Here below some basic MCQ’s about “Boron, Carbon and Nitrogen” with answer which is explained in details. Let’s check one by one which is given below.
Q1. Which of the following is the most abundant element of Group 13 in Earth’s crust?
A) Boron
B) Aluminium
C) Gallium
D) Indium
Answer: B) Aluminium
Explanation: Aluminium is the most abundant metal in the Earth’s crust, making up about 8% by weight. Boron, although significant, is much less abundant. Gallium and indium are even rarer in comparison.
Q2. Which of the following oxides of boron is acidic?
A) B₂O₃
B) Al₂O₃
C) Ga₂O₃
D) In₂O₃
Answer: A) B₂O₃
Explanation: Boron forms acidic oxides (B₂O₃) due to its high electronegativity and small size. In contrast, aluminium and the heavier members (Ga, In) of Group 13 form amphoteric or basic oxides.
Q3. Boron forms covalent compounds, whereas aluminium forms ionic compounds because:
A) Boron has a larger atomic size.
B) Boron has higher electronegativity and ionization enthalpy.
C) Boron has a higher metallic character.
D) Boron forms stronger metallic bonds.
Answer: B) Boron has higher electronegativity and ionization enthalpy.
Explanation: Boron, being a small atom with high electronegativity and ionization energy, tends to form covalent bonds. Aluminium, being larger and less electronegative, can more easily lose electrons to form ionic bonds.
Q4. Which of the following elements of Group 14 shows the maximum tendency to catenate?
A) Carbon
B) Silicon
C) Germanium
D) Tin
Answer: A) Carbon
Explanation: Carbon exhibits the maximum ability to form long chains (catenation) due to its small atomic size and strong C-C bonds. As we go down the group, the catenation tendency decreases because of weaker bonds between heavier atoms.
Q5. The stability of +2 oxidation state increases down the group in Group 14 elements due to:
A) Inert pair effect
B) Decreasing electronegativity
C) Increase in atomic size
D) Increase in metallic character
Answer: A) Inert pair effect
Explanation: The inert pair effect refers to the reluctance of the s-electrons to participate in bonding. As we move down the group, this effect becomes more prominent, stabilizing the +2 oxidation state, particularly in lead (Pb).
Q6. Which of the following compounds is the strongest reducing agent?
A) SnCl₂
B) PbCl₂
C) GeCl₂
D) SiCl₄
Answer: A) SnCl₂
Explanation: Tin (Sn) in the +2 oxidation state is more stable than lead (Pb) due to the inert pair effect, making SnCl₂ a strong reducing agent.
Nitrogen Family (Group 15)
Q7. The allotropy of phosphorus is due to:
A) Different hybridization
B) Difference in atomic size
C) Difference in molecular structure
D) Variation in oxidation state
Answer: C) Difference in molecular structure
Explanation: Phosphorus exists in different allotropic forms like white, red, and black phosphorus. These forms arise due to different molecular structures rather than changes in hybridization or oxidation states.
Q8. The anomalous behavior of nitrogen compared to other elements of Group 15 is primarily due to:
A) Its small size
B) High electronegativity
C) Non-availability of d-orbitals
D) All of the above
Answer: D) All of the above
Explanation: Nitrogen is unique among the Group 15 elements because of its small atomic size, high electronegativity, and the absence of d-orbitals in its valence shell. This leads to different chemical behavior compared to heavier elements like phosphorus and arsenic.
Q9. Which of the following elements of Group 15 shows the highest metallic character?
A) Nitrogen
B) Phosphorus
C) Arsenic
D) Bismuth
Answer: D) Bismuth
Explanation: As we move down Group 15, metallic character increases due to the larger atomic size and lower ionization energy. Nitrogen is a non-metal, while bismuth is the most metallic element in this group.
Q10. Nitric oxide (NO) is different from other oxides of nitrogen because it:
A) Is paramagnetic
B) Is diamagnetic
C) Forms colored solutions
D) Exists in dimeric form
Answer: A) Is paramagnetic
Explanation: Nitric oxide (NO) has an odd number of electrons, making it paramagnetic. Other oxides of nitrogen, like N₂O and NO₂, either have even numbers of electrons or exist in different forms that lead to diamagnetism.
Boron Family
Q11. Boron hydrides, such as B₂H₆, exhibit unusual bonding known as:
A) Ionic bonding
B) Metallic bonding
C) Three-center two-electron bonds
D) Two-center two-electron bonds
Answer: C) Three-center two-electron bonds
Explanation: Boron in diborane (B₂H₆) exhibits electron-deficient bonding. The two boron atoms are bonded by hydrogen atoms using a three-center two-electron bond, which is characteristic of boron hydrides.
