how can H2O form 4x H-bonds but HF only 2?

[Mcat35]

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http://en.wikipedia.org/wiki/File:3D_model_hydrogen_bonds_in_water.svg

since (hydrogen bonding H must convalently bond to O/N/F) How can water form so many H- bonds, but HF can only form 2? I understand that each lone pair that the oxygen molecule has can form another hydrogen bond. and each hydrogen can form a H-bond to an oxygen, so it makes sense that H2O can form 4x hydrogen bonds.

HOwever it says that HF can only form 2x hydrogen bonds, but the Flourine has 3 lone pairs. Shouldn't it be able to form an H bond with each single lone pair? + another H bond with the Hydrogen to another electronegative element?

For example if we mix HF and H2O what would happen?

 

[ModusProbandi]

http://en.wikipedia.org/wiki/File:3D_model_hydrogen_bonds_in_water.svg

since (hydrogen bonding H must convalently bond to O/N/F) How can water form so many H- bonds, but HF can only form 2? I understand that each lone pair that the oxygen molecule has can form another hydrogen bond. and each hydrogen can form a H-bond to an oxygen, so it makes sense that H2O can form 4x hydrogen bonds.

HOwever it says that HF can only form 2x hydrogen bonds, but the Flourine has 3 lone pairs. Shouldn't it be able to form an H bond with each single lone pair? + another H bond with the Hydrogen to another electronegative element?

For example if we mix HF and H2O what would happen?

Sure, you got 3 H-bond acceptors on F. But guess what, you've only got one H-bond donor per molecule.

 

[golgiapparatus88]

http://en.wikipedia.org/wiki/File:3D_model_hydrogen_bonds_in_water.svg

since (hydrogen bonding H must convalently bond to O/N/F) How can water form so many H- bonds, but HF can only form 2? I understand that each lone pair that the oxygen molecule has can form another hydrogen bond. and each hydrogen can form a H-bond to an oxygen, so it makes sense that H2O can form 4x hydrogen bonds.

HOwever it says that HF can only form 2x hydrogen bonds, but the Flourine has 3 lone pairs. Shouldn't it be able to form an H bond with each single lone pair? + another H bond with the Hydrogen to another electronegative element?

For example if we mix HF and H2O what would happen?

Hi again,

"Not all molecules with potential lone electrons can make hydrogen bonds. HF makes a linear zig-zag structure with 2 hydrogen bonds. This has to do with the density, molecular weight, and size of the molecule."

I found that online with some searching. I'd just remember the fact that H20 is the best at H-bond compared to other covalent molecules and H-F forms a linear zig-zag structure with H-bonds.

 

[Mcat35]

Hi again,

"Not all molecules with potential lone electrons can make hydrogen bonds. HF makes a linear zig-zag structure with 2 hydrogen bonds. This has to do with the density, molecular weight, and size of the molecule."

I found that online with some searching. I'd just remember the fact that H20 is the best at H-bond compared to other covalent molecules and H-F forms a linear zig-zag structure with H-bonds.

ok thanks again, I was afraid that they will bust out some question to ask you how many H bonds something other than H2O can make. Like HF I would never know lol...

 

[Mcat35]

Sure, you got 3 H-bond acceptors on F. But guess what, you've only got one H-bond donor per molecule.

ya but what if you mix HF with H2O? Or is H bond only concerned with the same molecules?

 

[golgiapparatus88]

ok thanks again, I was afraid that they will bust out some question to ask you how many H bonds something other than H2O can make. Like HF I would never know lol...

Luckily, you can only have H-bonding with molecules that have N,O,F bonded to a hydrogen as well as a lone pair. As long as you know that you'll be ok. Remember that compounds without a hydrogen attached to those 3 elements will not hydrogen bond. For example, an diethyl ether CH3CH2-O-CH2CH3 will not H-bond.

Here's a cool picture that sums up a lot of this stuff.
http://en.wikipedia.org/wiki/File:WikipediaHDonorAcceptor.png

Also, just as a fun tidbit. H-bonding is not all equal. As covalent bond strength increases, the weaker the H-bond and vise versa.

::Thank you Berkeley Review for overloading me with information::

 

[golgiapparatus88]

ya but what if you mix HF with H2O? Or is H bond only concerned with the same molecules?

You'd definitely get hydrogen bonding between the two. As long as it has a lone pair, is N/O/F, or has an acidic hydrogen attached to either of those 3, you can get H-bonding.

Please don't take offense to this (because it's good to ask questions) but I'd go back and read some of these chapters again. The questions you are asking are relatively simple that any MCAT book will cover. Most people on SDN including myself don't mind answering these types of questions, but for your sake, you'll get a lot more out of studying a book than bits and pieces of info on a forum.

 

[Mcat35]

You'd definitely get hydrogen bonding between the two. As long as it has a lone pair, is N/O/F, or has an acidic hydrogen attached to either of those 3, you can get H-bonding.

Please don't take offense to this (because it's good to ask questions) but I'd go back and read some of these chapters again. The questions you are asking are relatively simple that any MCAT book will cover. Most people on SDN including myself don't mind answering these types of questions, but for your sake, you'll get a lot more out of studying a book than bits and pieces of info on a forum.

no problem, and I'm not. I actually have reviewed plenty and now just doing practice problems which triggered some of my thinking.

thanks for all your help!

 

[golgiapparatus88]

no problem, and I'm not. I actually have reviewed plenty and now just doing practice problems which triggered some of my thinking.

thanks for all your help!

No problem. Just looking out for you 😎