Unit 2: Chemical Bonding — MCQ Set
Question 1:
Which statement best explains why metals conduct electricity?
- (A) Electrons are localized in fixed covalent bonds.
- (B) Ions move freely in the solid lattice.
- (C) A sea of delocalized valence electrons moves through the lattice.
- (D) Protons carry charge through metallic crystals.
View Answer
Correct Answer: (C)
Explanation: Metallic bonding features mobile, delocalized electrons that can carry charge.
Question 2:
Which metal exhibits stronger metallic bonding under standard conditions?
- (A) Li
- (B) Mg
- (C) Both equal
- (D) Neither shows metallic bonding
View Answer
Correct Answer: (B) Mg
Explanation: Mg contributes two valence electrons to the electron sea, strengthening metallic bonding compared to Li (one).
Question 3:
Which statement about alloys is correct?
- (A) Interstitial alloys form when similar-sized atoms substitute into the lattice.
- (B) Substitutional alloys place small atoms in lattice holes, increasing rigidity.
- (C) Interstitial alloys place small atoms in lattice holes; substitutional alloys replace host atoms with comparable-radius atoms.
- (D) Only substitutional alloys exist for metals.
View Answer
Correct Answer: (C)
Explanation: Interstitial = small atoms in gaps (often harder); substitutional = similar-size atoms replace host sites (often still malleable/ductile).
Question 4:
Which trend gives the largest lattice energy for an ionic solid?
- (A) Lower ionic charges and larger radii
- (B) Higher ionic charges and smaller radii
- (C) Higher ionic charges and larger radii
- (D) Lower ionic charges and smaller radii
View Answer
Correct Answer: (B)
Explanation: Coulombic attraction increases with |q1q2| and decreases with distance.
Question 5:
Which correctly represents the conventional lattice energy process?
- (A) X(g) + Y(g) → XY(s)
- (B) XY(s) → X+(g) + Y-(g)
- (C) X+(aq) + Y-(aq) → XY(s)
- (D) XY(l) → X+(g) + Y-(g)
View Answer
Correct Answer: (B)
Explanation: Lattice energy is defined for separating one mole of an ionic solid into its gaseous ions.
Question 6:
Which compound has the greatest lattice energy?
- (A) NaCl
- (B) LiF
- (C) MgO
- (D) KBr
View Answer
Correct Answer: (C) MgO
Explanation: 2+ / 2− charges and relatively small ionic radii maximize Coulombic attraction.
Question 7:
Which salt is predicted to be always soluble in water based on common rules?
- (A) NaNO3
- (B) AgCl
- (C) BaSO4
- (D) CaCO3
View Answer
Correct Answer: (A) NaNO3
Explanation: All Group 1 and nitrate (NO3-) salts are soluble.
Question 8:
Which pair are allotropes of the same element?
- (A) Diamond and graphite
- (B) 12C and 13C
- (C) Ethanol and dimethyl ether
- (D) CO and CO2
View Answer
Correct Answer: (A)
Explanation: Allotropes are different structural forms of the same element (both are carbon).
Question 9:
Which pair are isotopes?
- (A) 12C and 13C
- (B) Diamond and graphite
- (C) H2O and D2O
- (D) CH3CH2OH and CH3OCH3
View Answer
Correct Answer: (A)
Explanation: Isotopes = same element, different mass numbers.
Question 10:
Which pair are constitutional isomers?
- (A) CO and CO2
- (B) CH3CH2OH and CH3OCH3
- (C) 35Cl and 37Cl
- (D) Diamond and graphite
View Answer
Correct Answer: (B)
Explanation: Same formula C2H6O, different connectivity (ethanol vs dimethyl ether).
Question 11:
Which substance conducts electricity in the solid state?
- (A) NaCl
- (B) Ice
- (C) Graphite
- (D) Diamond
View Answer
Correct Answer: (C) Graphite
Explanation: Delocalized electrons within layers allow conduction.
Question 12:
Which liquid has the lowest normal boiling point among the following?
- (A) H2O
- (B) NH3
- (C) CH4
- (D) HF
View Answer
Correct Answer: (C) CH4
Explanation: Nonpolar; only London dispersion forces.
Question 13:
Which statement about bond order, bond length, and bond energy (same atom pair) is correct?
- (A) Higher bond order → longer bond length → higher bond energy
- (B) Higher bond order → shorter bond length → higher bond energy
- (C) Higher bond order → shorter bond length → lower bond energy
- (D) Bond order is unrelated to length and energy
View Answer
Correct Answer: (B)
Explanation: Single > double > triple in length; triple > double > single in energy.
