📌 Introduction: Why Hydrogen is Special in ICSE Class 9

Hydrogen is the first element in the periodic table and the lightest gas known to science. In the ICSE Class 9 Chemistry syllabus, Hydrogen is studied as the “First Group Element” because it shows unique dual nature — resembling both alkali metals (Group 1) and halogens (Group 17) . Understanding Hydrogen is crucial because it forms the basis for many chemical concepts you will study later, including redox reactions, industrial preparation methods like the Bosch process, and Haber’s process.

At 📚 Dhingra Classes Nashik, we have prepared this comprehensive guide with 75 solved MCQs, 15 short answer questions, and 12 long answer questions to help you master this chapter thoroughly. Whether you are preparing for your ICSE board exams or school tests, this article covers everything you need.

📞 Contact Dhingra Classes for personalized coaching on Chemistry and all ICSE subjects!

🎯 Part A: 75 Solved Multiple Choice Questions (MCQs) on Hydrogen

🔬 Section 1: Position of Hydrogen in the Periodic Table (MCQs 1-15)

Q1. Hydrogen is placed in which group of the periodic table?
(a) Group 17 (b) Group 1 (c) Group 2 (d) Group 18

✅ Answer: (b) Group 1
Explanation: Hydrogen is placed in Group 1 because it has one valence electron like alkali metals.

Q2. Hydrogen shows dual nature because it resembles:
(a) Alkali metals only (b) Halogens only (c) Both alkali metals and halogens (d) Noble gases

✅ Answer: (c) Both alkali metals and halogens
Explanation: Hydrogen resembles alkali metals (one valence electron, forms cation) and halogens (one electron short of stable configuration, forms anion) .

Q3. Which of the following is NOT a similarity between hydrogen and alkali metals?
(a) Both have one valence electron (b) Both form cations (c) Both form basic oxides (d) Both are reducing agents

✅ Answer: (c) Both form basic oxides
Explanation: Oxides of alkali metals are basic, while hydrogen oxide (water) is neutral.

Q4. Hydrogen is placed in which period of the periodic table?
(a) Period 1 (b) Period 2 (c) Period 3 (d) Period 0

✅ Answer: (a) Period 1
Explanation: Hydrogen has only one shell, so it belongs to Period 1.

Q5. The electronic configuration of hydrogen is:
(a) 1s² (b) 1s¹ (c) 2s¹ (d) 2s²

✅ Answer: (b) 1s¹
Explanation: Hydrogen has one electron in its 1s orbital.

Q6. Hydrogen resembles halogens in which respect?
(a) Forming cations (b) Having one electron less than stable configuration (c) Forming basic oxides (d) Being a metal

✅ Answer: (b) Having one electron less than stable configuration
Explanation: Halogens need one electron to complete their octet, just like hydrogen needs one electron to achieve helium configuration.

Q7. Which of the following statements about hydrogen is INCORRECT?
(a) Hydrogen is the lightest element (b) Hydrogen forms only ionic compounds (c) Hydrogen acts as a reducing agent (d) Hydrogen burns with a pop sound

✅ Answer: (b) Hydrogen forms only ionic compounds
Explanation: Hydrogen forms both ionic compounds (like NaH) and covalent compounds (like H₂O, HCl) .

Q8. Hydrogen differs from halogens because:
(a) Hydrogen has one valence electron (b) Hydrogen has only one shell (c) Hydrogen forms anions (d) Hydrogen is a gas

✅ Answer: (b) Hydrogen has only one shell
Explanation: Halogens have two or more shells, while hydrogen has only one shell.

Q9. Which property makes hydrogen similar to alkali metals?
(a) Electronegativity (b) Electropositive character (c) Formation of acidic oxides (d) High density

✅ Answer: (b) Electropositive character
Explanation: Like alkali metals, hydrogen can lose one electron to form a positive ion (H⁺) .

Q10. Hydrogen oxide is:
(a) Acidic (b) Basic (c) Neutral (d) Amphoteric

✅ Answer: (c) Neutral
Explanation: Water (H₂O) is a neutral oxide, unlike alkali metal oxides which are basic.

