1. Which statement correctly explains why graphite is softer than diamond despite both being carbon allotropes?
- (A) Graphite has stronger covalent bonds within layers
- (B) Diamond lacks delocalized electrons
- (C) Graphite's layers can slide due to weak van der Waals forces between them
- (D) Diamond has sp² hybridization while graphite has sp³
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Correct Answer: (C) Graphite's layers can slide due to weak van der Waals forces between them
Explanation: Graphite's softness arises from weak interlayer forces allowing layer sliding, while its intralayer covalent bonds remain strong. Diamond's 3D network covalent structure makes it hard.2. Which property is shared by both metallic and ionic solids?
- (A) Malleability and ductility
- (B) Electrical conductivity in solid state
- (C) High vapor pressure at room temperature
- (D) Formation of crystal lattices
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Correct Answer: (D) Formation of crystal lattices
Explanation: Both metallic and ionic solids form ordered crystal lattice structures, though their bonding differs (metallic bonds vs. ionic bonds).3. According to Coulomb's law, which compound has the strongest ionic bonds?
- (A) NaCl
- (B) LiF
- (C) MgO
- (D) KBr
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Correct Answer: (C) MgO
Explanation: Bond strength ∝ (q₁q₂)/r. Mg²⁺ and O²⁻ have higher charges (2+ and 2-) and smaller ionic radii than other options.4. Which substance is a network covalent solid?
- (A) Dry ice (CO₂)
- (B) Graphite (C)
- (C) Sodium chloride (NaCl)
- (D) Copper (Cu)
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Correct Answer: (B) Graphite (C)
Explanation: Graphite forms extended covalent networks through sp² hybridization, characteristic of network covalent solids.5. Which molecule has resonance structures?
- (A) CH₄
- (B) NH₃
- (C) CO₃²⁻
- (D) H₂O
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Correct Answer: (C) CO₃²⁻
Explanation: Carbonate ion exhibits resonance with three equivalent structures where double bond position rotates, delocalizing electrons.6. What is the formal charge on oxygen in carbon monoxide (C≡O)?
- (A) +1
- (B) -1
- (C) 0
- (D) +2
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Correct Answer: (B) -1
Explanation: Formal charge = 6 - (2 + 6/2) = -1. Oxygen has 6 valence e⁻, 2 lone e⁻, and 3 bonds (6 shared e⁻).7. Which describes the electron geometry of SF₄?
- (A) Tetrahedral
- (B) Trigonal bipyramidal
- (C) See-saw
- (D) Octahedral
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Correct Answer: (B) Trigonal bipyramidal
Explanation: SF₄ has 5 electron domains (4 bonds + 1 lone pair), resulting in trigonal bipyramidal electron geometry.8. Which alloy type has components with significantly different atomic radii?
- (A) Substitutional alloy
- (B) Interstitial alloy
- (C) Both A and B
- (D) Neither A nor B
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Correct Answer: (B) Interstitial alloy
Explanation: Interstitial alloys form when smaller atoms occupy spaces between larger host atoms, requiring different radii.9. What hybridization occurs in BF₃?
- (A) sp
- (B) sp²
- (C) sp³
- (D) dsp³
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Correct Answer: (B) sp²
Explanation: BF₃ has trigonal planar geometry with 120° bond angles, indicating sp² hybridization.10. Which factor primarily determines bond polarity?
- (A) Bond length
- (B) Electronegativity difference
- (C) Atomic radii
- (D) Molecular symmetry
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Correct Answer: (B) Electronegativity difference
Explanation: Bond polarity arises from unequal electron sharing due to differences in atoms' electronegativity values.11. Which statement about interstitial alloys is correct?
- (A) Components have similar atomic radii
- (B) Exhibit greater malleability than pure metals
- (C) Smaller atoms occupy spaces in metal lattice
- (D) Bronze is a common example
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Correct Answer: (C) Smaller atoms occupy spaces in metal lattice
Explanation: Interstitial alloys form when small atoms (e.g., C, B) fit into interstices of a host metal lattice, increasing rigidity.12. For which compound would lattice energy calculations follow Coulomb's law most accurately?
- (A) CO₂
- (B) CH₄
- (C) MgO
- (D) SiO₂
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Correct Answer: (C) MgO
Explanation: Coulomb's law (E ∝ q₁q₂/r) applies best to ionic compounds like MgO with complete electron transfer.13. Which substance demonstrates both covalent network bonding and electrical conductivity?
