Does Chlorine hydrogen bond

[Oh_Gee]

From GS-6

"Which of the following molecules forms the weakest hydrogen bonds?

a HF
b HCl
c H2O
d H2S










Among the answer choices, S is the least electronegative of the different atoms bonded to hydrogen. This can be deduced from the periodic table: it is below oxygen in Group VI, in a lower period than fluorine, and before chlorine in its period, each of which makes it less electronegative than the other atoms. The relatively low electronegativity translates in a lower force of attraction between the δ- sulfur and neighboring δ+ hydrogens (see H-bonding, CHM 4.2, #3)."


I know F O N hydrogen bond, and according to a lot of GS questions, so does sulfur but what about Chlorine? that was my answer. HCl is a strong acid and would dissociate so wouldn't that make the weakest H bonds if any?

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[AmishExpressWay]

Null

 

[Oh_Gee]

HCl makes very strong inter-molecular (or rather, inter-ion-ular?) bonds because it dissolves into H+ and Cl- ions, the most polar ions possible due to their small ion sizes and high charges, and the fact that the two ions do not bond covalently. However, this is definitely ionic bonding and not hydrogen bonding. But, since HCl is usually considered to dissolve in water, it will form extremely strong hydrogen bonds with water. EXTREMELY STRONG. However, since the question does not state that HCl (aq) is one of the options, this question officially sucks.

Regardless, this is still a bull**** question due to its ambiguity.

so all strong acids can h bond?

 

[AmishExpressWay]

Null

 

[Oh_Gee]

No, strong acids on their own should not be able to hydrogen bond because they are solids. They can only H-bond, and do so really well, in an aqueous solution.

what do you mean they're solid?

 

[AmishExpressWay]

what do you mean they're solid?

That was a mistake sorry lol. HCl is a liquid at STP and DOES form hydrogen bonds. However these hydrogen bonds are weaker than waters, ammonias, or hydroflouric acids due to the large atomic radius of chloride. Large atoms are much less polar because the charge is spread over a larger atomic volume.

H2S ALSO forms hydrogen bonds, but since sulfur is such a large molecule, the hydrogen bonds it forms are very, very weak.

Most textbooks state that only O, N, and F form hydrogen bonds, but that is wrong. O, N, and F simply form the STRONGEST hydrogen bonds, especially when compared to something with weak hydrogen bonds like H2S.

While this is something interesting to understand, I don't think the MCAT would ever ask the test taker to assume that anything other than N, O, or F produce hydrogen bonds.

I apologize if I caused any confusion earlier, it was just hard to understand what the author of that GS exam was trying to ask.

 

[Oh_Gee]

That was a mistake sorry lol. HCl is a liquid at STP and DOES form hydrogen bonds. However these hydrogen bonds are weaker than waters, ammonias, or hydroflouric acids due to the large atomic radius of chloride. Large atoms are much less polar because the charge is spread over a larger atomic volume.

H2S ALSO forms hydrogen bonds, but since sulfur is such a large molecule, the hydrogen bonds it forms are very, very weak.

Most textbooks states that only O, N, and F form hydrogen bonds, but that is wrong. O, N, and F simply form the STRONGEST hydrogen bonds, especially when compared to something with weak hydrogen bonds like H2S.

I apologize if I caused any confusion earlier, it was just hard to understand what the author of that GS exam was trying to ask.

yeah some GS questions make me feel like I'm wasting my time when I click on their forums and see all the arguments about specific questions. so how would you compare H bond strength of Cl and S?

 

[AmishExpressWay]

yeah some GS questions make me feel like I'm wasting my time when I click on their forums and see all the arguments about specific questions. so how would you compare H bond strength of Cl and S?

I'd assume HCl makes stronger hydrogen bonds than H2S for one reason:
1) Chlorine has a higher electronegativity than sulfur. This makes the charge across H and Cl in HCl more spread apart, and is therefore more polar than H2S.

BUT, since H2S has two hydrogens bonded to S, two times the amount of hydrogen bonds are produced for the molecule (just like water!). However, this also means that the charge disparity along either H-S bond is smaller. In all honesty, this is the type of thing that would be better confirmed by experimentation than by speculation.

 

[ayocaptain628]

i think i wouldve done this problem wrt: bond dissociation energy
f and cl are more electronegative b/c they're more rightward so they're out
b/w oxygen and sulfur, sulfur has a larger atomic size .:. lower bond dissociation energy .:. weaker bond strength

 

[MedHopeful20134]

Keep it simple:
Just know that N, O and F can H-bond. Anything else would be weaker. Now between H2S and HCl, Cl is more electronegative, hence H2S should have the weakest H-bonds.

 

[Teleologist]

HCl is a strong acid and would dissociate so wouldn't that make the weakest H bonds if any?

Dissociation doesn't have much if anything to do with hydrogen bonding strength. Consider HF, which actually becomes a stronger acid as concentration goes up, because of stabilizing hydrogen-bonding interactions.