Hexane is a hydrocarbon (a molecule containing only carbon and hydrogen) with a molecular weight of 86.18 g/mol,
a density of 0.660 g/mL, and a boiling point of 69C .
Pentanol is an alcohol (a hydrocarbon with a "OH" group attached to one of its carbons) with a molecular weight of
88.15 g/mol, a density of 0.814 g/mL, and a boiling point of 137C .
Pentanol has the higher boiling point. Why?
A. Hydrogen bonding requires that a pentanol molecule have more energy to escape the liquid phase.
B. Pentanol is capable of hydrogen bonding, so it goes into the gas phase more easily.
C. Hexane has stronger intermolecular forces, so it boils at a lower temperature.
D. The higher molecular weight of pentanol results in a higher boiling point.
E. The dispersion forces in hexane are weaker.
----i've seen that others have posted this question and after thinking about it i thinks its c. im i right?
4 answers
B. Pentanol IS capable of hydrogen bonding (so far so good) so it makes the boiling point higher, not lower.
C. Hexane has WEAKER intermolecular forces (or said another way, pentanol, because it's an alcohol, has stronger intermolecular forces;; again, hydrogen bonding----
D. Generally it is true that higher molecular weights result in higher boiling points but we are talking about only two units here and that isn't enough to make much difference.
E. The dispersion forces in the two are more or less the same, especially, since the molar mass is about the same.
1 answer