- (A) Diamond
- (B) Sodium chloride
- (C) Graphite
- (D) Ice
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Correct Answer: (C) Graphite
Explanation: Graphite's sp² hybridized layers contain delocalized electrons that allow conductivity, unlike diamond's sp³ network.14. What is the bond order of the C-O bond in carbonate ion (CO₃²⁻) considering resonance?
- (A) 1.0
- (B) 1.33
- (C) 1.5
- (D) 2.0
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Correct Answer: (B) 1.33
Explanation: Resonance gives 4 bonds distributed over 3 O-atoms: (1 double + 2 singles)/3 = 4/3 ≈ 1.33 bond order.15. Which molecular geometry results from sp³d hybridization?
- (A) Linear
- (B) Trigonal planar
- (C) Tetrahedral
- (D) Trigonal bipyramidal
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Correct Answer: (D) Trigonal bipyramidal
Explanation: sp³d hybridization corresponds to 5 electron domains, producing trigonal bipyramidal geometry (e.g., PCl₅).16. Which factor primarily explains why LiF has higher lattice energy than NaCl?
- (A) Smaller ionic radius of Li⁺
- (B) Greater charge on Na⁺
- (C) Higher electronegativity of Cl
- (D) Covalent character in NaCl
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Correct Answer: (A) Smaller ionic radius of Li⁺
Explanation: According to Coulomb's law, smaller ions (Li⁺ = 76 pm vs Na⁺ = 102 pm) decrease distance (r), increasing lattice energy.17. In the formate ion (HCOO⁻), what is the formal charge on the single-bonded oxygen?
Structure: H-C(=O)-O⁻ (resonance exists)
- (A) -1
- (B) 0
- (C) +1
- (D) -2
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Correct Answer: (A) -1
Explanation: For single-bonded O: FC = 6 - (6 + 2/2) = 6 - (6 + 1) = -1 (6 valence e⁻, 6 lone e⁻, 1 bond).18. Which substance violates the "like dissolves like" principle with water?
- (A) Methanol (CH₃OH)
- (B) Ammonia (NH₃)
- (C) Silicon dioxide (SiO₂)
- (D) Hydrochloric acid (HCl)
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Correct Answer: (C) Silicon dioxide (SiO₂)
Explanation: SiO₂ is network covalent with no polarity, insoluble in polar water despite water's ability to dissolve ionic/polar substances.19. What is the electron domain geometry for a molecule with 2 bonding pairs and 1 lone pair?
- (A) Linear
- (B) Trigonal planar
- (C) Bent
- (D) Tetrahedral
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Correct Answer: (B) Trigonal planar
Explanation: 3 electron domains (2 bonds + 1 lone pair) arrange in trigonal planar geometry (e.g., SO₂).20. Which comparison of bond lengths is correct?
- (A) C≡C < C=C
- (B) N-N > N≡N
- (C) C-C < C=C
- (D) O=O > O-O
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Correct Answer: (A) C≡C < C=C
Explanation: Triple bonds are shorter than double bonds due to greater electron density between nuclei (C≡C: 120 pm, C=C: 134 pm).21. Which substance is most likely to conduct electricity when dissolved in water?
- (A) CH₃OH
- (B) SiO₂
- (C) NH₄NO₃
- (D) C₆H₁₂O₆
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Correct Answer: (C) NH₄NO₃
Explanation: Ionic compounds like ammonium nitrate dissociate into ions in water, enabling electrical conductivity.22. What is the molecular geometry of XeF₄?
- (A) Tetrahedral
- (B) Square planar
- (C) Trigonal bipyramidal
- (D) Octahedral
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Correct Answer: (B) Square planar
Explanation: XeF₄ has 6 electron domains (4 bonds + 2 lone pairs), resulting in square planar molecular geometry.23. Which factor decreases lattice energy for ionic compounds?
- (A) Higher ion charges
- (B) Smaller ionic radii
- (C) Increased atomic mass
- (D) Larger interionic distance
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Correct Answer: (D) Larger interionic distance
Explanation: Lattice energy ∝ q₁q₂/r, so increased distance between ions decreases lattice energy.24. Which molecule has a permanent dipole moment?
- (A) CO₂
- (B) BF₃
- (C) CHCl₃
- (D) CCl₄
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Correct Answer: (C) CHCl₃
Explanation: Chloroform has polar C-Cl bonds and asymmetric tetrahedral structure, creating net dipole moment.25. What hybridization occurs in the carbon atoms of C₂H₂?