Q12. Which of the following reactions is used in the production of borax?
A) Boric acid is neutralized by sodium hydroxide
B) Boron reacts with hydrochloric acid
C) Colemanite reacts with sodium carbonate
D) Aluminium is reacted with boron trioxide
Answer: C) Colemanite reacts with sodium carbonate
Explanation: Borax (Na₂B₄O₇·10H₂O) is obtained by reacting colemanite (Ca₂B₆O₁₁·5H₂O) with sodium carbonate, leading to the formation of borax.
Q13. Which of the following statements about aluminium is false?
A) It is a good conductor of electricity.
B) It is more reactive than iron.
C) It forms a protective oxide layer.
D) It is a heavier metal than iron.
Answer: D) It is a heavier metal than iron.
Explanation: Aluminium is actually a lighter metal compared to iron. It is known for being light and strong, making it useful in industries like aviation.
Q14. Boric acid (H₃BO₃) behaves as a weak acid because:
A) It donates protons in water.
B) It accepts hydroxide ions.
C) It dissociates completely in water.
D) It is a strong electrolyte.
Answer: B) It accepts hydroxide ions.
Explanation: Boric acid acts as a Lewis acid by accepting OH⁻ ions from water rather than donating protons (H⁺). This reaction produces B(OH)₄⁻ ions and makes boric acid behave as a weak acid.
Q15. The most stable oxidation state of thallium is:
A) +1
B) +2
C) +3
D) +5
Answer: A) +1
Explanation: Thallium shows the +1 oxidation state as the most stable due to the inert pair effect, where the 6s electrons are reluctant to participate in bonding.
Q16. Which of the following statements is true for the compounds of aluminium?
A) Aluminium oxide is amphoteric.
B) Aluminium chloride exists as a dimer in the gas phase.
C) Aluminium has low ionization energy compared to boron.
D) All of the above.
Answer: D) All of the above
Explanation: Aluminium oxide (Al₂O₃) is amphoteric, reacting with both acids and bases. In the gas phase, AlCl₃ exists as a dimer (Al₂Cl₆) to satisfy the octet rule. Aluminium has lower ionization energy compared to boron due to its larger atomic size.
Carbon Family
Q17. The general oxidation states shown by the elements of Group 14 are:
A) +1 and +2
B) +2 and +3
C) +4 and +2
D) +3 and +5
Answer: C) +4 and +2
Explanation: Group 14 elements exhibit +4 oxidation states as their primary oxidation state, but as we go down the group, the +2 oxidation state becomes more stable due to the inert pair effect.
Q18. Carbon tetrachloride (CCl₄) does not hydrolyze easily because:
A) Carbon is not reactive.
B) Chlorine atoms are strongly bonded to carbon.
C) Carbon does not have vacant d-orbitals.
D) Water does not react with non-polar compounds.
Answer: C) Carbon does not have vacant d-orbitals.
Explanation: Carbon lacks vacant d-orbitals to accept lone pairs from water, so CCl₄ does not hydrolyze easily. In contrast, silicon tetrachloride (SiCl₄) hydrolyzes because silicon has vacant d-orbitals.
Q19. Which of the following shows the highest tendency for catenation?
A) Silicon
B) Carbon
C) Germanium
D) Tin
Answer: B) Carbon
Explanation: Carbon’s ability to form long chains and rings (catenation) is due to its strong C-C bonds and small size, making it the most prominent element for catenation among Group 14.
Q20. Diamond has a high melting point because:
A) It is a molecular solid.
B) It is made of ionic bonds.
C) It has a three-dimensional network of covalent bonds.
D) It contains weak van der Waals forces.
Answer: C) It has a three-dimensional network of covalent bonds.
Explanation: Diamond consists of a three-dimensional lattice where each carbon atom is covalently bonded to four other carbon atoms, giving it exceptional hardness and a high melting point.
Q21. Lead (IV) compounds are less stable than lead (II) compounds due to:
A) Greater metallic character of lead.
B) Higher electronegativity of lead.
C) Inert pair effect.
D) Smaller atomic size of lead.
Answer: C) Inert pair effect
Explanation: The inert pair effect causes the s-electrons to remain paired and not participate in bonding, making the +2 oxidation state more stable for lead than the +4 oxidation state.
Q22. Which of the following elements of Group 14 forms both ionic and covalent halides?
A) Carbon
B) Silicon
C) Germanium
D) Lead
Answer: D) Lead
Explanation: Lead forms covalent compounds like PbCl₄ in the +4 oxidation state and ionic compounds like PbCl₂ in the +2 oxidation state, reflecting the stability of the +2 state due to the inert pair effect.
