Hydrogen and its Compounds (Practice Questions)

Hydrogen and its Compounds – Practice 40 MCQs

This section provides 40 multiple-choice questions covering key concepts from Hydrogen and its Compounds, essential for your NEET and JEE Main preparation. Each question has four options, with only one correct answer.

Section 1: Multiple Choice Questions (MCQs)

Instructions: Choose the single best answer for each question.

  1. Which of the following is true about the electronic configuration of hydrogen? A) It resembles alkali metals only. B) It resembles halogens only. C) It resembles both alkali metals and halogens. D) It is unique and resembles no other group.
  2. Which isotope of hydrogen is radioactive? A) Protium B) Deuterium C) Tritium D) All of the above
  3. The most abundant isotope of hydrogen is: A) Protium B) Deuterium C) Tritium D) Heavy hydrogen
  4. Heavy water is represented by the formula: A) H2O B) D2O C) T2O D) H2O2
  5. Which of the following metals reacts with hot concentrated alkali to produce dihydrogen gas? A) Copper (Cu) B) Silver (Ag) C) Aluminum (Al) D) Iron (Fe)
  6. The industrial preparation of dihydrogen from hydrocarbons involves: A) Electrolysis of water B) Brine electrolysis C) Steam reforming D) Bosch process
  7. A mixture of CO and H2 is known as: A) Producer gas B) Water gas C) Natural gas D) LPG
  8. The catalyst used in the water-gas shift reaction is: A) Ni B) Pt C) Iron Chromate D) V2O5
  9. Which property of dihydrogen makes it relatively unreactive at room temperature? A) Low melting point B) High H-H bond dissociation enthalpy C) Non-polar nature D) Lightest gas
  10. Dihydrogen is used in the hydrogenation of unsaturated hydrocarbons. The common catalysts used for this process are: A) Fe, Mo B) V2O5, Pt C) Ni, Pd, Pt D) AlCl3, BF3
  11. Metal hydrides formed by Group 1 and Group 2 elements (except Be, Mg) are typically: A) Covalent hydrides B) Metallic hydrides C) Ionic hydrides D) Electron-deficient hydrides
  12. Which of the following hydrides is electron-deficient? A) CH4 B) NH3 C) B2H6 D) H2O
  13. Which type of hydride is usually non-stoichiometric? A) Ionic hydrides B) Covalent hydrides C) Metallic hydrides D) Polymeric hydrides
  14. The bond angle in a water molecule (H2O) is approximately: A) 180 degrees B) 109.5 degrees C) 104.5 degrees D) 90 degrees
  15. The high boiling point of water is primarily due to: A) Covalent bonding B) Ionic bonding C) Extensive intermolecular hydrogen bonding D) High specific heat capacity
  16. Ice floats on water because: A) Ice is denser than water. B) Water is denser than ice. C) Ice has a higher specific heat than water. D) Water expands on freezing.
  17. Which of the following is an example of a species that acts as both a Bronsted-Lowry acid and a Bronsted-Lowry base? A) H+ B) OH- C) H2O D) Cl-
  18. Temporary hardness in water is caused by the presence of: A) Chlorides of Calcium and Magnesium B) Sulfates of Calcium and Magnesium C) Bicarbonates of Calcium and Magnesium D) Nitrates of Calcium and Magnesium
  19. Temporary hardness of water can be removed by: A) Adding washing soda B) Calgon method C) Boiling D) Ion-exchange method