- (A) sp
- (B) sp²
- (C) sp³
- (D) sp³d
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Correct Answer: (A) sp
Explanation: Acetylene (C₂H₂) has triple bonds with 180° bond angles, characteristic of sp hybridization.26. Why are ionic compounds brittle?
- (A) Free electron movement
- (B) Delocalized π electrons
- (C) Repulsion of like charges when layers shift
- (D) Weak intermolecular forces
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Correct Answer: (C) Repulsion of like charges when layers shift
Explanation: When ionic crystal layers shift, ions of like charge align and repel, causing fracture.27. Which represents the correct Lewis structure for phosphate ion (PO₄³⁻)?
- (A) Four single P-O bonds
- (B) Three single P-O bonds and one P=O bond
- (C) Two single P-O bonds and two P=O bonds
- (D) Resonance of four equivalent P-O bonds
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Correct Answer: (D) Resonance of four equivalent P-O bonds
Explanation: PO₄³⁻ exhibits resonance with four identical P-O bonds (bond order 1.25), not distinct single/double bonds.28. How does bond energy correlate with bond order?
- (A) Higher bond order decreases bond energy
- (B) Bond order has no effect on bond energy
- (C) Higher bond order increases bond energy
- (D) Bond energy depends only on atomic size
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Correct Answer: (C) Higher bond order increases bond energy
Explanation: Greater bond order indicates more shared electrons and stronger bonds (C≡C > C=C > C-C).29. Which element can form compounds with expanded octets?
- (A) Nitrogen
- (B) Carbon
- (C) Sulfur
- (D) Oxygen
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Correct Answer: (C) Sulfur
Explanation: Period 3+ elements like sulfur have d-orbitals available for expanded octets (e.g., SF₆).30. Which comparison of metallic bonds is correct?
- (A) Li < K (bond strength)
- (B) Na > Mg (bond strength)
- (C) Al < Na (malleability)
- (D) Fe > Au (ductility)
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Correct Answer: (B) Na > Mg (bond strength)
Explanation: Mg has stronger metallic bonds than Na due to higher charge density (Mg²⁺ vs Na⁺).31. Which substance has the highest melting point?
- (A) Sodium chloride (NaCl)
- (B) Carbon dioxide (CO₂)
- (C) Silicon dioxide (SiO₂)
- (D) Methane (CH₄)
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Correct Answer: (C) Silicon dioxide (SiO₂)
Explanation: Network covalent solids like SiO₂ have extremely high melting points due to extensive covalent bonding throughout the crystal lattice.32. Which statement about graphite is correct?
- (A) It consists of sp³ hybridized carbon atoms
- (B) It has a tetrahedral molecular geometry
- (C) Delocalized electrons between layers enable conductivity
- (D) It's harder than diamond
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Correct Answer: (C) Delocalized electrons between layers enable conductivity
Explanation: Graphite's conductivity comes from delocalized π electrons in its sp² hybridized layered structure.33. What is the electron domain geometry for ICl₃?
- (A) Trigonal planar
- (B) T-shaped
- (C) Trigonal bipyramidal
- (D) Tetrahedral
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Correct Answer: (C) Trigonal bipyramidal
Explanation: ICl₃ has 5 electron domains (3 bonds + 2 lone pairs), resulting in trigonal bipyramidal electron geometry.34. Which factor increases the covalent character of an ionic bond?
- (A) Larger cation size
- (B) Smaller anion size
- (C) Higher charge density of ions
- (D) Greater difference in electronegativity
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Correct Answer: (C) Higher charge density of ions
Explanation: High charge density (small size + high charge) leads to polarization and increased covalent character (Fajans' rules).35. What is the hybridization of sulfur in SO₄²⁻?
- (A) sp
- (B) sp²
- (C) sp³
- (D) sp³d
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Correct Answer: (C) sp³
Explanation: SO₄²⁻ has tetrahedral geometry with 109.5° bond angles, indicating sp³ hybridization.36. Which compound has bonds with the greatest ionic character?
- (A) CsF
- (B) NaF
- (C) MgO
- (D) AlCl₃
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Correct Answer: (C) MgO
Explanation: MgO has the highest ionic character due to large electronegativity difference (ΔEN = 2.13) and high ion charges.37. Which statement about metallic bonding is correct?
- (A) Bond strength decreases with increasing valence electrons
- (B) Transition metals have weaker bonds than alkali metals
- (C) Malleability results from mobile ions
- (D) Electron sea model explains electrical conductivity
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Correct Answer: (D) Electron sea model explains electrical conductivity
Explanation: Delocalized electrons in the "electron sea" can move freely, enabling conductivity in metallic bonds.38. Which molecule has a trigonal pyramidal molecular geometry?
