A chemist compares two pure liquids—glycerol, C3H8O3, and acetone, C3H6O—both measured at 25 °C under 1 atm. The technician reports the following observations:
• Glycerol pours much more slowly than acetone.
• The normal boiling point of glycerol is 290 °C, whereas the normal boiling point of acetone is 56 °C.
• When small beads of each liquid are placed on identical clean glass slides, the bead of glycerol maintains a nearly hemispherical shape, but the acetone bead spreads out rapidly.
Answer the following questions about the two liquids.
(a) Describe the dominant types of intermolecular forces present in each liquid and rank those forces from weakest to strongest for the two substances.
(b) Explain, in terms of the intermolecular forces you identified in part (a), why glycerol has a much higher viscosity than acetone at 25 °C.
(c) Provide a molecular-level explanation for the large difference in the normal boiling points of the two liquids.
(d) The glass slide in the experiment is polar and capable of hydrogen bonding with adsorbed water molecules. Explain why the drops of glycerol and acetone adopt the different shapes described above when placed on the slide.