Boiling point and connection distance of the elements

[José Ricardo]

Homework Statement

Explain the following order of the boiling point (° C)

HF (19.5)> HCl (-85.1) <HBr (-66.8) <HI (-35.4)

b) Explain the following order of connection distance (pm):

HF (92) <HCl (127) <HBr (141) <HI (161)

Homework Equations

xxx

The Attempt at a Solution

a) HF does hydrogen bond, and the others make ionic linking.
b) The lower the atomic mass, the higher the boiling point

 

[baldbrain]

The lower the atomic mass, the higher the boiling point

This statement are wrong. (How?)
And the others make covalent linking, not ionic (generally means electrovalent in some texts)

HF does hydrogen bond

You mean the intermolecular one, that too in an aqueous solution

 

[baldbrain]

How does the electronegativity of the halogens & hence the H-X bond polarity change down the group?

 

[epenguin]

HF (19.5)> HCl (-85.1) <HBr (-66.8) <HI (-35.4)


b) The lower the atomic mass, the higher the boiling point

Does not constitute an explanation, nor fits the data very well!

 

[baldbrain]

Also, the statement

HF does hydrogen bond, and the others make ionic linking.

makes it a bit ambiguous to know whether you've understood the concept of hydrogen bonding

 

[José Ricardo]

This statement are wrong. (How?)
And the others make covalent linking, not ionic (generally means electrovalent in some texts)


You mean the intermolecular one, that too in an aqueous solution

Yes, you're right! Ionic linkings are stronger! The best example is our kitchen salt, which your trying to separate stove, you can't because the boiling point of the NaCl is 900 °C and only in industries is possible to separate the sodium from the chlorine.

How does the electronegativity of the halogens & hence the H-X bond polarity change down the group?

Yes, I made a mistake.

Does not constitute an explanation, nor fits the data very well!

Yes, I don't know how to do this question.

Also, the statement

makes it a bit ambiguous to know whether you've understood the concept of hydrogen bonding

I didn't even internalized this subject. Could you recommend me a video lesson about this subject?

 

[baldbrain]

Could you recommend me a video lesson about this subject?

To begin with, watch this:

 

[baldbrain]

@José Ricardo After watching that, you can guess that these molecules get 'associated' (get closer together due to attractions) with each other. Think, how will that affect the boiling point?

 

[Fewmet]

I find that working out answers to questions like these are best done by starting with a particle level description (i.e., what the atoms or molecules are doing). An excellent written source for that is Richard Feynman's Atoms in Motion.

There are video's of Feynman informally talking about much of the material, like this and this. I find the text, though, more useful.