Final answer:
Propanoic acid (CH₃CH₂COOH) has greater viscosity than methyl acetate (CH₃COOCH₃) due to its ability to form stronger hydrogen bonds.
Step-by-step explanation:
To determine which substance has greater viscosity, propanoic acid (CH₃CH₂COOH) or methyl acetate (CH₃COOCH₃), we must consider the intermolecular forces present in each substance. Propanoic acid is a carboxylic acid and is capable of forming hydrogen bonds due to the presence of both a carbonyl group (C=O) and a hydroxyl group (OH). Methyl acetate, on the other hand, is an ester and cannot form hydrogen bonds as effectively as propanoic acid because while it has a carbonyl group, it lacks the hydroxyl group for hydrogen bonding. Therefore, propanoic acid will have stronger intermolecular attractions and consequently, a higher viscosity compared to methyl acetate.