Chemical Bonding & Structure — Part 2: 15 MCQs with Explanations

Alkenes like ethene (C2H4) have a double bond that undergoes an addition reaction with bromine water, decolorizing it from reddish-brown to colorless. Alkanes and benzene (under normal conditions) do not react.

According to VSEPR theory, the central O atom in H₂O has two bond pairs and two lone pairs. The lone pairs repel more strongly, compressing the bond angle from the ideal tetrahedral angle (109.5°) to about 104.5°.

Strong electrolytes are substances that completely dissociate into ions in solution. NaCl is an ionic compound that dissociates completely into Na⁺ and Cl⁻ ions in water.

CO₂ has a linear structure due to sp hybridization of the carbon atom. The molecule is O=C=O, with a bond angle of 180°.

Hydrogen bonding is maximum in water because each water molecule can form up to four hydrogen bonds with neighboring water molecules (two through its H atoms and two through its lone pairs on oxygen).

Vapor pressure depends on intermolecular forces. Diethyl ether has weak dipole-dipole interactions and no hydrogen bonding, so it evaporates easily and has a high vapor pressure at room temperature.

Geometrical isomerism occurs in compounds with restricted rotation, such as alkenes. 1,2-dichloroethene (C₂H₂Cl₂) exists as cis and trans isomers due to the double bond.

London dispersion forces (induced dipole-induced dipole interactions) are the weakest intermolecular forces. They are temporary and exist in all molecules, especially nonpolar ones.

According to VSEPR theory, an AB₄ type molecule with no lone pairs on the central atom (e.g., CH₄) has a tetrahedral geometry with bond angles of approximately 109.5°.

Baeyer's test (using cold, dilute, alkaline KMnO₄) is used to test for unsaturation. The purple color of KMnO₄ is discharged as it reacts with the double or triple bond, forming a colorless diol or other products.

CO₂ has sp hybridization with bond angle 180°. H₂O (bent, 104.5°), NH₃ (trigonal pyramidal, 107°), CH₄ (tetrahedral, 109.5°).

Covalent network solids (diamond, SiO₂) have strong directional covalent bonds throughout lattice, giving very high melting points.

Bond dissociation energy is energy required to break one mole of bonds in gaseous state.

Carbon shows maximum catenation (self-linking ability) due to strong C-C bonds and tetravalency, forming long chains and rings.

Denaturation disrupts secondary/tertiary structure (H-bonds, hydrophobic interactions) but not primary structure (peptide bonds remain intact).