Q11. The valency of hydrogen in most compounds is:
(a) 2 (b) 1 (c) 0 (d) 3

✅ Answer: (b) 1
Explanation: Hydrogen has one valence electron and shows a valency of 1.

Q12. Which of the following elements is placed before hydrogen in the reactivity series?
(a) Copper (b) Zinc (c) None, hydrogen is compared with metals (d) Silver

✅ Answer: (c) None, hydrogen is compared with metals
Explanation: In the activity series, metals are arranged based on their ability to displace hydrogen from acids.

Q13. Hydrogen was discovered by:
(a) Lavoisier (b) Henry Cavendish (c) Robert Boyle (d) Dalton

✅ Answer: (b) Henry Cavendish
Explanation: Henry Cavendish discovered hydrogen in 1766 and called it “inflammable air” .

Q14. Hydrogen is called “inflammable air” because:
(a) It is a noble gas (b) It burns easily (c) It extinguishes fire (d) It is heavier than air

✅ Answer: (b) It burns easily
Explanation: Hydrogen is highly combustible and burns in air with a pale blue flame.

Q15. The atomic number of hydrogen is:
(a) 0 (b) 1 (c) 2 (d) 3

✅ Answer: (b) 1
Explanation: Hydrogen has one proton in its nucleus.

🧪 Section 2: Laboratory Preparation of Hydrogen (MCQs 16-30)

Q16. In the laboratory, hydrogen is prepared by the reaction of:
(a) Copper with dilute HCl (b) Zinc with dilute HCl (c) Sodium with water (d) Iron with cold water

✅ Answer: (b) Zinc with dilute HCl
Explanation: Granulated zinc reacts with dilute hydrochloric acid or dilute sulphuric acid to produce hydrogen.

Q17. The chemical equation for laboratory preparation of hydrogen using zinc and dilute sulphuric acid is:
(a) Zn + H₂SO₄ → ZnSO₄ + H₂ (b) Zn + 2HCl → ZnCl₂ + H₂ (c) Both (a) and (b) (d) Zn + H₂O → ZnO + H₂

✅ Answer: (c) Both (a) and (b)
Explanation: Zinc reacts with both dilute H₂SO₄ and dilute HCl to produce hydrogen.

Q18. Why is granulated zinc preferred over pure zinc for laboratory preparation of hydrogen?
(a) It is cheaper (b) It has larger surface area (c) It contains copper impurity that catalyzes the reaction (d) Both (b) and (c)

✅ Answer: (d) Both (b) and (c)
Explanation: Granulated zinc has a larger surface area and contains copper impurity which acts as a catalyst.

Q19. Hydrogen is collected in the laboratory by:
(a) Upward displacement of air (b) Downward displacement of air (c) Downward displacement of water (d) Over mercury

✅ Answer: (c) Downward displacement of water
Explanation: Hydrogen is insoluble in water and is collected by downward displacement of water.

Q20. Why is hydrogen NOT collected by downward displacement of air?
(a) It is heavier than air (b) It forms an explosive mixture with air (c) It reacts with air (d) It is soluble in air

✅ Answer: (b) It forms an explosive mixture with air
Explanation: Hydrogen forms an explosive mixture with air, so it is collected over water instead.

Q21. The apparatus used for laboratory preparation of hydrogen is:
(a) Round bottom flask (b) Woulfe’s bottle (c) Beaker (d) Conical flask

✅ Answer: (b) Woulfe’s bottle
Explanation: A Woulfe’s bottle with a thistle funnel is used for laboratory preparation of hydrogen.

Q22. Which acid is NOT used for preparation of hydrogen from zinc?
(a) Dilute HCl (b) Dilute H₂SO₄ (c) Nitric acid (d) Both (c) and hot concentrated H₂SO₄

✅ Answer: (d) Both (c) and hot concentrated H₂SO₄
Explanation: Nitric acid is a strong oxidizing agent, and hot concentrated H₂SO₄ produces SO₂ instead of hydrogen.

