WAEC Chemistry 2017 Paper

Concept:Tetrahedral molecules have a fixed bond angle due to equal repulsion between bonding electron pairs.Explanation:In tetrachloromethane, $\mathrm{CCl}_4$, the central carbon atom is bonded to four chlorine atoms.These four bonding pairs of electrons repel one another equally.To minimise repulsion, the pairs arrange themselves symmetrically in three dimensions.This symmetry produces a tetrahedral shape around the carbon atom.The measured angle between any two carbon–chlorine bonds is $109.5^\circ$.This angle is characteristic of all perfect tetrahedral molecules.Other bond angles, such as $180^\circ$, $105.5^\circ$, or $90^\circ$, belong to different molecular geometries.Answer:B. $109.5^\circ$