melting points

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Andrew Jang 4D
Posts: 50
Joined: Sat Aug 17, 2019 12:18 am

melting points

Postby Andrew Jang 4D » Mon Nov 11, 2019 2:23 am

why is H2O's melting point 0 degrees C while H2S has a melting point of -86 degrees C?

Andrew Pfeiffer 2E
Posts: 79
Joined: Sat Sep 28, 2019 12:16 am

Re: melting points

Postby Andrew Pfeiffer 2E » Mon Nov 11, 2019 9:37 am

Water molecules undergo intense hydrogen bonding between the oxygen and hydrogen atoms. This makes it significantly harder for the intermolecular forces to be overcome to melt ice. Conversely, H2S has dipole-dipole interactions (S being negative and H positive). While these dipole-dipole interactions are important, they are not nearly as strong as the hydrogen bonding in H2O, and hence, the lower melting point.

IScarvie 1E
Posts: 66
Joined: Sat Aug 17, 2019 12:16 am

Re: melting points

Postby IScarvie 1E » Mon Nov 11, 2019 5:17 pm

Another way to think about it is that O is more electronegative than S, so its dipole moments are more dramatic than H2S's. The positive and negative ends form stronger bonds because of it.

905416023
Posts: 54
Joined: Thu Jul 25, 2019 12:17 am

Re: melting points

Postby 905416023 » Mon Nov 11, 2019 6:28 pm

So hydrogen bonds make the molecule harder to break apart? So then they have a higher boiling point?

Rory Simpson 2F
Posts: 91
Joined: Fri Aug 09, 2019 12:17 am

Re: melting points

Postby Rory Simpson 2F » Mon Nov 11, 2019 7:47 pm

905416023 wrote:So hydrogen bonds make the molecule harder to break apart? So then they have a higher boiling point?


Yes, the strength of hydrogen bonds causes the molecules to have a greater intermolecular attraction which increases their melting and boiling points.

Shail Avasthi 3C
Posts: 81
Joined: Fri Aug 30, 2019 12:17 am

Re: melting points

Postby Shail Avasthi 3C » Mon Nov 11, 2019 10:56 pm

Hydrogen bonds are stronger than dipole/dipole or induced dipole/induced dipole interactions. H2O has the ability to hydrogen bond with itself because of the H-O bond, while H2S cannot. This accounts for H2O's higher melting point.

Shrayes Raman
Posts: 93
Joined: Sat Jul 20, 2019 12:15 am

Re: melting points

Postby Shrayes Raman » Wed Nov 13, 2019 12:08 am

H20 has rather strong hydrogen interactions that H2S does not


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