Q23. The strongest allotrope of carbon is:
A) Graphite
B) Diamond
C) Fullerene
D) Carbon nanotubes
Answer: B) Diamond
Explanation: Diamond is the hardest known natural material because of its tetrahedral structure, where each carbon atom is strongly covalently bonded to four other carbon atoms.
Q24. Silica (SiO₂) has a structure similar to:
A) Diamond
B) Graphite
C) Fullerene
D) NaCl
Answer: A) Diamond
Explanation: Silica (SiO₂) has a network covalent structure similar to diamond, where each silicon atom is bonded to four oxygen atoms in a tetrahedral arrangement, leading to a rigid 3D structure.
Nitrogen Family
Q25. Nitrogen exists as a diatomic molecule, whereas phosphorus exists as:
A) Diatomic molecules
B) P₄ molecules
C) P₃ molecules
D) P₂ molecules
Answer: B) P₄ molecules
Explanation: Nitrogen forms stable diatomic molecules (N₂) with a triple bond. Phosphorus, on the other hand, exists as P₄ tetrahedral molecules due to its inability to form strong triple bonds like nitrogen.
Q26. The anomalous behavior of nitrogen among Group 15 elements is due to:
A) Absence of d-orbitals
B) High electronegativity
C) Small atomic size
D) All of the above
Answer: D) All of the above
Explanation: Nitrogen differs from other Group 15 elements because it has no d-orbitals, high electronegativity, and small atomic size. These factors lead to its unique properties like the formation of N₂ with a triple bond.
Q27. Ammonia (NH₃) has a higher boiling point than phosphine (PH₃) because:
A) Ammonia is heavier.
B) Ammonia forms hydrogen bonds.
C) Ammonia has a larger molecular size.
D) Ammonia is a polar molecule.
Answer: B) Ammonia forms hydrogen bonds.
Explanation: Ammonia molecules form strong intermolecular hydrogen bonds due to the high electronegativity of nitrogen, leading to a higher boiling point compared to phosphine, which does not form hydrogen bonds as effectively.
Q28. Nitric acid (HNO₃) acts as a strong acid because:
A) It dissociates completely in water.
B) It is a weak electrolyte.
C) It forms covalent bonds in water.
D) It is amphoteric.
Answer: A) It dissociates completely in water.
Explanation: Nitric acid (HNO₃) is a strong acid that dissociates completely in water to produce H⁺ and NO₃⁻ ions, making it highly acidic.
Q29. Phosphorus pentachloride (PCl₅) in solid state exists as:
A) PCl₅ molecules
B) PCl₄⁺ and PCl₆⁻ ions
C) P₂Cl₁₀ molecules
D) P₄ molecules
Answer: B) PCl₄⁺ and PCl₆⁻ ions
Explanation: In the solid state, PCl₅ exists in the ionic form as PCl₄⁺ and PCl₆⁻ ions, which stabilize the solid structure. In the gaseous state, PCl₅ exists as discrete molecules.
Q30. The most stable oxidation state of bismuth (Bi) is:
A) +1
B) +3
C) +5
D) -3
Answer: B) +3
Explanation: Due to the inert pair effect, the +3 oxidation state is the most stable for bismuth, with the +5 oxidation state being less stable as we go down the group.
Q31. Which of the following compounds of nitrogen is used in the manufacture of explosives?
A) Ammonium nitrate
B) Sodium nitrate
C) Nitrogen dioxide
D) Urea
Answer: A) Ammonium nitrate
Explanation: Ammonium nitrate is commonly used in explosives because of its ability to decompose rapidly, releasing a large amount of gas and energy.
Q32. Which of the following elements forms an acidic oxide?
A) Nitrogen
B) Phosphorus
C) Bismuth
D) Arsenic
Answer: A) Nitrogen
Explanation: Nitrogen forms acidic oxides such as NO₂ and N₂O₅, which dissolve in water to form acids. Phosphorus and arsenic also form acidic oxides, but nitrogen oxides are more acidic.
Q33. Which of the following is a property of white phosphorus?
A) It is soluble in water.
B) It glows in the dark (chemiluminescence).
C) It is a conductor of electricity.
D) It is non-reactive at room temperature.
Answer: B) It glows in the dark (chemiluminescence).
Explanation: White phosphorus exhibits chemiluminescence, glowing in the dark due to the slow oxidation of phosphorus in air, releasing light energy.
Q34. The bond angle in ammonia (NH₃) is approximately:
A) 120°
B) 109.5°
C) 107°
D) 104.5°
Answer: C) 107°
Explanation: The bond angle in ammonia is approximately 107° due to the lone pair of electrons on the nitrogen atom, which repels the bond pairs, reducing the ideal tetrahedral angle (109.5°).
Q35. Which of the following oxides of nitrogen is a neutral oxide?
