## determining number of hydrogen bonding sites

TYun_1C
Posts: 52
Joined: Wed Sep 11, 2019 12:16 am

### determining number of hydrogen bonding sites

How do you determine the number of hydrogen bonding sites? Like the last question on test 2 or 41.d of the marshmallow practice test?

Sebastian Lee 1L
Posts: 157
Joined: Fri Aug 09, 2019 12:15 am
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### Re: determining number of hydrogen bonding sites

Recall that hydrogen bonds can form when a hydrogen that is bonded to a Nitrogen, Oxygen, or Fluorine is strongly attracted to a Nitrogen, Oxygen, or Fluorine with a lone pair. In problems where it asks you to find how many hydrogen bonding sites there are, you should look for the hydrogens bonded to N, O, or F as well as N, O, or F with lone pairs. The hydrogens have strong positive partial charges that will attract them to other molecules that can hydrogen bond. Meanwhile, the N, O, or F has a strong negative partial charge and a lone pair that can make a hydrogen bond with a hydrogen from a different molecule. So if the question asks for how many hydrogen bonds a molecule can make, make sure to count all hydrogens that are bonded to N, O, or F and all the lone pairs on N, O, or F. Note that Oxygen may be able to make 2 hydrogen bonds if it has 2 lone pairs so be sure to count both. However, if the question asks how many ATOMS can make hydrogen bonds, only count each atom once (not like the lone pairs).

Kendra Barreras 3E
Posts: 51
Joined: Mon Sep 23, 2019 12:16 am

### Re: determining number of hydrogen bonding sites

Sebastian Lee 1H wrote:Recall that hydrogen bonds can form when a hydrogen that is bonded to a Nitrogen, Oxygen, or Fluorine is strongly attracted to a Nitrogen, Oxygen, or Fluorine with a lone pair. In problems where it asks you to find how many hydrogen bonding sites there are, you should look for the hydrogens bonded to N, O, or F as well as N, O, or F with lone pairs. The hydrogens have strong positive partial charges that will attract them to other molecules that can hydrogen bond. Meanwhile, the N, O, or F has a strong negative partial charge and a lone pair that can make a hydrogen bond with a hydrogen from a different molecule. So if the question asks for how many hydrogen bonds a molecule can make, make sure to count all hydrogens that are bonded to N, O, or F and all the lone pairs on N, O, or F. Note that Oxygen may be able to make 2 hydrogen bonds if it has 2 lone pairs so be sure to count both. However, if the question asks how many ATOMS can make hydrogen bonds, only count each atom once (not like the lone pairs).

This was really helpful, I was honestly confused because I remember the UA mentioned something about that in the review session but I was confused by it.

TYun_1C
Posts: 52
Joined: Wed Sep 11, 2019 12:16 am

### Re: determining number of hydrogen bonding sites

Sebastian Lee 1H wrote:Recall that hydrogen bonds can form when a hydrogen that is bonded to a Nitrogen, Oxygen, or Fluorine is strongly attracted to a Nitrogen, Oxygen, or Fluorine with a lone pair. In problems where it asks you to find how many hydrogen bonding sites there are, you should look for the hydrogens bonded to N, O, or F as well as N, O, or F with lone pairs. The hydrogens have strong positive partial charges that will attract them to other molecules that can hydrogen bond. Meanwhile, the N, O, or F has a strong negative partial charge and a lone pair that can make a hydrogen bond with a hydrogen from a different molecule. So if the question asks for how many hydrogen bonds a molecule can make, make sure to count all hydrogens that are bonded to N, O, or F and all the lone pairs on N, O, or F. Note that Oxygen may be able to make 2 hydrogen bonds if it has 2 lone pairs so be sure to count both. However, if the question asks how many ATOMS can make hydrogen bonds, only count each atom once (not like the lone pairs).

This helped me a lot, thank you so much!!!

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