Q23. Before collecting hydrogen, the gas should be tested by:
(a) Smell (b) Litmus paper (c) Burning splinter (pop test) (d) Lime water

✅ Answer: (c) Burning splinter (pop test)
Explanation: Hydrogen burns with a pop sound when a burning splinter is brought near it.

Q24. The impurities present in hydrogen prepared in the laboratory include:
(a) H₂S and SO₂ (b) PH₃ and AsH₃ (c) CO₂ and water vapour (d) All of the above

✅ Answer: (d) All of the above
Explanation: Impurities include H₂S, SO₂, PH₃, AsH₃, CO₂, and water vapour.

Q25. To remove H₂S impurity from hydrogen, the gas is passed through:
(a) Silver nitrate solution (b) Lead nitrate solution (c) Caustic potash (d) Anhydrous calcium chloride

✅ Answer: (b) Lead nitrate solution
Explanation: Lead nitrate solution absorbs H₂S.

Q26. To remove moisture from hydrogen gas, it is passed through:
(a) Lead nitrate (b) Silver nitrate (c) Anhydrous calcium chloride (d) KOH solution

✅ Answer: (c) Anhydrous calcium chloride
Explanation: Anhydrous calcium chloride or P₂O₅ is used to dry hydrogen gas.

Q27. Which metal cannot be used for preparation of hydrogen from dilute acids?
(a) Zinc (b) Magnesium (c) Copper (d) Iron

✅ Answer: (c) Copper
Explanation: Copper is below hydrogen in the reactivity series and cannot displace hydrogen.

Q28. Lead cannot be used for preparation of hydrogen from dilute H₂SO₄ because:
(a) It is too reactive (b) It forms an insoluble coating of lead sulphate (c) It reacts explosively (d) It is a non-metal

✅ Answer: (b) It forms an insoluble coating of lead sulphate
Explanation: Lead sulphate is insoluble and prevents further reaction.

Q29. Which of the following metals reacts with both acids and alkalies to produce hydrogen?
(a) Copper (b) Zinc (c) Silver (d) Gold

✅ Answer: (b) Zinc
Explanation: Zinc and aluminium are amphoteric and react with both acids and alkalies.

Q30. Zinc reacts with sodium hydroxide to produce:
(a) Zinc hydroxide (b) Sodium zincate (c) Zinc oxide (d) Zinc chloride

✅ Answer: (b) Sodium zincate
Explanation: Zn + 2NaOH → Na₂ZnO₂ + H₂ (Sodium zincate) .

⚗️ Section 3: Industrial Preparation of Hydrogen (MCQs 31-45)

Q31. The industrial method for preparation of hydrogen from water gas is called:
(a) Haber’s process (b) Bosch process (c) Contact process (d) Ostwald process

✅ Answer: (b) Bosch process
Explanation: The Bosch process involves passing steam over red-hot coke to produce water gas, then converting CO to CO₂.

Q32. The catalyst used in the Bosch process is:
(a) Nickel (b) Iron oxide (Fe₂O₃) (c) Vanadium pentoxide (d) Platinum

✅ Answer: (b) Iron oxide (Fe₂O₃)
Explanation: Ferric oxide (Fe₂O₃) is used as a catalyst in the Bosch process.

Q33. Water gas is a mixture of:
(a) H₂ and O₂ (b) H₂ and CO (c) H₂ and N₂ (d) H₂ and CO₂

✅ Answer: (b) H₂ and CO
Explanation: Water gas is a mixture of hydrogen and carbon monoxide.

Q34. In the Bosch process, carbon monoxide is removed by:
(a) Passing through water under pressure (b) Passing through ammoniacal cuprous chloride (c) Both (a) and (b) (d) Condensation

✅ Answer: (c) Both (a) and (b)
Explanation: CO is removed by dissolving in water under pressure or by passing through ammoniacal cuprous chloride.

Q35. Electrolysis of acidulated water produces hydrogen at:
(a) Anode (b) Cathode (c) Both electrodes (d) Neither electrode

✅ Answer: (b) Cathode
Explanation: Hydrogen is liberated at the cathode (negative electrode) during electrolysis.