A) NO
B) N₂O₃
C) NO₂
D) N₂O₅
Answer: A) NO
Explanation: Nitric oxide (NO) is a neutral oxide, meaning it does not show acidic or basic properties in water. Other nitrogen oxides like NO₂ and N₂O₅ are acidic.
Q36. The Haber process is used to synthesize:
A) Nitric acid
B) Ammonia
C) Urea
D) Nitrogen dioxide
Answer: B) Ammonia
Explanation: The Haber process is an industrial method for synthesizing ammonia (NH₃) by reacting nitrogen (N₂) and hydrogen (H₂) under high pressure and temperature in the presence of a catalyst.
Q37. Which of the following is the main constituent of the Earth’s atmosphere?
A) Oxygen
B) Nitrogen
C) Argon
D) Carbon dioxide
Answer: B) Nitrogen
Explanation: Nitrogen makes up about 78% of the Earth’s atmosphere, making it the most abundant gas, followed by oxygen at around 21%.
Q38. The oxidation state of nitrogen in nitric acid (HNO₃) is:
A) +3
B) +5
C) -3
D) 0
Answer: B) +5
Explanation: In nitric acid (HNO₃), nitrogen is in the +5 oxidation state, as the molecule consists of one nitrogen atom bonded to three oxygen atoms, with nitrogen losing five electrons in total.
Q39. Phosphorus forms halides in the oxidation states of:
A) +1 and +3
B) +2 and +4
C) +3 and +5
D) +4 and +6
Answer: C) +3 and +5
Explanation: Phosphorus typically forms halides in the +3 (e.g., PCl₃) and +5 (e.g., PCl₅) oxidation states, reflecting its ability to exhibit multiple oxidation states.
Q40. Which of the following compounds is used as a fertilizer?
A) Ammonium nitrate
B) Ammonium chloride
C) Sodium chloride
D) Urea
Answer: D) Urea
Explanation: Urea (NH₂CONH₂) is a widely used nitrogen fertilizer, as it provides a source of nitrogen to plants, which is essential for their growth.
Q41. Which of the following hydrides of nitrogen is the most basic?
A) NH₃
B) N₂H₄
C) NH₂OH
D) HNO₃
Answer: A) NH₃
Explanation: Ammonia (NH₃) is the most basic hydride of nitrogen due to the presence of a lone pair of electrons on nitrogen, which makes it a good proton acceptor.
Q42. The phosphorus allotrope that is used in the manufacture of safety matches is:
A) White phosphorus
B) Red phosphorus
C) Black phosphorus
D) Violet phosphorus
Answer: B) Red phosphorus
Explanation: Red phosphorus is used in safety matches due to its lower reactivity compared to white phosphorus, making it safer to handle.
Q43. The oxidation state of carbon in carbon dioxide (CO₂) is:
A) +2
B) +4
C) -4
D) 0
Answer: B) +4
Explanation: In CO₂, carbon is in the +4 oxidation state because each oxygen atom takes two electrons from the carbon, making carbon lose four electrons.
Q44. Silicon is widely used in the electronics industry because of its:
A) High electrical conductivity
B) Low reactivity
C) Semiconducting properties
D) Abundance
Answer: C) Semiconducting properties
Explanation: Silicon is used in the electronics industry due to its semiconducting properties, making it suitable for making transistors, diodes, and other electronic devices.
Q45. Which of the following elements of Group 14 forms the strongest covalent bonds?
A) Carbon
B) Silicon
C) Germanium
D) Tin
Answer: A) Carbon
Explanation: Carbon forms the strongest covalent bonds due to its small atomic size and ability to form stable bonds with itself and other elements.
Q46. Lead-acid batteries contain which of the following compounds of lead?
A) Lead oxide
B) Lead dioxide
C) Lead carbonate
D) Lead nitrate
Answer: B) Lead dioxide
Explanation: Lead-acid batteries contain lead dioxide (PbO₂) as the cathode material, which plays a crucial role in the electrochemical reactions of the battery.
Q47. The strongest allotrope of carbon is:
A) Graphite
B) Diamond
C) Fullerene
D) Graphene
Answer: B) Diamond
Explanation: Diamond is the hardest known natural material due to its three-dimensional covalent bond network, where each carbon atom is bonded to four others.
Q48. In which of the following compounds does carbon exhibit sp hybridization?
A) Ethyne
B) Ethene
C) Ethane
D) Carbon dioxide
Answer: A) Ethyne
Explanation: In ethyne (C₂H₂), carbon exhibits sp hybridization due to the triple bond between the carbon atoms, where one sigma bond and two pi bonds are formed.
