstices (voids) of metal lattices. Titanium hydride (TiHₓ) is an example.
Q46. The following gas is often used to detect leaks in pipelines because of its low molecular weight and high diffusion rate:
A) Oxygen
B) Helium
C) Hydrogen
D) Nitrogen
Answer: C) Hydrogen
Explanation: Hydrogen is used in detecting leaks due to its low molecular weight, which allows it to diffuse quickly through small gaps.
Q47. Which of the following compounds is an electron-deficient hydride?
A) B₂H₆
B) H₂S
C) NH₃
D) H₂O
Answer: A) B₂H₆
Explanation: Diborane (B₂H₆) is an electron-deficient compound because boron does not have enough electrons to form conventional two-electron bonds with hydrogen.
Q48. Which of the following is not a property of heavy water (D₂O)?
A) It has a higher boiling point than ordinary water.
B) It is used as a moderator in nuclear reactors.
C) It reacts more slowly than ordinary water.
D) It can be used as drinking water.
Answer: D) It can be used as drinking water.
Explanation: Heavy water is toxic if consumed in large quantities, and it is not suitable for drinking.
Q49. The dihydrogen molecule (H₂) has:
A) Ionic bonding
B) Polar covalent bonding
C) Non-polar covalent bonding
D) Metallic bonding
Answer: C) Non-polar covalent bonding
Explanation: The H₂ molecule has non-polar covalent bonding because both hydrogen atoms share electrons equally.
Q50. The oxidation state of hydrogen in hydrides of alkali metals is:
A) +1
B) -1
C) 0
D) +2
Answer: B) -1
Explanation: In metal hydrides like sodium hydride (NaH), hydrogen has an oxidation state of -1, as it gains an electron from the metal.
Q51. Which method is not suitable for the laboratory preparation of hydrogen?
A) Reaction of zinc with dilute sulfuric acid
B) Electrolysis of water
C) Reaction of aluminum with sodium hydroxide
D) Reaction of calcium with cold water
Answer: D) Reaction of calcium with cold water
Explanation: The reaction of calcium with cold water produces hydrogen, but it is too vigorous and exothermic, making it unsafe for laboratory preparation.
Q52. The oxidation state of hydrogen in hydrogen peroxide (H₂O₂) is:
A) 0
B) -1
C) +1
D) -2
Answer: C) +1
Explanation: In hydrogen peroxide, hydrogen has an oxidation state of +1, while oxygen has an oxidation state of -1.
Q53. Which of the following metal hydrides is ionic in nature?
A) CaH₂
B) NH₃
C) H₂O
D) PH₃
Answer: A) CaH₂
Explanation: Calcium hydride (CaH₂) is an ionic hydride because it consists of Ca²⁺ and H⁻ ions.
Q54. The hydrogen gas evolved in the reaction between zinc and hydrochloric acid is collected by:
A) Upward displacement of air
B) Downward displacement of water
C) Downward displacement of air
D) None of the above
Answer: B) Downward displacement of water
Explanation: Hydrogen is collected by downward displacement of water because it is insoluble in water and lighter than air.
Q55. The reaction of hydrogen with which of the following will produce ammonia?
A) Oxygen
B) Nitrogen
C) Chlorine
D) Sulfur
Answer: B) Nitrogen
Explanation: Hydrogen reacts with nitrogen under specific conditions (Haber process) to form ammonia (NH₃).
Q56. Which statement is true about hydrogen peroxide (H₂O₂)?
A) It is a strong reducing agent only.
B) It is a strong oxidizing agent only.
C) It can act as both an oxidizing and reducing agent.
D) It is always neutral in reactions.
Answer: C) It can act as both an oxidizing and reducing agent.
Explanation: Hydrogen peroxide can act as both an oxidizing and reducing agent, depending on the reactants.
Q57. The presence of deuterium in water molecules makes it:
A) More reactive than ordinary water
B) More stable than ordinary water
C) A weaker solvent than ordinary water
D) Less stable than ordinary water
Answer: B) More stable than ordinary water
Explanation: Heavy water (D₂O) is more stable than ordinary water (H₂O) because the bond between deuterium and oxygen is stronger than the bond between protium and oxygen.