- (A) BF₃
- (B) CH₄
- (C) NH₃
- (D) H₂O
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Correct Answer: (C) NH₃
Explanation: Ammonia has 4 electron domains (3 bonds + 1 lone pair) resulting in trigonal pyramidal molecular geometry.39. What is the bond angle in a molecule with sp² hybridization?
- (A) 90°
- (B) 109.5°
- (C) 120°
- (D) 180°
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Correct Answer: (C) 120°
Explanation: sp² hybridization produces trigonal planar geometry with 120° bond angles (e.g., BF₃).40. Which substance is an example of a substitutional alloy?
- (A) Steel (Fe with C)
- (B) Brass (Cu with Zn)
- (C) Bronze (Cu with Sn)
- (D) Both B and C
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Correct Answer: (D) Both B and C
Explanation: Brass and bronze are substitutional alloys where similar-sized atoms replace each other, while steel is interstitial.41. Which substance demonstrates the "like dissolves like" principle when mixed with hexane (C₆H₁₄)?
- (A) Sodium chloride (NaCl)
- (B) Ethanol (CH₃CH₂OH)
- (C) Benzene (C₆H₆)
- (D) Water (H₂O)
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Correct Answer: (C) Benzene (C₆H₆)
Explanation: Nonpolar benzene dissolves in nonpolar hexane due to similar intermolecular forces, following "like dissolves like".42. Which statement about lattice energy is correct?
- (A) NaCl has higher lattice energy than MgO
- (B) KBr has higher lattice energy than KCl
- (C) CaO has higher lattice energy than NaF
- (D) LiF has lower lattice energy than CsF
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Correct Answer: (C) CaO has higher lattice energy than NaF
Explanation: Ca²⁺ and O²⁻ have higher charges than Na⁺ and F⁻, resulting in stronger electrostatic attraction.43. Which molecule has a bond angle closest to 109.5°?
- (A) BeCl₂
- (B) BF₃
- (C) H₂O
- (D) CH₄
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Correct Answer: (D) CH₄
Explanation: Methane has perfect tetrahedral geometry with 109.5° bond angles due to sp³ hybridization.44. Why does diamond have an extremely high melting point?
- (A) Strong metallic bonds
- (B) Delocalized π electrons
- (C) Covalent network structure
- (D) Ionic lattice forces
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Correct Answer: (C) Covalent network structure
Explanation: Diamond's 3D network of strong covalent bonds requires immense energy to break.45. Which element can form compounds with incomplete octets?
- (A) Phosphorus
- (B) Sulfur
- (C) Boron
- (D) Chlorine
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Correct Answer: (C) Boron
Explanation: Boron compounds like BF₃ often have incomplete octets (6 electrons) due to its electron deficiency.46. What is the formal charge on sulfur in SF₆?
- (A) 0
- (B) +1
- (C) -1
- (D) +2
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Correct Answer: (A) 0
Explanation: Formal charge = 6 - (0 + 12/2) = 6 - 6 = 0 (6 valence e⁻, 0 lone e⁻, 6 bonds).47. Which substance is classified as a molecular solid?
- (A) Diamond
- (B) Sodium metal
- (C) Dry ice (solid CO₂)
- (D) Quartz (SiO₂)
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Correct Answer: (C) Dry ice (solid CO₂)
Explanation: Dry ice consists of discrete CO₂ molecules held by intermolecular forces, characteristic of molecular solids.48. What is the molecular geometry of ClF₃?
- (A) Trigonal planar
- (B) T-shaped
- (C) Tetrahedral
- (D) Square pyramidal
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Correct Answer: (B) T-shaped
Explanation: ClF₃ has 5 electron domains (3 bonds + 2 lone pairs), resulting in T-shaped molecular geometry.49. Which factor explains why Mg has stronger metallic bonds than Na?
- (A) Larger atomic radius
- (B) Higher nuclear charge
- (C) Fewer valence electrons
- (D) Lower melting point
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Correct Answer: (B) Higher nuclear charge
Explanation: Mg²⁺ has higher charge density than Na⁺ due to greater nuclear charge, strengthening metallic bonds.50. Which compound exhibits both ionic and covalent bonding?
- (A) CH₄
- (B) Na₂O
- (C) NH₄Cl
- (D) CO₂
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Correct Answer: (C) NH₄Cl
Explanation: Ammonium chloride contains covalent bonds within NH₄⁺ ions and ionic bonds between NH₄⁺ and Cl⁻.