Q49. The molecular geometry of methane (CH₄) is:
A) Trigonal planar
B) Linear
C) Tetrahedral
D) Square planar
Answer: C) Tetrahedral
Explanation: Methane (CH₄) has a tetrahedral geometry with bond angles of approximately 109.5°, as each hydrogen atom is bonded to carbon in a symmetrical arrangement.
Q50. Silicon dioxide (SiO₂) has a structure similar to:
A) Diamond
B) Graphite
C) Fullerene
D) Graphene
Answer: A) Diamond
Explanation: Silicon dioxide (SiO₂) has a network covalent structure similar to diamond, with each silicon atom bonded to four oxygen atoms in a tetrahedral arrangement.
Boron Family (Group 13)
Q51. Aluminium reacts with atmospheric oxygen to form a protective layer of:
A) Al₂O₃
B) Al(OH)₃
C) AlO₃
D) Al₂O₄
Answer: A) Al₂O₃
Explanation: Aluminium forms a protective oxide layer of Al₂O₃ when exposed to air. This layer prevents further oxidation and corrosion of the metal.
Q52. Which of the following compounds of boron is used as a neutron absorber in nuclear reactors?
A) Boric acid
B) Boron nitride
C) Borax
D) Diborane
Answer: A) Boric acid
Explanation: Boric acid is used in nuclear reactors as a neutron absorber due to the high neutron-capturing ability of boron-10 isotope, which helps control the fission reaction.
Q53. The compound BF₃ behaves as:
A) A Lewis base
B) A Lewis acid
C) A strong electrolyte
D) A strong base
Answer: B) A Lewis acid
Explanation: BF₃ is an electron-deficient compound with only six electrons around boron, so it readily accepts electrons, making it a Lewis acid.
Q54. Which of the following boron halides is the least volatile?
A) BF₃
B) BCl₃
C) BBr₃
D) BI₃
Answer: D) BI₃
Explanation: The volatility decreases down the group with increasing molecular mass. BI₃ is the least volatile because of its large atomic size and stronger van der Waals forces.
Q55. What is the hybridization of boron in boric acid (H₃BO₃)?
A) sp
B) sp²
C) sp³
D) dsp²
Answer: B) sp²
Explanation: In boric acid, boron is surrounded by three oxygen atoms, and the geometry is trigonal planar, which corresponds to sp² hybridization.
Q56. Which of the following is a correct statement about the electronic configuration of aluminium?
A) [Ne] 3s² 3p¹
B) [Ar] 4s² 4p¹
C) [Ne] 3s² 3p²
D) [He] 2s² 2p¹
Answer: A) [Ne] 3s² 3p¹
Explanation: Aluminium has 13 electrons. The correct electronic configuration is [Ne] 3s² 3p¹.
Carbon Family (Group 14)
Q57. The allotrope of carbon that is a good conductor of electricity is:
A) Diamond
B) Graphite
C) Fullerene
D) Carbon nanotubes
Answer: B) Graphite
Explanation: Graphite conducts electricity because its structure consists of layers of carbon atoms with free-moving delocalized electrons between the layers.
Q58. The most stable oxide of carbon is:
A) CO₂
B) CO
C) C₂O
D) C₂O₃
Answer: A) CO₂
Explanation: Carbon dioxide (CO₂) is the most stable oxide of carbon. Carbon monoxide (CO) is less stable due to its partial oxidation state.
Q59. Silicon carbide (SiC) is commonly used as:
A) A semiconductor
B) A reducing agent
C) An abrasive
D) A fertilizer
Answer: C) An abrasive
Explanation: Silicon carbide (SiC), also known as carborundum, is extremely hard and is used as an abrasive material for cutting and grinding.
Q60. The inert pair effect is more prominent in which of the following elements?
A) Carbon
B) Silicon
C) Germanium
D) Lead
Answer: D) Lead
Explanation: The inert pair effect becomes more prominent as you go down the group in Group 14 elements. In lead (Pb), the 6s² electrons are reluctant to participate in bonding, making the +2 oxidation state more stable than the +4 state.
Q61. Which of the following compounds of carbon is used as a refrigerant?
A) Carbon dioxide
B) Methane
C) Carbon tetrafluoride
D) Freon-12
Answer: D) Freon-12
Explanation: Freon-12 (CCl₂F₂) is a chlorofluorocarbon (CFC) that was used as a refrigerant. However, its use has been reduced due to its harmful effects on the ozone layer.
Q62. The hybridization of carbon in acetylene (C₂H₂) is:
A) sp
B) sp²
C) sp³
D) None of the above
Answer: A) sp
Explanation: In acetylene (C₂H₂), carbon forms a triple bond, leading to sp hybridization with two pi bonds and one sigma bond.