  20. Which method can remove both temporary and permanent hardness of water completely? A) Boiling B) Clark’s method C) Ion-exchange method (using synthetic resins) D) Washing soda method
  21. De-ionized water is typically obtained by: A) Distillation B) Boiling hard water C) Synthetic resins method D) Adding lime
  22. The structure of hydrogen peroxide (H2O2) is: A) Linear B) Planar C) Non-planar (open book) D) Tetrahedral
  23. Hydrogen peroxide (H2O2) has a peroxide linkage, which is: A) H-O-O-H B) O=O C) O-H D) H-H
  24. Hydrogen peroxide is stored in dark plastic bottles because: A) It reacts with light. B) It reacts with glass. C) It is a strong acid. D) It is highly volatile.
  25. Which of the following is true about hydrogen peroxide (H2O2)? A) It acts only as an oxidizing agent. B) It acts only as a reducing agent. C) It can act as both an oxidizing and reducing agent. D) It is chemically inert.
  26. Hydrogen peroxide acts as an oxidizing agent in acidic medium by getting reduced to: A) O2 B) H2 C) H2O D) OH-
  27. Hydrogen peroxide acts as a reducing agent in acidic medium by getting oxidized to: A) O2 B) H2O C) H+ D) OH-
  28. The bleaching action of H2O2 is due to the release of: A) H+ ions B) OH- ions C) Nascent oxygen D) H2 gas
  29. The process of restoring the color of old lead paintings is done by treating them with: A) H2S B) H2O C) H2O2 D) O3
  30. The primary advantage of a hydrogen economy is: A) Low production cost B) Ease of storage C) Clean combustion product (water) D) High flammability
  31. Which of the following is an example of a metallic hydride? A) CH4 B) TiH1.7 C) NaH D) HF
  32. The process of producing syngas from coke and steam is known as: A) Haber’s process B) Water gas shift reaction C) Bosch process D) Water gas reaction
  33. Which of the following is NOT a property of ionic hydrides? A) Crystalline solids B) Volatile liquids or gases C) High melting points D) React violently with water to produce H2 gas
  34. In the electrolytic preparation of H2O2 from H2SO4, the intermediate formed is: A) H2SO3 B) H2S2O8 C) SO3 D) SO2
  35. The density anomaly of water (ice being less dense than liquid water) is maximum at which temperature? A) 0°C B) 4°C C) 100°C D) -4°C
  36. Which of the following elements forms an electron-rich hydride? A) Boron (B) B) Carbon (C) C) Nitrogen (N) D) Silicon (Si)
  37. The half-life of Tritium is: A) 12.33 years B) 1.233 years C) 123.3 years D) 1.233 days
  38. The hardest form of water is characterized by: A) Ability to readily form lather with soap. B) Presence of only sodium and potassium salts. C) Presence of dissolved calcium and magnesium salts. D) Absence of any dissolved minerals.
  39. The main challenge for hydrogen economy related to its physical state is: A) High reactivity B) Colourless and odourless nature C) Difficult storage and transportation D) Production cost
  40. Which of the following is a laboratory method for preparing dihydrogen? A) Electrolysis of acidified water B) Steam reforming of methane C) Reaction of Zn with dilute HCl D) Bosch process

