Predict Boiling Points of Molecules: CH_{3}F, C_{2}H_{6}, CH_{3}OH, C_{2}H_{4}

[temaire]

Homework Statement

For the following molecules, predict the order of their boiling points from highest to lowest.

1. [tex]CH_{3}F[/tex]
2. [tex]C_{2}H_{6}[/tex]
3. [tex]CH_{3}OH[/tex]
4. [tex]C_{2}H_{4}[/tex]

The Attempt at a Solution

I think the answer is 3 4 2 1. I put 3 first because it is an alcohol and has hydrogen bonding. I put 4 second because it has a double bond. I put 2 third becuase although it has the same amount of electrons as [tex]CH_{3}F[/tex] it is a larger molecule. Am I correct?

 

[war485]

I agree that methanol has the highest boiling point. As for the other 3 choices, rethink them. Why else (besides the extra small weight) makes the alkene have a higher boiling point? Compare that to electronegativity. Which factor's more important?

 

[Blueshift5]

Your reasoning is mostly correct. The boiling point of a molecule is determined by its intermolecular forces, which are affected by factors such as molecular size, polarity, and hydrogen bonding. Based on this, the predicted order of boiling points for the given molecules would be:

1. CH3OH - This molecule has the strongest intermolecular forces due to its ability to form hydrogen bonds between the oxygen and hydrogen atoms.
2. C2H6 - Although this molecule is larger than CH3F, it does not have any polar bonds or hydrogen bonding, so its boiling point would be lower than CH3OH.
3. C2H4 - This molecule has a double bond, which creates some polarity, but it is still relatively small and does not have any hydrogen bonding, so its boiling point would be lower than CH3OH and C2H6.
4. CH3F - This molecule is the smallest and has no polar bonds or hydrogen bonding, so it would have the lowest boiling point of the four molecules.

Overall, your ranking is correct, but it is important to consider all relevant factors when predicting the boiling points of molecules.