Q36. The electrolyte used in electrolysis of water is:
(a) Pure water (b) Acidulated water (c) Sugar solution (d) Alcohol

✅ Answer: (b) Acidulated water
Explanation: Dilute H₂SO₄ is added to water to make it conducting.

Q37. In the Bosch process, steam is passed over:
(a) Red-hot iron (b) White-hot coke (c) Zinc (d) Magnesium

✅ Answer: (b) White-hot coke
Explanation: Steam is passed over white-hot coke at about 1000°C.

Q38. The optimum pressure in the Bosch process is:
(a) 1 atm (b) 200 atm (c) 10 atm (d) 50 atm

✅ Answer: (b) 200 atm
Explanation: The Bosch process operates at about 200 atmospheres pressure.

Q39. Hydrogen obtained from natural gas is called:
(a) Water gas (b) Reformate (c) Producer gas (d) Coal gas

✅ Answer: (b) Reformate
Explanation: Hydrogen from natural gas reforming is called reformate.

Q40. Which of the following can be used as a source of hydrogen?
(a) Water (b) Natural gas (c) Biomass (d) All of the above

✅ Answer: (d) All of the above
Explanation: Hydrogen can be obtained from water, natural gas, and biomass.

Q41. The reaction C + H₂O → CO + H₂ is:
(a) Exothermic (b) Endothermic (c) Neutral (d) Reversible

✅ Answer: (b) Endothermic
Explanation: This reaction requires heat and is endothermic.

Q42. In the Bosch process, after the shift reaction, CO₂ is removed by:
(a) Filtration (b) Dissolving in water under pressure (c) Evaporation (d) Distillation

✅ Answer: (b) Dissolving in water under pressure
Explanation: CO₂ is dissolved in water under pressure and removed.

Q43. Which process is used for large-scale production of hydrogen?
(a) Laboratory preparation (b) Bosch process (c) Electrolysis of brine (d) Both (b) and (c)

✅ Answer: (d) Both (b) and (c)
Explanation: Bosch process and electrolysis are used for industrial production.

Q44. Hydrogen from electrolysis of brine is obtained at:
(a) Anode (b) Cathode (c) Both (d) None

✅ Answer: (b) Cathode
Explanation: Hydrogen is produced at the cathode during electrolysis of brine.

Q45. The reaction 2H₂O → 2H₂ + O₂ represents:
(a) Combination (b) Decomposition (c) Displacement (d) Double displacement

✅ Answer: (b) Decomposition
Explanation: Water is decomposed into hydrogen and oxygen by electrolysis.

🔥 Section 4: Properties and Reactions of Hydrogen (MCQs 46-60)

Q46. Hydrogen burns in oxygen to form:
(a) Hydrogen peroxide (b) Water (c) Ozone (d) Hydrogen oxide

✅ Answer: (b) Water
Explanation: 2H₂ + O₂ → 2H₂O.

Q47. The flame of burning hydrogen is:
(a) Yellow (b) Pale blue (c) Green (d) Red

✅ Answer: (b) Pale blue
Explanation: Pure hydrogen burns with a pale blue flame.

Q48. Hydrogen acts as a reducing agent because it:
(a) Adds oxygen (b) Removes oxygen (c) Adds hydrogen (d) Both (b) and (c)

✅ Answer: (d) Both (b) and (c)
Explanation: Hydrogen removes oxygen from metal oxides and adds hydrogen to other substances.

Q49. When hydrogen is passed over heated copper oxide, the products are:
(a) Copper and water (b) Copper hydroxide (c) Copper and hydrogen peroxide (d) No reaction

✅ Answer: (a) Copper and water
Explanation: CuO + H₂ → Cu + H₂O (Reduction) .

Q50. The color change observed when hydrogen reduces copper oxide is:
(a) Red to black (b) Black to reddish-brown (c) White to blue (d) Green to yellow

✅ Answer: (b) Black to reddish-brown
Explanation: Black CuO changes to reddish-brown Cu.

Q51. Hydrogen reacts with chlorine in diffused sunlight to form:
(a) Hydrogen chloride (b) Hydrogen peroxide (c) Water (d) Chlorine dioxide

✅ Answer: (a) Hydrogen chloride
Explanation: H₂ + Cl₂ → 2HCl (in diffused sunlight) .