Q58. Which of the following hydrides is the most stable?
A) LiH
B) NaH
C) KH
D) RbH
Answer: A) LiH
Explanation: Lithium hydride (LiH) is the most stable hydride among alkali metal hydrides because the smaller size of Li⁺ leads to stronger ionic bonds with H⁻.
Q59. Which of the following processes is used for the commercial production of hydrogen?
A) Reaction of zinc with sulfuric acid
B) Lane’s process
C) Electrolysis of brine
D) Haber process
Answer: B) Lane’s process
Explanation: Lane’s process is used commercially for the production of hydrogen by reacting steam with iron at high temperatures.
Q60. Which of the following has the highest bond dissociation enthalpy?
A) H₂
B) O₂
C) N₂
D) F₂
Answer: C) N₂
Explanation: Nitrogen (N₂) has the highest bond dissociation enthalpy due to its triple bond. However, H₂ also has a significantly high bond dissociation energy compared to many other diatomic molecules.
Q61. The chemical formula of heavy water is:
A) H₂O
B) D₂O
C) T₂O
D) DHO
Answer: B) D₂O
Explanation: Heavy water consists of deuterium (D) instead of protium (H), making its formula D₂O.
Q62. Which of the following is a use of hydrogen in the chemical industry?
A) Production of ammonia
B) As a refrigerant
C) Manufacture of nitric acid
D) Production of sulfuric acid
Answer: A) Production of ammonia
Explanation: Hydrogen is used in the Haber process for the production of ammonia, which is a key industrial application.
Q64. Hydrogen reacts with chlorine in the presence of sunlight to produce:
A) H₂O
B) HCl
C) Cl₂O
D) ClO₃⁻
Answer: B) HCl
Explanation: Hydrogen reacts explosively with chlorine in the presence of sunlight to form hydrogen chloride (HCl).
Q65. Which of the following metals does not liberate hydrogen from acids?
A) Zinc
B) Copper
C) Iron
D) Magnesium
Answer: B) Copper
Explanation: Copper does not liberate hydrogen from dilute acids because it is less reactive than hydrogen in the electrochemical series.
Q66. The property of hydrogen responsible for its reducing nature is:
A) Low ionization enthalpy
B) High electronegativity
C) Tendency to lose electrons
D) Ability to gain protons
Answer: C) Tendency to lose electrons
Explanation: Hydrogen acts as a reducing agent because it can lose electrons and reduce other substances.
Q67. The process used for the large-scale production of hydrogen by passing steam over red-hot iron is called:
A) Haber process
B) Bosch process
C) Lane’s process
D) Contact process
Answer: C) Lane’s process
Explanation: Lane’s process involves passing steam over red-hot iron to produce hydrogen gas and iron oxide.
Q68. Hydrogen can act as a reducing agent with:
A) Oxygen
B) Carbon dioxide
C) Nitrogen
D) All of the above
Answer: D) All of the above
Explanation: Hydrogen acts as a reducing agent with substances like oxygen, carbon dioxide, and nitrogen to form water, hydrocarbons, and ammonia, respectively.
Q69. The use of hydrogen in space rockets is due to its:
A) Low reactivity
B) High reactivity
C) Low energy content
D) High energy content
Answer: D) High energy content
Explanation: Hydrogen has a high energy content, making it an excellent fuel for space rockets where high energy is required.
Q70. In which of the following compounds does hydrogen exhibit a negative oxidation state?
A) H₂O
B) CH₄
C) H₂SO₄
D) H₂O₂
Answer: B) CH₄
Explanation: In methane (CH₄), hydrogen has an oxidation state of -1, as it forms a bond with a less electronegative element (carbon).
Q71. Which of the following statements is not true about hydrogen?
A) It has the highest calorific value of all known fuels.
B) It is a colorless and odorless gas.
C) It is highly soluble in water.
D) It is highly inflammable.
Answer: C) It is highly soluble in water.
Explanation: Hydrogen is only sparingly soluble in water, not highly soluble.
Q72. Which of the following is not a method of producing hydrogen gas?
