WAEC Chemistry 2024 Paper

Concept:Boiling point depends on the strength of intermolecular forces.Stronger forces lead to a higher boiling point.Explanation:Sodium chloride ($\mathrm{NaCl}$) in aqueous solution breaks into ions.This produces strong ion-dipole attractions, raising the boiling point.Water ($\mathrm{H_2O}$) and ethanol ($\mathrm{C_2H_5OH}$) both form hydrogen bonds.Hydrogen bonding is a strong intermolecular force, so they need much heat to boil.Tetrachloromethane ($\mathrm{CCl_4}$) is a nonpolar covalent molecule.Only weak London dispersion forces exist between its molecules.There is no hydrogen bonding in $\mathrm{CCl_4}$.Hence, less energy is needed to separate its molecules.So tetrachloromethane has the lowest boiling point.Answer:C. Tetrachloromethane