Section 2: Answer Key

  1. C
  2. C
  3. A
  4. B
  5. C
  6. C
  7. B
  8. C
  9. B
  10. C
  11. C
  12. C
  13. C
  14. C
  15. C
  16. B
  17. C
  18. C
  19. C
  20. C
  21. C
  22. C
  23. A
  24. A
  25. C
  26. C
  27. A
  28. C
  29. C
  30. C
  31. B
  32. D
  33. B
  34. B
  35. B
  36. C
  37. A
  38. C
  39. C
  40. C

Section 3: Detailed Explanations

  1. C) It resembles both alkali metals and halogens.
    • Explanation: Hydrogen has 1s1 configuration, similar to alkali metals (ns1), allowing it to form H+. It also needs 1 electron to complete its duplet, similar to halogens, allowing it to form H- and diatomic molecules (H2).
  2. C) Tritium
    • Explanation: Protium and Deuterium are stable isotopes. Tritium (3H or T) is a radioactive beta-emitter.
  3. A) Protium
    • Explanation: Protium (1H) constitutes about 99.985% of all naturally occurring hydrogen.
  4. B) D2O
    • Explanation: Deuterium (D or 2H) is also known as heavy hydrogen, and its oxide, D2O, is called heavy water.
  5. C) Aluminum (Al)
    • Explanation: Certain metals like Zn and Al react with hot concentrated alkalis to produce dihydrogen. The reaction is: 2Al (s) + 2NaOH (aq) + 6H2O (l) -> 2Na[Al(OH)4] (aq) + 3H2 (g). Copper, Silver, and Iron do not react in this manner.
  6. C) Steam reforming
    • Explanation: The most common industrial method for large-scale production of dihydrogen is steam reforming of hydrocarbons (e.g., methane) or coke at high temperatures with a nickel catalyst.
  7. B) Water gas
    • Explanation: A mixture of carbon monoxide (CO) and hydrogen (H2) produced from coke and steam is called water gas (or syngas, if from hydrocarbons).
  8. C) Iron Chromate
    • Explanation: In the water-gas shift reaction (CO (g) + H2O (g) -> CO2 (g) + H2 (g)), iron chromate (FeCrO4 or Fe2O3/Cr2O3 mixture) is used as a catalyst at 673 K.
  9. B) High H-H bond dissociation enthalpy
    • Explanation: The H-H bond is very strong (436 kJ/mol), requiring significant energy to break. This makes dihydrogen relatively unreactive at room temperature.
  10. C) Ni, Pd, Pt
    • Explanation: Nickel (Ni), Palladium (Pd), and Platinum (Pt) are commonly used heterogeneous catalysts for the hydrogenation of unsaturated hydrocarbons (e.g., vegetable oil hardening).
  11. C) Ionic hydrides
    • Explanation: Group 1 (alkali metals) and Group 2 (alkaline earth metals, except Be and Mg due to higher covalent character) form ionic or saline hydrides where hydrogen exists as an H- ion.
  12. C) B2H6
    • Explanation: B2H6 (diborane) is an electron-deficient hydride from Group 13. It lacks sufficient electrons for conventional two-center two-electron bonds and exhibits unique bridge bonding. CH4 (electron-precise), NH3 and H2O (electron-rich).
  13. C) Metallic hydrides
    • Explanation: Metallic (or interstitial) hydrides, formed by d-block and f-block elements, are often non-stoichiometric, meaning their composition is variable (e.g., TiH1.5-1.8) because hydrogen occupies interstitial sites in the metal lattice.
  14. C) 104.5 degrees
    • Explanation: Water (H2O) has a bent or V-shaped structure. Oxygen is sp3 hybridized, but due to the presence of two lone pairs of electrons, the bond angle is compressed from the ideal tetrahedral angle of 109.5 degrees to approximately 104.5 degrees.
  15. C) Extensive intermolecular hydrogen bonding
    • Explanation: Water’s unusually high melting point, boiling point, specific heat, and other properties are all attributed to the extensive network of intermolecular hydrogen bonds formed between its molecules.
  16. B) Water is denser than ice.
    • Explanation: Ice floats on water because, due to hydrogen bonding, ice forms an open, cage-like structure where water molecules are less densely packed than in liquid water. Thus, ice is less dense than liquid water.
  17. C) H2O
    • Explanation: Water can accept a proton to form H3O+ (acting as a Bronsted-Lowry base) or donate a proton to form OH- (acting as a Bronsted-Lowry acid). Thus, it is amphoteric/amphiprotic.
  18. C) Bicarbonates of Calcium and Magnesium
    • Explanation: Temporary hardness is caused by the presence of soluble bicarbonates of calcium and magnesium, such as Ca(HCO3)2 and Mg(HCO3)2.
  19. C) Boiling
    • Explanation: Temporary hardness can be removed by simple boiling, which converts soluble bicarbonates into insoluble carbonates that precipitate out. Ca(HCO3)2 (aq) heat​ CaCO3 (s) + H2O (l) + CO2 (g)
  20. C) Ion-exchange method (using synthetic resins)
    • Explanation: The synthetic resins method (de-ionization or de-mineralization) is the most effective way to remove both temporary and permanent hardness completely by exchanging both cations (Ca2+, Mg2+) and anions (Cl-, SO4^2-, HCO3-) with H+ and OH- ions, respectively, yielding pure de-ionized water.