Question 14:
Which statement about resonance is accurate?
- (A) Resonance structures rapidly interconvert in equilibrium.
- (B) The actual structure is a hybrid; equivalent bonds often have averaged length/strength.
- (C) Resonance requires breaking sigma bonds each instant.
- (D) Resonance only occurs in nonpolar molecules.
View Answer
Correct Answer: (B)
Explanation: Resonance is delocalization of electrons; the real molecule is a weighted hybrid, not a dynamic flip.
Question 15:
What is the formal charge on nitrogen in NH4+?
- (A) −1
- (B) 0
- (C) +1
- (D) +2
View Answer
Correct Answer: (C) +1
Explanation: FC = 5 − (0 lone e- + 4 bonds) = +1.
Question 16:
Which rule is best for choosing the most important Lewis structure among alternatives?
- (A) Maximize formal charges on central atoms.
- (B) Prefer structures with formal charges as close to zero as possible and negative charges on more electronegative atoms.
- (C) Place negative charges on electropositive atoms.
- (D) Always give the central atom a positive formal charge.
View Answer
Correct Answer: (B)
Explanation: Minimal formal charge separation and proper placement improve stability.
Question 17:
Which pair has the same electron-domain geometry but different molecular geometry?
- (A) CO2 and SO2
- (B) CH4 and NH3
- (C) BF3 and CO32−
- (D) BeCl2 and H2O
View Answer
Correct Answer: (B)
Explanation: Both have tetrahedral electron-domain geometry; CH4 is tetrahedral, NH3 is trigonal pyramidal (one lone pair).
Question 18:
Which central atom is sp2-hybridized?
- (A) C in CO2
- (B) B in BF3
- (C) C in CH4
- (D) N in NH3
View Answer
Correct Answer: (B) B in BF3
Explanation: Trigonal planar geometry corresponds to sp2 hybridization.
Question 19:
At the equilibrium bond length on a potential energy curve for a diatomic molecule, which statement is true?
- (A) Repulsions are zero and attractions are maximal.
- (B) The net force is zero; the potential energy is at a minimum.
- (C) The molecule is unstable and will dissociate spontaneously.
- (D) The potential energy is maximal.
View Answer
Correct Answer: (B)
Explanation: Attractive and repulsive forces balance; the PE well minimum defines bond length.
Question 20:
Which molecule is nonpolar overall despite having polar bonds?
- (A) H2O
- (B) CO2
- (C) NH3
- (D) SO2
View Answer
Correct Answer: (B) CO2
Explanation: Linear geometry makes dipoles cancel.
Question 21:
Which statement links metallic behavior with ionization energy and ionic behavior with electron affinity?
- (A) Metals have high ionization energies; nonmetals have low electron affinities.
- (B) Metals have low ionization energies (form cations easily); nonmetals have high electron affinities (gain electrons to form anions).
- (C) Both metals and nonmetals have low ionization energies.
- (D) Electron affinity is irrelevant to ionic bonding.
View Answer
Correct Answer: (B)
Explanation: Low IE facilitates electron loss (cations); high EA favors electron gain (anions).
Question 22:
Which aqueous solution will best conduct electricity?
- (A) 0.10 M C12H22O11 (sucrose)
- (B) 0.10 M CH3OH (methanol)
- (C) 0.10 M HCl
- (D) Pure H2O
View Answer
Correct Answer: (C) 0.10 M HCl
Explanation: Strong acid fully ionizes, producing mobile ions (electrolyte).
Question 23:
Which statement about network covalent solids vs molecular solids is correct?
- (A) Network solids have lower melting points than molecular solids.
- (B) Network solids are held by extensive covalent bonding, giving very high melting points.
- (C) Molecular solids conduct electricity better than graphite.
- (D) Network solids are composed of discrete molecules held by hydrogen bonds.
View Answer
Correct Answer: (B)
Explanation: Continuous covalent networks (e.g., diamond, SiO2) are very hard with high Tm.
Question 24:
Which statement about VSEPR repulsions is correct?
- (A) Bond–bond repulsion > lone pair–bond repulsion > lone pair–lone pair
- (B) Lone pair–lone pair > lone pair–bond > bond–bond
- (C) Lone pairs have no effect on bond angles.
- (D) All repulsions are equal in magnitude.
View Answer
Correct Answer: (B)
Explanation: Lone pair domains occupy more space, compressing bond angles.
Question 25:
Which central atom is sp-hybridized?