Q52. The reaction between hydrogen and chlorine in direct sunlight is:
(a) Slow (b) Explosive (c) No reaction (d) Reversible

✅ Answer: (b) Explosive
Explanation: In direct sunlight, the reaction is explosive.

Q53. Hydrogen reacts with nitrogen to form:
(a) Nitric acid (b) Ammonia (c) Nitrogen dioxide (d) Hydrazine

✅ Answer: (b) Ammonia
Explanation: N₂ + 3H₂ ⇌ 2NH₃ (Haber’s process) .

Q54. The catalyst used in Haber’s process is:
(a) Iron (b) Nickel (c) Platinum (d) Palladium

✅ Answer: (a) Iron
Explanation: Iron with molybdenum promoter is used in Haber’s process.

Q55. Hydrogen reacts with sulphur to form:
(a) Sulphuric acid (b) Hydrogen sulphide (c) Sulphur dioxide (d) Sulphur trioxide

✅ Answer: (b) Hydrogen sulphide
Explanation: H₂ + S → H₂S.

Q56. The process of adding hydrogen to unsaturated oils is called:
(a) Oxidation (b) Hydrogenation (c) Reduction (d) Saturation

✅ Answer: (b) Hydrogenation
Explanation: Hydrogenation converts unsaturated oils to saturated fats using nickel catalyst.

Q57. The gas liberated when hydrogen reacts with sodium is:
(a) Sodium oxide (b) Sodium hydride (c) Sodium hydroxide (d) No reaction

✅ Answer: (b) Sodium hydride
Explanation: 2Na + H₂ → 2NaH (Sodium hydride) .

Q58. The ability of metals like palladium to absorb hydrogen is called:
(a) Adsorption (b) Absorption (c) Occlusion (d) Diffusion

✅ Answer: (c) Occlusion
Explanation: Occlusion is the adsorption of gases on the surface of finely divided metals.

Q59. Hydrogen is sparingly soluble in water. This means it is:
(a) Highly soluble (b) Moderately soluble (c) Slightly soluble (d) Insoluble

✅ Answer: (c) Slightly soluble
Explanation: Sparingly soluble means slightly soluble.

Q60. The density of hydrogen at STP is approximately:
(a) 1.0 g/L (b) 0.09 g/L (c) 0.5 g/L (d) 2.0 g/L

✅ Answer: (b) 0.09 g/L
Explanation: Hydrogen has a density of 0.09 g/L at STP.

💡 Section 5: Uses and Applications of Hydrogen (MCQs 61-75)

Q61. Hydrogen is used in weather balloons because:
(a) It is heavy (b) It is lighter than air (c) It is non-flammable (d) It is soluble in water

✅ Answer: (b) It is lighter than air
Explanation: Hydrogen is the lightest gas, providing buoyancy.

Q62. Why is hydrogen NOT used in modern airships?
(a) It is too expensive (b) It is highly inflammable (c) It is heavier than air (d) It is toxic

✅ Answer: (b) It is highly inflammable
Explanation: Hydrogen is highly explosive when mixed with air.

Q63. Hydrogen is used in the manufacture of:
(a) Ammonia (b) Methanol (c) Hydrogenated oils (d) All of the above

✅ Answer: (d) All of the above
Explanation: Hydrogen is used in Haber’s process for ammonia, methanol production, and hydrogenation of oils.

Q64. The oxy-hydrogen flame is used for:
(a) Cooking (b) Welding and cutting metals (c) Lighting (d) Heating water

✅ Answer: (b) Welding and cutting metals
Explanation: The oxy-hydrogen flame produces very high temperature for welding.

Q65. Hydrogen is used as a fuel in:
(a) Cars (b) Rockets (c) Airplanes (d) Trains

✅ Answer: (b) Rockets
Explanation: Liquid hydrogen is used as rocket fuel.

Q66. In the food industry, hydrogen is used for:
(a) Cooking (b) Hydrogenation of oils (c) Preservation (d) Flavoring

✅ Answer: (b) Hydrogenation of oils
Explanation: Hydrogenation converts liquid oils to solid fats (vanaspati ghee).