Q63. The stability of carbon compounds is mainly due to:
A) High bond energy of C-C bonds
B) High electronegativity of carbon
C) Ability to form multiple bonds
D) All of the above
Answer: D) All of the above
Explanation: Carbon compounds are stable due to the high bond energy of C-C bonds, its moderate electronegativity, and its ability to form multiple bonds (like C=C and C≡C).
Nitrogen Family (Group 15)
Q64. The most stable allotrope of phosphorus is:
A) White phosphorus
B) Red phosphorus
C) Black phosphorus
D) Violet phosphorus
Answer: B) Red phosphorus
Explanation: Red phosphorus is the most stable allotrope of phosphorus at room temperature, whereas white phosphorus is more reactive and less stable.
Q65. Which of the following nitrogen oxides is a colorless gas?
A) N₂O
B) NO₂
C) N₂O₃
D) N₂O₅
Answer: A) N₂O
Explanation: Nitrous oxide (N₂O), commonly known as laughing gas, is a colorless gas, while other nitrogen oxides like NO₂ are colored gases.
Q66. Ammonia (NH₃) is a:
A) Strong acid
B) Weak base
C) Strong base
D) Weak acid
Answer: B) Weak base
Explanation: Ammonia is a weak base due to its ability to accept a proton (H⁺) in water, forming ammonium ions (NH₄⁺) and hydroxide ions (OH⁻).
Q67. Phosphorus pentoxide (P₂O₅) reacts with water to form:
A) Phosphoric acid
B) Phosphorous acid
C) Hypophosphoric acid
D) Pyrophosphoric acid
Answer: A) Phosphoric acid
Explanation: Phosphorus pentoxide reacts with water to form phosphoric acid (H₃PO₄) through the following reaction:
P2O5+3H2O→2H3PO4P2O5+3H2O→2H3PO4
Q68. Which of the following is used in the manufacture of nitric acid?
A) Ammonia
B) Nitrogen
C) Nitrous oxide
D) Phosphine
Answer: A) Ammonia
Explanation: Nitric acid is produced through the Ostwald process, where ammonia (NH₃) is oxidized to nitric acid (HNO₃) using oxygen and a platinum catalyst.
Q69. Which of the following has the highest boiling point?
A) NH₃
B) PH₃
C) AsH₃
D) SbH₃
Answer: A) NH₃
Explanation: Ammonia (NH₃) has the highest boiling point among the hydrides of Group 15 due to the presence of strong hydrogen bonds.
Q70. The oxidation state of nitrogen in nitrous oxide (N₂O) is:
A) +1
B) +2
C) +3
D) +4
Answer: A) +1
Explanation: In N₂O (nitrous oxide), nitrogen has an oxidation state of +1, with one nitrogen atom in a 0 oxidation state and the other in a +2 state, giving an average of +1.
Q71. Phosphine (PH₃) is:
A) A reducing agent
B) An oxidizing agent
C) Amphoteric
D) Neutral
Answer: A) A reducing agent
Explanation: Phosphine (PH₃) acts as a reducing agent because phosphorus can be easily oxidized due to its low electronegativity and weak P-H bonds.
Q72. The bond angle in phosphine (PH₃) is less than ammonia (NH₃) because:
A) Phosphorus is larger than nitrogen
B) Lone pair-lone pair repulsion is greater in PH₃
C) Electronegativity of phosphorus is lower
D) The molecular size of PH₃ is smaller
Answer: C) Electronegativity of phosphorus is lower
Explanation: The lower electronegativity of phosphorus compared to nitrogen causes less electron repulsion in the P-H bonds, resulting in a smaller bond angle in PH₃ than in NH₃.
Q73. The element that shows the greatest tendency to form pπ–pπ multiple bonds is:
A) Nitrogen
B) Phosphorus
C) Arsenic
D) Antimony
Answer: A) Nitrogen
Explanation: Nitrogen, being the smallest in size among Group 15 elements, forms strong pπ–pπ multiple bonds such as N≡N in nitrogen gas (N₂), due to its ability to overlap efficiently.
Q74. The compound N₂O₃ is:
A) Acidic
B) Basic
C) Neutral
D) Amphoteric
Answer: A) Acidic
Explanation: Nitrogen trioxide (N₂O₃) is an acidic oxide. When dissolved in water, it forms nitrous acid (HNO₂).
Q75. Which of the following statements is correct about boron nitride (BN)?
A) It is a good conductor of electricity.
B) It has a structure similar to graphite.
C) It is used as a fertilizer.
D) It is amphoteric.
Answer: B) It has a structure similar to graphite.
Explanation: Boron nitride exists in two forms: hexagonal BN, which has a structure similar to graphite, and cubic BN, which resembles diamond in structure.
