Which of the following molecules has the lowest viscosity?

Question

1. Which of the following molecules has the lowest viscosity?

a. methanol

b. glycerol

c. methane

d. water

2. The boiling point of methane (CH4) is much lower than that of hydrogen fluoride (HF) because? 



a. CH4 is more polar

b. of hydrogen bonding in HF

c. of ion-dipole interactions in CH4

d. of dipole-dipole interactions in CH4

Answer 1

1). Well, viscosity will change with temperature (and pressure), so maybe this question isn't exactly fair since at STP, methane (c) is a gas and wouldn't really have a viscosity as related to that of liquids. So, I'd choose this as the answer. If you neglect gases, then the next lowest viscosity would be methanol as it would have the weakest intermolecular forces among the remaining choices.

2). CH4 has a much lower b.p. than HF because the intermolecular forces in CH4 are dispersion forces and the those in HF are hydrogen bonding. Since hydrogen bonding is a much stronger force, HF will have a higher b.p. So the answer is (b).