Q67. Hydrogen is used in fuel cells to produce:
(a) Heat only (b) Electricity (c) Light (d) Sound

✅ Answer: (b) Electricity
Explanation: Fuel cells convert hydrogen and oxygen into electricity.

Q68. The “pop test” is used to identify:
(a) Oxygen (b) Hydrogen (c) Carbon dioxide (d) Nitrogen

✅ Answer: (b) Hydrogen
Explanation: Hydrogen burns with a characteristic pop sound.

Q69. Hydrogen is used in the production of:
(a) Vegetable ghee (b) Ammonia (c) Hydrochloric acid (d) All of the above

✅ Answer: (d) All of the above
Explanation: Hydrogen is a key raw material for many industrial products.

Q70. A candle brought near the mouth of a hydrogen-filled jar:
(a) Extinguishes (b) Burns brighter (c) Produces pop sound (d) Explodes

✅ Answer: (c) Produces pop sound
Explanation: Hydrogen burns with a pop at the mouth of the jar.

Q71. When a burning candle is pushed inside a hydrogen-filled jar:
(a) It burns brighter (b) It extinguishes (c) It produces pop sound (d) It explodes

✅ Answer: (b) It extinguishes
Explanation: Hydrogen is a non-supporter of combustion, so the candle extinguishes.

Q72. Hydrogen is preferred over helium for some applications because:
(a) It is cheaper (b) It is lighter (c) It is non-flammable (d) It is denser

✅ Answer: (b) It is lighter
Explanation: Hydrogen is lighter than helium, providing more lift.

Q73. The product of complete combustion of hydrogen is:
(a) Hydrogen peroxide (b) Water (c) Ozone (d) Hydrogen oxide

✅ Answer: (b) Water
Explanation: Complete combustion of hydrogen produces water only.

Q74. Hydrogen is used in the petroleum industry for:
(a) Cracking (b) Hydrocracking (c) Desulfurization (d) All of the above

✅ Answer: (d) All of the above
Explanation: Hydrogen is used in various petroleum refining processes.

Q75. The main advantage of hydrogen as a fuel is:
(a) It is cheap (b) It produces no pollutants (c) It is easy to store (d) It is abundant

✅ Answer: (b) It produces no pollutants
Explanation: Hydrogen produces only water on combustion, making it clean fuel.

✍️ Part B: 15 Solved Short Answer Questions on Hydrogen

Q1. Why is hydrogen placed in Group 1 of the periodic table?

✅ Answer: Hydrogen is placed in Group 1 because it has one valence electron, similar to alkali metals. It shows electropositive character and can lose one electron to form H⁺ ion, just like alkali metals form M⁺ ions.

Q2. Why does hydrogen show dual nature?

✅ Answer: Hydrogen resembles alkali metals of Group 1 (one valence electron, forms cation, reducing agent) and halogens of Group 17 (one electron short of stable configuration, forms anion, diatomic gas). This dual behavior makes hydrogen unique.

Q3. Write the balanced chemical equation for laboratory preparation of hydrogen.

✅ Answer: Zn + H₂SO₄ (dil.) → ZnSO₄ + H₂
Or: Zn + 2HCl (dil.) → ZnCl₂ + H₂.

Q4. Why is granulated zinc preferred over pure zinc?

✅ Answer: Granulated zinc has a larger surface area and contains copper impurity that acts as a catalyst, increasing the reaction rate.

Q5. Why is hydrogen collected by downward displacement of water?

✅ Answer: Hydrogen is insoluble in water and lighter than air. Since it forms an explosive mixture with air, it is collected by downward displacement of water.

Q6. What is the pop test for hydrogen?

✅ Answer: When a burning splinter is brought near hydrogen gas, it burns with a characteristic pop sound. This confirms the presence of hydrogen.

Q7. Why is nitric acid not used for preparation of hydrogen?

✅ Answer: Nitric acid is a strong oxidizing agent. It oxidizes the hydrogen produced to water, defeating the purpose of the reaction.

Q8. Name the impurities in laboratory-prepared hydrogen and how they are removed.

