Final answer:
Glycerol, having a higher viscosity than water at 25 degrees Celsius, exhibits the strongest intermolecular attractions due to its larger molecular size, which allows for greater London dispersion forces, in addition to hydrogen bonding.
Step-by-step explanation:
The substance with the strongest intermolecular attraction is indicated by its viscosity at a given temperature. In this case, at 25 degrees Celsius, glycerol is more viscous than water, suggesting that glycerol has stronger intermolecular forces. While water has a molar mass of 18.01 g/mol and engages in extensive hydrogen bonding, its smaller size results in weaker dispersion forces compared to larger molecules that can exhibit more substantial London dispersion forces.
Glycerol, with a molar mass of 92.09 g/mol, also has the capability for hydrogen bonding due to its multiple -OH groups. In addition to hydrogen bonding, its larger molecular size compared to water results in greater London dispersion forces, contributing to the overall stronger intermolecular attractions in glycerol. This combination of factors means that glycerol molecules will have a greater resistance to flow (viscosity) and also a lower vapor pressure due to less tendency for the molecules to escape into the vapor phase.