Chemical Bonding & Structure — Part 1: 40 MCQs with Explanations

BF₃ has trigonal planar geometry with sp² hybridization, giving bond angles of 120°.

All carbon atoms in benzene are sp² hybridized, forming trigonal planar geometry with 120° bond angles.

Acid strength increases down the group: HF < HCl < HBr < HI due to decreasing bond strength and increasing size of conjugate base.

Water exhibits extensive hydrogen bonding with each molecule capable of forming up to 4 hydrogen bonds (2 through H atoms and 2 through lone pairs), leading to its anomalously high boiling point.

Ethene (C₂H₄) has trigonal planar geometry around each carbon with bond angles ~120°, characteristic of sp² hybridization.

N₂ has triple bond: one σ bond and two π bonds.

But-2-ene (CH₃CH=CHCH₃) shows geometrical isomerism because each carbon of double bond has two different groups.

HF is weakest due to strong H-F bond and hydrogen bonding in undissociated molecules.

CH₄ has four bonding pairs with no lone pairs, giving perfect tetrahedral geometry (109.5°).

OH⁻ has lone pair to donate, making it a nucleophile.

Strong electrolytes are fully dissociated; increased molar conductivity with dilution is due to decreased interionic attraction and increased ionic mobility.

Bond lengths: C-C (154 pm), C=C (134 pm), C≡C (120 pm).

MgO has highest melting point (~2852°C) due to strong ionic bonding with high charges (+2 and -2) and small ionic sizes.

CO₂ has sp hybridization with no lone pairs on carbon, giving linear geometry (O=C=O, 180°).

Four-carbon chain with double bond between carbons 2 and 3: but-2-ene.

Lattice energy increases with decreasing ionic size. Li⁺ is smallest alkali metal ion, so LiF has highest lattice energy.

Four-carbon chain with triple bond between carbons 2 and 3: but-2-yne or 2-butyne.

NH₃ has trigonal pyramidal geometry with bond angle 107° (less than tetrahedral 109.5° due to lone pair repulsion).

CrO₅ has one Cr=O bond and two peroxide linkages (O-O). Each peroxide O has -1 oxidation state. x + (-2) + 4(-1) = 0 → x = +6.

CH₃Cl has highest dipole moment (~1.9 D) as vector sum of bond moments is maximum for single polar bond in tetrahedral geometry.

Ethene has 4 C-H sigma bonds and 1 C-C sigma bond (the double bond consists of 1 sigma and 1 pi bond), totaling 5 sigma bonds.

Ethene (C₂H₄) has trigonal planar geometry around each carbon with bond angles ~120°, characteristic of sp² hybridization.

CH₃CH=CHCH₃ (but-2-ene) shows cis-trans isomerism because each carbon of the double bond has two different groups attached.

HF is the weakest acid among hydrogen halides due to strong H-F bond and high stability of undissociated HF molecules (hydrogen bonding).

CH₄ has four bonding pairs with no lone pairs, giving perfect tetrahedral geometry (109.5°). NH₃ is trigonal pyramidal, H₂O is bent, BF₃ is trigonal planar.

For strong electrolytes (fully dissociated), equivalent conductance increases with dilution primarily due to increased ionic mobility (decreased interionic attraction), not increased dissociation.

Bond length decreases with increasing bond order: C-C (154 pm) > C=C (134 pm) > C≡C (120 pm). C-H bond (~109 pm) is shorter than C-C but longer than C≡C.

NaCl has the highest melting point due to strong ionic bonding in a giant ionic lattice. MgCl₂ also ionic but with some covalent character. AlCl₃ and SiCl₄ are covalent molecular compounds with low melting points.

CH₃CH₂COOH (propanoic acid) has highest solubility due to strong hydrogen bonding with water and ionic character of carboxylate group in solution.

CO₂ has sp hybridization with no lone pairs on carbon, giving linear geometry (O=C=O, 180°). H₂O is bent, NH₃ is trigonal pyramidal, SO₂ is bent.

Four-carbon chain with double bond starting at carbon 1: but-1-ene.

Lattice energy increases with decreasing ionic size. F⁻ is smallest halide ion, so NaF has highest lattice energy.

Four-carbon chain with triple bond starting at carbon 1: but-1-yne.

Ammonia has trigonal pyramidal geometry with bond angle 107° (less than tetrahedral 109.5° due to lone pair-bond pair repulsion).

CrO₅ (chromium pentoxide) has one Cr=O double bond and two peroxide linkages (O-O). Each peroxide oxygen has -1 oxidation state. Let Cr oxidation state = x: x + 1(-2) + 4(-1) = 0 → x - 2 - 4 = 0 → x = +6.

CH₃Cl has the highest dipole moment (~1.9 D) among these chloromethanes. Although CH₂Cl₂ has two C-Cl bonds, their vector sum is less than the single C-Cl bond moment in CH₃Cl due to geometry.

Lactose is a reducing sugar because it has a free anomeric carbon in its glucose unit. Sucrose is non-reducing (both anomeric carbons involved in glycosidic bond). Starch and cellulose are polysaccharides with mostly non-reducing ends.

In ice, water molecules are held together in a crystalline lattice primarily by hydrogen bonds, which are strong intermolecular forces.

Molecular solids are held together by intermolecular forces. Iodine (I2) crystals are held by weak London dispersion forces. NaCl is ionic, while diamond and SiC are network covalent solids.

Ionic solids (e.g., NaCl) are characterized by a three-dimensional lattice of positive and negative ions held together by strong electrostatic forces (ionic bonds).