Q76. In which of the following reactions does phosphorus act as an oxidizing agent?
A) P₄ + 3NaOH + 3H₂O → PH₃ + NaH₂PO₂
B) P₄ + 10Cl₂ → 4PCl₅
C) PCl₅ → PCl₃ + Cl₂
D) 2P + 3Cl₂ → 2PCl₃
Answer: B) P₄ + 10Cl₂ → 4PCl₅
Explanation: In this reaction, phosphorus (P) is oxidized from 0 to +5 oxidation state in PCl₅, thus acting as an oxidizing agent.
Q77. The highest oxidation state of nitrogen in its compounds is:
A) +3
B) +4
C) +5
D) +1
Answer: C) +5
Explanation: The highest oxidation state nitrogen can achieve is +5, as seen in compounds like nitric acid (HNO₃) and nitrogen pentoxide (N₂O₅).
Q78. Which of the following statements about urea is correct?
A) It is an acidic compound.
B) It contains an amide functional group.
C) It is used as a pesticide.
D) It is synthesized from ammonia and nitric acid.
Answer: B) It contains an amide functional group.
Explanation: Urea (NH₂CONH₂) contains two amide groups attached to a carbonyl group. It is widely used as a nitrogen fertilizer.
Q79. Which of the following elements has the highest first ionization energy?
A) Carbon
B) Nitrogen
C) Oxygen
D) Boron
Answer: B) Nitrogen
Explanation: Nitrogen has the highest first ionization energy due to its half-filled 2p orbitals, which provide extra stability.
Q80. Which of the following compounds is not a hydride of nitrogen?
A) Hydrazine (N₂H₄)
B) Ammonia (NH₃)
C) Hydroxylamine (NH₂OH)
D) Nitric acid (HNO₃)
Answer: D) Nitric acid (HNO₃)
Explanation: Nitric acid is an oxoacid of nitrogen, not a hydride. The others are all hydrides containing N-H bonds.
Q81. Phosphorus pentachloride (PCl₅) behaves as an ionic compound in:
A) Solid state
B) Liquid state
C) Gaseous state
D) Aqueous solution
Answer: A) Solid state
Explanation: In the solid state, PCl₅ exists as an ionic compound consisting of PCl₄⁺ and PCl₆⁻ ions. In the gaseous and liquid states, it exists as discrete PCl₅ molecules.
Q82. The only noble gas compound of nitrogen is:
A) XeF₄
B) XeF₆
C) XeO₄
D) XeONF
Answer: D) XeONF
Explanation: Xenon oxynitride fluoride (XeONF) is one of the few known compounds containing both nitrogen and a noble gas (xenon).
Q83. Which of the following is not a property of black phosphorus?
A) It has a layered structure.
B) It is a good conductor of electricity.
C) It is more stable than white phosphorus.
D) It is highly reactive.
Answer: D) It is highly reactive.
Explanation: Black phosphorus is the least reactive allotrope of phosphorus, unlike white phosphorus, which is highly reactive. It has a layered structure and is more stable.
Q84. Carbon tetrachloride (CCl₄) is widely used as a:
A) Solvent for organic compounds
B) Fertilizer
C) Reducing agent
D) Refrigerant
Answer: A) Solvent for organic compounds
Explanation: Carbon tetrachloride is a non-polar solvent used to dissolve non-polar organic compounds. However, its use has declined due to its toxicity and environmental impact.
Q85. Which of the following pairs of oxides are amphoteric?
A) CO₂ and SiO₂
B) Al₂O₃ and SnO₂
C) PbO₂ and CO
D) NO₂ and N₂O₅
Answer: B) Al₂O₃ and SnO₂
Explanation: Both aluminium oxide (Al₂O₃) and tin dioxide (SnO₂) are amphoteric, meaning they can react with both acids and bases.
Q86. Diborane (B₂H₆) contains:
A) Two three-center two-electron bonds
B) Two three-center three-electron bonds
C) Two three-center four-electron bonds
D) Two four-center two-electron bonds
Answer: A) Two three-center two-electron bonds
Explanation: Diborane contains two three-center two-electron (3c–2e) bonds, also known as banana bonds, which involve two boron atoms and one hydrogen atom sharing two electrons.
Q87. Which of the following oxides of nitrogen is paramagnetic?
A) N₂O
B) NO
C) NO₂
D) N₂O₅
Answer: B) NO
Explanation: Nitric oxide (NO) is paramagnetic due to the presence of an unpaired electron, while other nitrogen oxides are diamagnetic.
Q88. Which of the following elements of Group 13 is a metalloid?
A) Boron
B) Aluminium
C) Gallium
D) Indium
Answer: A) Boron
Explanation: Boron is a metalloid, possessing both metallic and non-metallic properties. Other Group 13 elements, such as aluminium and gallium, are metals.
