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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: INeedSerotonin on October 19, 2019, 01:16:54 PM

Title: Why is hydrogen's boiling point 20 K?
Post by: INeedSerotonin on October 19, 2019, 01:16:54 PM
Hello

I found this exercise that gave me four explanations to "why is the boiling point of hydrogen so low, i.e., equal to 20 K?", and I had to tell which were true and which were false

Explanations:

I) there are hydrogen bonds;
II) the Van Der Waals forces are weak in intensity;
III) the molecule is non-polar, and there are few electrons;
IV) it is easy to break the covalent bond H-H

Only (II) and (III) are true, but I wonder why (IV) is not. Could you guys please explain it to me? I also am not sure as to why (III) mentions electrons.
Title: Re: Why is hydrogen's boiling point 20 K?
Post by: Corribus on October 19, 2019, 01:53:07 PM
Does boiling have anything to do with breaking covalent bonds?
Title: Re: Why is hydrogen's boiling point 20 K?
Post by: INeedSerotonin on October 19, 2019, 02:34:14 PM
Does boiling have anything to do with breaking covalent bonds?

I remember learning that we need to overcome some kind of force in order to boil something,

So I guess that boiling doesn't have anything to do with breaking covalent bonds, but it is all about breaking intermolecular forces?  ???
Title: Re: Why is hydrogen's boiling point 20 K?
Post by: Corribus on October 19, 2019, 03:02:03 PM
Yes. A phase change doesn't involve breaking covalent bonds,  only intermolecular interactions.  If covalent bonds are broken, it's a chemical reaction. If you need to explain something about a boiling point,  you have to think about factors that influence the strength of intermolecular forces.
Title: Re: Why is hydrogen's boiling point 20 K?
Post by: INeedSerotonin on October 19, 2019, 06:09:51 PM
Yes. A phase change doesn't involve breaking covalent bonds,  only intermolecular interactions.  If covalent bonds are broken, it's a chemical reaction. If you need to explain something about a boiling point,  you have to think about factors that influence the strength of intermolecular forces.

Thank you! ;)
Title: Re: Why is hydrogen's boiling point 20 K?
Post by: Enthalpy on October 21, 2019, 01:52:45 PM
And H-H bonds are strong. As strong as H-Cl for instance.