2021 O Level Chem P1 Q7 — Covalent Bonding Solution

Answer: C (1 and 3). A single covalent bond is one shared pair of electrons.

Ammonia, NH₃ (1), has three N–H single bonds only ✓. Carbon dioxide, CO₂ (2), has two C=O double bonds, so it contains multiple bonds ✗. Ethanol, C₂H₅OH (3), contains only C–C, C–H, C–O and O–H single bonds ✓.

So only ammonia and ethanol contain only single covalent bonds — statements 1 and 3. The trap is carbon dioxide, whose double bonds are easy to forget.