A) Reaction of metals with acids
B) Electrolysis of water
C) Combustion of hydrocarbons
D) Reaction of metals with bases
Answer: C) Combustion of hydrocarbons
Explanation: The combustion of hydrocarbons produces carbon dioxide and water, not hydrogen gas.
Q73. Which of the following reactions does not involve the production of hydrogen gas?
A) Zn + H₂SO₄ → ZnSO₄ + H₂
B) Mg + HCl → MgCl₂ + H₂
C) Fe + H₂O → Fe₃O₄ + H₂
D) Cu + HCl → CuCl₂ + H₂
Answer: D) Cu + HCl → CuCl₂ + H₂
Explanation: Copper does not react with HCl to produce hydrogen because it is less reactive than hydrogen.
Q74. What is the major industrial use of hydrogen?
A) Production of water
B) Production of hydrocarbons
C) Production of ammonia
D) Production of hydrogen peroxide
Answer: C) Production of ammonia
Explanation: Hydrogen is mainly used industrially in the Haber process for the production of ammonia.
Q75. Which of the following is a feature of atomic hydrogen?
A) It is highly stable.
B) It exists only at very high temperatures.
C) It is used in the synthesis of D₂O.
D) It forms diatomic hydrogen immediately.
Answer: B) It exists only at very high temperatures.
Explanation: Atomic hydrogen is highly reactive and exists only at high temperatures before recombining into diatomic hydrogen.
Q76. When hydrogen gas is passed over heated copper oxide, it forms:
A) Copper and water
B) Copper and oxygen
C) Copper oxide and hydrogen peroxide
D) Copper chloride and water
Answer: A) Copper and water
Explanation: Hydrogen reduces copper oxide (CuO) to copper, forming water as a byproduct.
Q77. The oxidation state of hydrogen in metal hydrides such as NaH is:
A) +1
B) 0
C) -1
D) +2
Answer: C) -1
Explanation: In metal hydrides, hydrogen has an oxidation state of -1 as it gains an electron from the metal.
Q78. Which of the following statements is correct about hydrogen bonding in water?
A) It makes water less dense than ice.
B) It makes water molecules less associated.
C) It results in a high boiling point for water.
D) It makes water an ionic compound.
Answer: C) It results in a high boiling point for water.
Explanation: Hydrogen bonding leads to strong intermolecular forces in water, causing it to have a high boiling point compared to other similar-sized molecules.
Q79. Hydrogen combines with oxygen to form water, releasing a large amount of energy. This reaction is called:
A) Oxidation
B) Reduction
C) Combustion
D) Hydrogenation
Answer: C) Combustion
Explanation: When hydrogen combines with oxygen to form water, the process is a combustion reaction, releasing a large amount of energy.
Q80. The catalyst used in the preparation of hydrogen by the reaction of water gas with steam is:
A) Iron
B) Nickel
C) Platinum
D) Vanadium
Answer: B) Nickel
Explanation: Nickel is used as a catalyst in the water-gas shift reaction to increase hydrogen production.
Q81. Hydrogen reacts with metals to form:
A) Salts
B) Hydrides
C) Acids
D) Oxides
Answer: B) Hydrides
Explanation: Hydrogen reacts with metals to form metal hydrides like NaH and CaH₂.
Q82. The oxidation state of hydrogen in ammonia (NH₃) is:
A) +1
B) 0
C) -1
D) +2
Answer: A) +1
Explanation: In ammonia (NH₃), hydrogen has an oxidation state of +1 as it is bonded to a more electronegative element, nitrogen.
Q83. The most abundant isotope of hydrogen in nature is:
A) Protium
B) Deuterium
C) Tritium
D) None of the above
Answer: A) Protium
Explanation: Protium (¹H) is the most abundant isotope of hydrogen, making up over 99% of naturally occurring hydrogen.
Q84. In which of the following hydrides does hydrogen have the oxidation state of -1?
A) H₂O
B) HCl
C) NaH
D) CH₄
Answer: C) NaH
Explanation: In sodium hydride (NaH), hydrogen has an oxidation state of -1 because it gains an electron from sodium.
Q85. Which of the following reactions is used for the preparation of hydrogen gas?