- (A) C in H–C≡N
- (B) N in NH3
- (C) S in SO2
- (D) C in CH4
View Answer
Correct Answer: (A) C in H–C≡N
Explanation: Linear domain arrangement (two regions) → sp hybridization.
Question 26:
Which species can have an expanded octet on the central atom?
- (A) CF4
- (B) BF3
- (C) SF6
- (D) NH3
View Answer
Correct Answer: (C) SF6
Explanation: Third-period and heavier elements (like S) can exceed an octet.
Question 27:
Which substance most strongly exhibits intermolecular hydrogen bonding in the pure liquid?
- (A) CH3COOCH3 (methyl acetate)
- (B) CH3COOH (acetic acid)
- (C) CH2=CH2 (ethylene)
- (D) CCl4
View Answer
Correct Answer: (B) CH3COOH
Explanation: O–H groups both donate and accept H-bonds; acetic acid forms strong H-bonded dimers.
Question 28:
Which solvent best dissolves iodine, I2?
- (A) H2O
- (B) CH3OH
- (C) CCl4
- (D) NaCl(aq)
View Answer
Correct Answer: (C) CCl4
Explanation: “Like dissolves like”—nonpolar I2 dissolves best in nonpolar CCl4.
Question 29:
What is the dominant intermolecular force between molecules of CH3COOCH3 (methyl acetate)?
- (A) London dispersion only
- (B) Dipole–dipole interactions
- (C) Hydrogen bonding (as donor)
- (D) Ionic interactions
View Answer
Correct Answer: (B)
Explanation: The ester is polar; it lacks an O–H or N–H donor for strong H-bonding.
Question 30:
Which has the shortest C–O bond?
- (A) CH3OH
- (B) CO
- (C) CO32−
- (D) CO2
View Answer
Correct Answer: (B) CO
Explanation: CO has a C≡O triple bond (very short). Carbonate has resonance-averaged bonds longer than C=O.
Question 31:
How many equivalent resonance contributors does NO3− have (ignoring minor forms)?
- (A) 2
- (B) 3
- (C) 4
- (D) 6
View Answer
Correct Answer: (B) 3
Explanation: The double bond can be placed to any one of the three O atoms.
Question 32:
Which statement about SO42− (sulfate) is most accurate at the AP level?
- (A) It has one S=O and three S–O single bonds (all different lengths).
- (B) All four S–O bonds are equivalent due to resonance; S can expand its octet.
- (C) It has only single S–O bonds and no resonance.
- (D) It has four isolated double bonds to oxygen simultaneously.
View Answer
Correct Answer: (B)
Explanation: Resonance delocalizes π density, making S–O bonds equivalent; third-period S can exceed an octet.
Question 33:
What is the formal charge on the carbon atom in CO2 (O=C=O) using the standard Lewis structure?
- (A) −2
- (B) −1
- (C) 0
- (D) +2
View Answer
Correct Answer: (C) 0
Explanation: FC(C) = 4 − (0 lone e− + 4 bonds) = 0.
Question 34:
Which statement about acetate, CH3COO−, is correct?
- (A) Both C–O bonds are different: one single, one double only.
- (B) The negative charge is localized on one oxygen.
- (C) The carboxylate carbon is sp2 and planar; the two C–O bonds are equal by resonance.
- (D) The methyl carbon is sp2-hybridized.
View Answer
Correct Answer: (C)
Explanation: The carboxylate group is delocalized; methyl carbon is sp3.
Question 35:
Which liquid is expected to have the highest vapor pressure at the same temperature?
- (A) H2O
- (B) CH3OH
- (C) NH3
- (D) CCl4
View Answer
Correct Answer: (D) CCl4
Explanation: Weaker IMFs (nonpolar, mainly dispersion) → higher vapor pressure.
Question 36:
Which molecule has T-shaped molecular geometry (AX3E2)?
- (A) PF5
- (B) ClF3
- (C) SF6
- (D) XeF4
View Answer
Correct Answer: (B) ClF3
Explanation: 5 domains (sp3d): 3 bonds + 2 lone pairs → T-shaped.
Question 37:
Which process is exothermic?
- (A) Breaking the O–H bond in water
- (B) Dissociating Cl2 to 2 Cl(g)
- (C) Forming H–H from 2 H(g)
- (D) Subliming CO2(s) to CO2(g)
View Answer
Correct Answer: (C)
Explanation: Bond formation releases energy; bond breaking and phase separation require energy.
Question 38:
Why are ionic solids brittle?
- (A) Layers can slide easily due to delocalized electrons.
