WAEC Chemistry 2021 Paper

Concept:Hydrogen bonding occurs between molecules when hydrogen is attached to a highly electronegative atom such as oxygen, nitrogen, or fluorine.Explanation:Both $\mathrm{C_2H_5OH}$ and $\mathrm{CH_3OH}$ contain an $-\mathrm{OH}$ group.In this group, hydrogen is covalently bonded to oxygen.Oxygen is highly electronegative, so the $-\mathrm{OH}$ bond is polar.The hydrogen atom can form a hydrogen bond with the lone pair of oxygen on a neighbouring molecule.Thus, ethanol and methanol both form intermolecular hydrogen bonds.The other options lack such $-\mathrm{O}-\mathrm{H}$, $-\mathrm{N}-\mathrm{H}$, or $\mathrm{H}-\mathrm{F}$ bonds.So the correct pair is $\mathrm{C_2H_5OH}$ and $\mathrm{CH_3OH}$.Answer:A. $\mathrm{C_2H_5OH}$ and $\mathrm{CH_3OH}$