A) Ca + H₂O → Ca(OH)₂ + H₂
B) NaOH + HCl → NaCl + H₂O
C) ZnO + H₂ → Zn + H₂O
D) CO + H₂O → CO₂ + H₂
Answer: D) CO + H₂O → CO₂ + H₂
Explanation: This is the water-gas shift reaction, used for hydrogen production, where carbon monoxide reacts with steam to form carbon dioxide and hydrogen.
Q86. Which of the following is not a property of hydrogen?
A) It is highly inflammable.
B) It is denser than air.
C) It has high diffusibility.
D) It has high energy content.
Answer: B) It is denser than air.
Explanation: Hydrogen is much less dense than air, making this statement incorrect.
Q87. The reaction of sodium with water produces:
A) Sodium oxide and hydrogen
B) Sodium hydroxide and hydrogen
C) Sodium chloride and hydrogen
D) Sodium peroxide and hydrogen
Answer: B) Sodium hydroxide and hydrogen
Explanation: Sodium reacts with water to form sodium hydroxide and hydrogen gas.
Q92. Hydrogen behaves as a metal in:
A) Solid state
B) Gaseous state
C) Liquid state
D) Plasma state
Answer: A) Solid state
Explanation: Under extreme pressure, hydrogen can exhibit metallic properties in its solid state.
Q93. Which of the following statements is correct about the reaction of hydrogen with alkali metals?
A) Hydrogen forms covalent bonds with alkali metals.
B) Hydrogen forms ionic hydrides with alkali metals.
C) Hydrogen forms hydrogen bonds with alkali metals.
D) Hydrogen forms metallic bonds with alkali metals.
Answer: B) Hydrogen forms ionic hydrides with alkali metals.
Explanation: Hydrogen forms ionic hydrides (e.g., NaH, LiH) with alkali metals, where hydrogen exists as a hydride ion (H⁻).
Q94. Which of the following statements is true about the reaction of hydrogen with oxygen?
A) It requires high temperature to proceed.
B) It is a slow process at room temperature.
C) It is highly exothermic.
D) It produces ozone.
Answer: C) It is highly exothermic.
Explanation: The reaction between hydrogen and oxygen is highly exothermic and releases a large amount of energy, forming water.
Q95. Which of the following is a feature of metallic hydrides?
A) They are good conductors of electricity.
B) They are molecular in nature.
C) They are ionic compounds.
D) They are formed by s-block elements only.
Answer: A) They are good conductors of electricity.
Explanation: Metallic hydrides, especially those formed by transition metals, can conduct electricity due to the presence of free electrons.
Q96. Which property of hydrogen is utilized in the hydrogenation of oils?
A) Reducing property
B) Oxidizing property
C) Acidity
D) Basicity
Answer: A) Reducing property
Explanation: In the hydrogenation of oils, hydrogen reduces the double bonds in unsaturated fats, converting them into saturated fats.
Q97. Hydrogen gas burns in air with a:
A) Blue flame
B) Green flame
C) Pale blue flame
D) Yellow flame
Answer: C) Pale blue flame
Explanation: Hydrogen burns in air with a pale blue flame, producing water vapor.
Q98. In which of the following reactions does hydrogen act as an oxidizing agent?
A) H₂ + O₂ → H₂O
B) H₂ + CO → CH₃OH
C) H₂ + N₂ → NH₃
D) H₂ + Na → NaH
Answer: D) H₂ + Na → NaH
Explanation: In this reaction, hydrogen accepts an electron from sodium and thus acts as an oxidizing agent.
Q99. The dissolution of hydrogen gas in metals is an example of:
A) Physical adsorption
B) Chemisorption
C) Interstitial solution
D) Sublimation
Answer: C) Interstitial solution
Explanation: Hydrogen atoms occupy interstitial sites in the metal lattice, forming an interstitial solution.
Q100. Which of the following is true about the isotopes of hydrogen?
A) All isotopes of hydrogen are radioactive.
B) Deuterium and tritium are stable isotopes.
C) Tritium is radioactive, while protium and deuterium are stable.
D) Only protium is radioactive.
Answer: C) Tritium is radioactive, while protium and deuterium are stable.
Explanation: Tritium (³H) is radioactive, whereas protium (¹H) and deuterium (²H) are stable isotopes of hydrogen.
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