✅ Answer: Impurities: H₂S, SO₂, PH₃, AsH₃, CO₂, water vapour.
Removal: Lead nitrate (H₂S), Silver nitrate (PH₃, AsH₃), Caustic potash (SO₂, CO₂), Anhydrous CaCl₂ (moisture).

Q9. What is water gas?

✅ Answer: Water gas is a mixture of carbon monoxide (CO) and hydrogen (H₂). It is produced by passing steam over white-hot coke: C + H₂O → CO + H₂.

Q10. Explain the Bosch process for industrial preparation of hydrogen.

✅ Answer: In the Bosch process:
Step 1: Steam is passed over white-hot coke → Water gas (CO + H₂)
Step 2: CO + H₂O → CO₂ + H₂ (using Fe₂O₃ catalyst)
Step 3: CO₂ is removed by dissolving in water under pressure.

Q11. What is hydrogenation?

✅ Answer: Hydrogenation is the addition of hydrogen to unsaturated compounds in the presence of nickel catalyst to form saturated compounds. Example: Vegetable oils → Vanaspati ghee.

Q12. Why does a candle extinguish when pushed inside a hydrogen-filled jar?

✅ Answer: Hydrogen is a non-supporter of combustion. It does not allow substances to burn in it, so the candle extinguishes.

Q13. Give two tests to prove that hydrogen is lighter than air.

✅ Answer: (1) Soap bubble test: Hydrogen-filled soap bubbles rise in air. (2) Balloon test: Hydrogen-filled balloons rise.

Q14. What is occlusion?

✅ Answer: Occlusion is the adsorption of gases at the surface of finely divided metals. Palladium, platinum, and nickel readily occlude hydrogen gas.

Q15. Write the equation for the reaction between hydrogen and chlorine.

✅ Answer: H₂ + Cl₂ → 2HCl (in diffused sunlight)
In direct sunlight, the reaction is explosive.

📖 Part C: 12 Solved Long Answer Questions on Hydrogen

Q1. Explain the position of hydrogen in the periodic table with reference to its similarities with alkali metals and halogens.

✅ Answer:
Hydrogen is placed in Group 1 and Period 1 of the periodic table. It shows dual nature:

Similarities with Alkali Metals:

• Both have one valence electron

• Both form cations (H⁺, Na⁺)

• Both are reducing agents

• Both burn in oxygen

Similarities with Halogens:

• Both need one electron to achieve stable configuration

• Both form anions (H⁻, Cl⁻)

• Both have valency 1

• Both are diatomic (H₂, Cl₂)

Differences:

• Alkali metal oxides are basic; H₂O is neutral

• Halogens have multiple shells; hydrogen has one shell

This dual character makes hydrogen’s position unique in the periodic table.

Q2. Describe the laboratory preparation of hydrogen with a labeled diagram and precautions.

✅ Answer:
Apparatus: Woulfe’s bottle, thistle funnel, delivery tube, pneumatic trough.

Materials: Granulated zinc, dilute HCl or dilute H₂SO₄.

Reaction: Zn + 2HCl → ZnCl₂ + H₂

Procedure:

1. Place granulated zinc in Woulfe’s bottle

2. Pour dilute acid through thistle funnel

3. Collect hydrogen by downward displacement of water

Precautions:

• Apparatus should be air-tight

• No naked flame nearby

• Allow all air to escape before collecting

• Thistle funnel end should remain under acid.

Q3. Explain the industrial preparation of hydrogen by the Bosch process.

✅ Answer:
Bosch Process:

Step 1 — Water Gas Formation:
Steam is passed over white-hot coke at 1000°C:
C + H₂O → CO + H₂

Step 2 — Shift Reaction:
CO + H₂O → CO₂ + H₂ (using Fe₂O₃ catalyst at 400°C)

Step 3 — CO₂ Removal:
Carbon dioxide is dissolved in water under pressure and removed.

Step 4 — Purification:
Final purification by passing through ammoniacal cuprous chloride to remove traces of CO.

Q4. Explain the reducing property of hydrogen with examples.