  21. C) Synthetic resins method
    • Explanation: The synthetic resins method, also known as the de-ionization or de-mineralization method, is used to produce highly pure de-ionized water by removing all dissolved ions.
  22. C) Non-planar (open book)
    • Explanation: Hydrogen peroxide has a non-planar, open book-like structure with a dihedral angle of about 111.5 degrees in the gas phase.
  23. A) H-O-O-H
    • Explanation: Hydrogen peroxide (H2O2) contains a peroxide linkage, which is an oxygen-oxygen single bond (-O-O-) with hydrogen atoms bonded to each oxygen.
  24. A) It reacts with light.
    • Explanation: Hydrogen peroxide slowly decomposes in the presence of light and certain metal surfaces or bases. Storing it in dark, plastic bottles prevents its decomposition.
  25. C) It can act as both an oxidizing and reducing agent.
    • Explanation: Hydrogen peroxide is a versatile compound. The oxidation state of oxygen in H2O2 is -1. It can be oxidized to O2 (0 oxidation state) (acting as a reducing agent) or reduced to H2O (-2 oxidation state) (acting as an oxidizing agent).
  26. C) H2O
    • Explanation: In acidic medium, H2O2 acts as a strong oxidizing agent, accepting electrons and getting reduced to water: H2O2 + 2H+ + 2e- -> 2H2O.
  27. A) O2
    • Explanation: When H2O2 acts as a reducing agent, it donates electrons and gets oxidized to oxygen gas: H2O2 -> O2 + 2H+ + 2e- (in acidic medium).
  28. C) Nascent oxygen
    • Explanation: The bleaching action of hydrogen peroxide is due to the release of highly reactive nascent oxygen atoms upon decomposition: H2O2 -> H2O + [O]. This nascent oxygen oxidizes coloring matter.
  29. C) H2O2
    • Explanation: Old lead paintings turn black due to the formation of lead sulfide (PbS) from atmospheric H2S. Hydrogen peroxide oxidizes black PbS to white lead sulfate (PbSO4), thus restoring the painting’s color: PbS (black) + 4H2O2 -> PbSO4 (white) + 4H2O.
  30. C) Clean combustion product (water)
    • Explanation: The main advantage of a hydrogen economy is that the combustion of hydrogen produces only water, making it a very clean and non-polluting fuel source. The other options are challenges or not unique advantages.
  31. B) TiH1.7
    • Explanation: Metallic (or non-stoichiometric) hydrides are formed by d-block and f-block elements. TiH1.7 is an example of a non-stoichiometric metallic hydride. CH4 is covalent, NaH is ionic, and HF is covalent.
  32. D) Water gas reaction
    • Explanation: The reaction C (s) + H2O (g) 1270K,Nicatalyst​ CO (g) + H2 (g) is known as the water gas reaction, producing water gas (syngas). The water gas shift reaction is a subsequent step to convert CO to CO2 to get more H2.
  33. B) Volatile liquids or gases
    • Explanation: Ionic hydrides are typically crystalline, non-volatile solids with high melting points. Volatile liquids or gases are characteristic of covalent/molecular hydrides.
  34. B) H2S2O8
    • Explanation: In the electrolytic method of H2O2 preparation, electrolysis of 30% H2SO4 (or ammonium sulfate solution) leads to the formation of peroxodisulfuric acid (H2S2O8) at the anode, which is then hydrolyzed to yield H2O2.
  35. B) 4°C
    • Explanation: Liquid water has its maximum density at 4°C. Above and below this temperature, its density decreases. Ice at 0°C is less dense than water at 4°C.
  36. C) Nitrogen (N)
    • Explanation: Electron-rich hydrides (Groups 15, 16, 17) have lone pairs on the central atom. Nitrogen forms NH3, which is an electron-rich hydride (one lone pair on N). Boron (B2H6) is electron-deficient. Carbon (CH4) and Silicon (SiH4) are electron-precise.
  37. A) 12.33 years
    • Explanation: Tritium (3H or T) is a radioactive isotope of hydrogen with a half-life of 12.33 years.
  38. C) Presence of dissolved calcium and magnesium salts.
    • Explanation: Hard water is characterized by the presence of dissolved salts of calcium (Ca2+) and magnesium (Mg2+), which prevent it from forming lather easily with soap.
  39. C) Difficult storage and transportation
    • Explanation: Hydrogen is a gas at standard conditions, making its storage (requires high pressure or cryogenic temperatures) and transportation challenging and expensive for a hydrogen economy.
  40. C) Reaction of Zn with dilute HCl
    • Explanation: Reacting active metals like zinc (Zn) with dilute acids (like HCl or H2SO4) is a common laboratory method for the preparation of dihydrogen gas. Electrolysis and steam reforming are industrial methods.

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