- (B) Shifting a plane aligns like charges, causing strong repulsion and fracture.
- (C) They contain discrete neutral molecules.
- (D) They have metallic bonding that breaks readily.
View Answer
Correct Answer: (B)
Explanation: Displacement can bring like charges together → repulsion → shattering.
Question 39:
Which central atom is sp3d-hybridized?
- (A) P in PF5
- (B) S in SO2
- (C) C in CO2
- (D) N in NH3
View Answer
Correct Answer: (A) P in PF5
Explanation: 5 electron domains → trigonal bipyramidal → sp3d.
Question 40:
Which sample will conduct electricity well?
- (A) Solid NaCl at 25 °C
- (B) Molten NaCl
- (C) Solid sucrose
- (D) Solid SiO2 (quartz)
View Answer
Correct Answer: (B) Molten NaCl
Explanation: Ions are mobile in the liquid; in the solid they are fixed.
Question 41:
Which statement about BF3 is correct?
- (A) It is tetrahedral and sp3.
- (B) It is trigonal planar, sp2, and a Lewis acid (electron-deficient).
- (C) It is linear, sp, and a strong base.
- (D) It contains a central boron with an octet and negative formal charge.
View Answer
Correct Answer: (B)
Explanation: Boron has 6 valence electrons in BF3, accepting electron pairs → Lewis acid.
Question 42:
Which has the highest normal boiling point?
- (A) NH3
- (B) HF
- (C) H2O
- (D) HCl
View Answer
Correct Answer: (C) H2O
Explanation: Extensive H-bond network and two H-bond donors per molecule raise boiling point.
Question 43:
Which molecule is linear due to three lone pairs occupying equatorial positions in a trigonal bipyramidal arrangement?
- (A) XeF2
- (B) SF4
- (C) PF5
- (D) ClF3
View Answer
Correct Answer: (A) XeF2
Explanation: AX2E3 (sp3d) → linear molecular geometry.
Question 44:
Which molecule has the largest dipole moment?
- (A) CF4
- (B) CH3F
- (C) CHF3
- (D) CH2F2
View Answer
Suggested Answer: (B) CH3F
Explanation: In tetrahedral geometries, vector addition often yields the largest net dipole for the single-F case; CF4 is nonpolar.
Question 45:
Which pair best illustrates “like dissolves like” for significant solubility?
- (A) NaCl in hexane
- (B) I2 in CCl4
- (C) CCl4 in water
- (D) CH3OH in hexane
View Answer
Correct Answer: (B)
Explanation: Nonpolar solute dissolves in nonpolar solvent.
Question 46:
Which bond has the greatest bond energy among typical diatomic bonds?
- (A) O=O
- (B) N≡N
- (C) H–H
- (D) Cl–Cl
View Answer
Correct Answer: (B) N≡N
Explanation: Triple bond with very high bond energy in N2.
Question 47:
Which cannot expand its valence shell beyond an octet in stable compounds?
- (A) P
- (B) S
- (C) Cl
- (D) N
View Answer
Correct Answer: (D) N
Explanation: Second-period elements (C, N, O, F) lack accessible d orbitals; no expanded octet.
Question 48:
Which statement about resonance and bond order in CO32− is correct?
- (A) One C–O is double and fixed; the others are single and fixed.
- (B) All C–O bonds are equivalent with bond order between 1 and 2.
- (C) All C–O bonds are triple bonds.
- (D) Resonance structures represent actual rapid oscillation between single, double, and triple bonds.
View Answer
Correct Answer: (B)
Explanation: The real structure is a resonance hybrid with delocalized π electrons.
Question 49:
Which statement about benzene, C6H6, is correct?
- (A) It has three fixed C=C double bonds and three fixed C–C single bonds.
- (B) All C–C bonds are equivalent due to π electron delocalization.
- (C) It is a linear molecule with alternating bonds.
- (D) It contains localized π bonds only on every other carbon.
View Answer
Correct Answer: (B)
Explanation: Aromatic resonance makes all ring C–C bonds equal in length/strength.
Question 50:
Which statement about CH3COO− (acetate) best reflects resonance effects on structure?
- (A) One C–O bond is much shorter than the other.
- (B) Both C–O bonds are equal and shorter than a typical C–O single bond.
- (C) Both C–O bonds are equal and longer than a typical C=O double bond.
- (D) (B) and (C) together describe the resonance average (between single and double).
View Answer
Best Answer: (D)
Explanation: Resonance equalizes the C–O bonds at an intermediate length: shorter than single, longer than double.