Q89. The chemical formula of borax is:
A) Na₂B₄O₇·10H₂O
B) Na₂B₂O₅·5H₂O
C) Na₂B₄O₅·5H₂O
D) Na₂B₆O₁₁·10H₂O
Answer: A) Na₂B₄O₇·10H₂O
Explanation: Borax has the chemical formula Na₂B₄O₇·10H₂O. It is a hydrate of sodium tetraborate and is used in cleaning and laundry detergents.
Q90. In the Contact process for the manufacture of sulfuric acid, the catalyst used is:
A) Manganese dioxide
B) Vanadium pentoxide
C) Platinum
D) Iron oxide
Answer: B) Vanadium pentoxide
Explanation: Vanadium pentoxide (V₂O₅) is used as a catalyst in the Contact process to oxidize sulfur dioxide (SO₂) to sulfur trioxide (SO₃), which is then converted to sulfuric acid.
Q91. Which of the following compounds does not exist?
A) NCl₃
B) PCl₅
C) BiCl₅
D) PF₅
Answer: C) BiCl₅
Explanation: Bismuth (Bi) does not form BiCl₅ due to the inert pair effect. It commonly exhibits a +3 oxidation state, so BiCl₃ exists, but BiCl₅ does not.
Q92. Which of the following is a non-metallic oxide?
A) B₂O₃
B) PbO
C) CO
D) SnO₂
Answer: A) B₂O₃
Explanation: Boron trioxide (B₂O₃) is a non-metallic oxide of boron. Lead oxide (PbO), carbon monoxide (CO), and tin dioxide (SnO₂) are metallic or semi-metallic oxides.
Q93. Which of the following oxides of nitrogen is commonly known as “laughing gas”?
A) NO₂
B) N₂O
C) NO
D) N₂O₅
Answer: B) N₂O
Explanation: Nitrous oxide (N₂O) is commonly known as laughing gas due to its euphoric effects when inhaled. It is used as an anesthetic and analgesic in medicine.
Q94. Which of the following statements is correct for boron?
A) It forms only covalent compounds.
B) It forms ionic as well as covalent compounds.
C) It exists as a liquid at room temperature.
D) It is a poor conductor of electricity.
Answer: A) It forms only covalent compounds.
Explanation: Boron, being a small non-metal, forms only covalent compounds, unlike other elements in its group that can form both ionic and covalent compounds.
Q95. The process by which nitrogen is fixed into ammonia in the Haber process involves:
A) High temperature and pressure
B) Low temperature and high pressure
C) Low temperature and pressure
D) Moderate temperature and high pressure
Answer: A) High temperature and pressure
Explanation: In the Haber process, nitrogen and hydrogen gases are reacted at high temperature (400-500°C) and high pressure (200-300 atm) with an iron catalyst to form ammonia (NH₃).
Q96. Which of the following compounds is used in matches?
A) Red phosphorus
B) White phosphorus
C) Phosphine
D) Phosphorus pentoxide
Answer: A) Red phosphorus
Explanation: Red phosphorus is used on the striking surfaces of matchboxes due to its stability and relatively safe reaction with the oxidizing agents present in match heads.
Q97. What is the major product formed when aluminium reacts with chlorine?
A) AlCl₂
B) AlCl₃
C) Al₂Cl₅
D) AlCl
Answer: B) AlCl₃
Explanation: Aluminium reacts with chlorine to form aluminium chloride (AlCl₃) in a 1:3 stoichiometric ratio. AlCl₃ is an important compound used in various chemical processes.
Q98. The hydrolysis of PCl₅ in water leads to the formation of:
A) HCl and POCl₃
B) HCl and H₃PO₄
C) HCl and PCl₃
D) HCl and H₃PO₂
Answer: B) HCl and H₃PO₄
Explanation: The hydrolysis of phosphorus pentachloride (PCl₅) with water produces hydrochloric acid (HCl) and phosphoric acid (H₃PO₄).
Q99. Which of the following forms the strongest hydrogen bonds?
A) Ammonia
B) Phosphine
C) Arsenic hydride
D) Antimony hydride
Answer: A) Ammonia
Explanation: Ammonia (NH₃) forms strong hydrogen bonds due to the high electronegativity of nitrogen and the presence of lone pairs of electrons.
Q100. Which of the following hydrides of Group 15 is the least thermally stable?
A) NH₃
B) PH₃
C) AsH₃
D) SbH₃
Answer: D) SbH₃
Explanation: The thermal stability of hydrides decreases down the group. Antimony hydride (SbH₃) is the least stable because of the large atomic size and weak bonding in the Sb-H bond.
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