✅ Answer:
Hydrogen acts as a reducing agent because it:

• Removes oxygen from metal oxides

• Adds hydrogen to other substances

Examples:

1. CuO + H₂ → Cu + H₂O (Black CuO → reddish-brown Cu)

2. PbO + H₂ → Pb + H₂O

3. Fe₃O₄ + 4H₂ → 3Fe + 4H₂O

4. Hydrogenation of oils: Vegetable oil + H₂ → Vanaspati (Ni catalyst)

In these reactions, hydrogen is oxidized while the metal oxide is reduced.

Q5. Compare hydrogen with halogens and alkali metals.

✅ Answer:

Hydrogen shows intermediate properties, resembling both groups.

Q6. What are the uses of hydrogen? Explain any five.

✅ Answer:

1. Manufacture of Ammonia: Haber’s process (N₂ + 3H₂ → 2NH₃)

2. Hydrogenation of Oils: Vegetable oils → Vanaspati ghee

3. Oxy-hydrogen Flame: Used for welding and cutting metals (high temperature)

4. Rocket Fuel: Liquid hydrogen as fuel in rockets

5. Fuel Cells: Produces electricity from H₂ and O₂

6. Weather Balloons: Being lightest gas.

Q7. Explain the reaction of hydrogen with non-metals.

✅ Answer:
With Oxygen: 2H₂ + O₂ → 2H₂O (pale blue flame, pop sound)
With Chlorine: H₂ + Cl₂ → 2HCl (diffused sunlight)
With Nitrogen: N₂ + 3H₂ ⇌ 2NH₃ (Haber’s process, Fe catalyst)
With Sulphur: H₂ + S → H₂S (hydrogen sulphide)

These reactions show hydrogen’s ability to form covalent compounds with non-metals.

Q8. Why are safety precautions essential during hydrogen preparation?

✅ Answer:
Hydrogen is highly inflammable and forms explosive mixture with air (4-75% hydrogen).

Precautions:

1. Apparatus must be air-tight

2. No naked flame near apparatus

3. Allow all air to escape before collecting gas

4. Use proper ventilation

5. Never use sodium or potassium (violent reaction)

6. Test gas with pop sound before collection.

Q9. Explain how hydrogen is prepared from water.

✅ Answer:
Method 1 — Active Metals:
2Na + 2H₂O → 2NaOH + H₂ (cold water, violent)
Ca + 2H₂O → Ca(OH)₂ + H₂ (cold water)
Mg + H₂O → MgO + H₂ (hot water)
3Fe + 4H₂O ⇌ Fe₃O₄ + 4H₂ (steam, reversible)

Method 2 — Electrolysis:
Acidulated water is electrolyzed:
2H₂O → 2H₂ + O₂
Hydrogen is collected at cathode.

Q10. Describe the properties of hydrogen.

✅ Answer:
Physical Properties:

• Colourless, odourless, tasteless gas

• Lightest gas (density 0.09 g/L)

• Sparingly soluble in water

• Liquefies at -253°C

Chemical Properties:

• Combustion: 2H₂ + O₂ → 2H₂O (pale blue flame)

• Reducing agent: CuO + H₂ → Cu + H₂O

• Reaction with non-metals: Forms HCl, NH₃, H₂S

• Reaction with metals: Forms hydrides (NaH)

• Hydrogenation: Addition to unsaturated compounds.

Q11. What are isotopes of hydrogen? Explain.

✅ Answer:
Hydrogen has three isotopes:

1. Protium (¹H): Most abundant, 0 neutrons

2. Deuterium (²H or D): 1 neutron, heavy hydrogen

3. Tritium (³H or T): 2 neutrons, radioactive

All have 1 proton but different mass numbers. They have same chemical properties but different physical properties.

Q12. Explain why hydrogen is called the fuel of the future.

✅ Answer:
Hydrogen is considered fuel of the future because:

1. Clean fuel: Produces only water on combustion

2. High energy content: Highest energy per unit mass

3. Renewable: Can be produced from water

4. No greenhouse gases: Zero carbon emissions

5. Fuel cells: Efficient electricity generation

Challenges: Storage, transportation, and production cost.

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