3F.19

[Cassidy Kohlenberger 3D]

In question 3F.19 in the textbook, part b asks you to explain why the vapor pressure of diethyl ether (C2H5OC2H5) is greater than that of water. What is the correlation between vapor pressure and boiling point? Also, in part c, it asks you to explain why the boiling point of pentane, CH3(CH2)3CH3, is 36.1 degrees Celsius, whereas that of 2,2-dimethylpropane (also known as neopentane), C(CH3)4, is 9.5 degrees Celsius. I know this has something to do with pentane being linear, but I don't understand why being linear correlates to a higher boiling point. Can someone explain these parts of the question?

[John Liang 2I]

You can think of vapor pressure as the opposite of boiling point. Vapor pressure is how much gas exists alongside a liquid amount of a substance. Substances with a stronger imf lead to a higher boiling point and lower vapor pressure (molecules are more attracted and less likely to evaporate).

[John Liang 2I]

Pentene being linear-shaped allows the pentene molecules to fit closer together and have a shorter distance between each other, while neopentene being spherical-shaped increases the distance between the atoms. A shorter radius between atoms leads to stronger attraction and higher boiling point. Hope this helps!