Sapling #13

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Anna Martin 2l
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Sapling #13

Postby Anna Martin 2l » Sat Nov 14, 2020 7:33 pm

For the question #13 of the Sapling homework, how would you determine how many water molecules that the Urea molecule can hydrogen bond with?

Katie Lam 2J
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Re: Sapling #13

Postby Katie Lam 2J » Sat Nov 14, 2020 7:39 pm

Hey Anna! Hydrogen bonds occur between an H atom and either an N, O, or F atom. Therefore, the oxygen can bond with 2 H2O molecules. The 4 hydrogens each bond with one H20 molecule. Each nitrogen can also bond with one molecule. If you add up all of those bonds, you get 8 bonds total. Hope this helps!

Sabrina Galvan 3J
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Re: Sapling #13

Postby Sabrina Galvan 3J » Sat Nov 14, 2020 7:46 pm

For an hydrogen bond to form, a hydrogen atom has to be bonded to a strongly electronegative atom of one molecule, and another strongly electronegative atom of another molecule.
N-H bonds are polar, as nitrogen is an electronegative atom. So the H in that bond is slightly positive and will create a hydrogen bond with the O in a water molecule, so for every N-H bond, there is a hydrogen bond for the H. Additionally, N has a lone pair of electrons, so it can form another hydrogen bond. This is similar to O, which is also an electronegative atom, and it has two lone electron pairs, so it can for two hydrogen bonds for each oxygen atom. The carbon cannot form a hydrogen bond because it is not electronegative enough. Following these guidelines, Urea can form hydrogen bonds with 8 water molecules.

Vince Li 2A
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Re: Sapling #13

Postby Vince Li 2A » Sat Nov 14, 2020 7:57 pm

Yeah, it took me a while to figure this out, but here is what I learned: A hydrogen bond can bond with a highly electronegative atom at the lone pair location, and it can also bond to the slight positive hydrogen atoms. Based on looking at the molecule, you can see that there can be a hydrogen bond at all four hydrogen locations. Now, you know that hydrogen bonds can form with highly electronegative atoms, such as N and O. And because I mentioned before that they form bonds at the lone pair locations, the N atoms and O atom added up have four lone pair locations. As a result, those are the last four bond locations. Four plus four is eight water molecules, which is the answer.

Ethan Goode 2H
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Re: Sapling #13

Postby Ethan Goode 2H » Sat Nov 14, 2020 7:58 pm

You want to look at the partial charges for the hydrogens, oxygens, and nitrogen. The partially positive hydrogens are able to bond to one water molecule each, same with the partially negative nitrogen. The partially negative oxygen is able to bond to 2 hydrogens on the water, giving 8.

Carolina Gomez 2G
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Re: Sapling #13

Postby Carolina Gomez 2G » Sun Nov 15, 2020 5:51 pm

Hydrogen bonds form between Hydrogen atoms that are bonded with highly electronegative atoms and a highly electronegative atom with a lone pair (Nitrogen, Oxygen, or Fluorine). In example 13, there are 4 Hydrogen atoms that are bonded to Nitrogen atoms (highly electronegative atom) which causes a partial positive charge on the H atom, therefore H-bonds can from on each H atom. There are also 2 Nitrogen atoms with a lone pair, which can form an H-bond with partially positive H atoms since the N atoms have a lone pair. The Oxygen can also form 2 H-bonds because it has 2 lone pairs. There are a total of 8 H-bonds possible: 4 from the Hydrogen atoms, 2 from the Nitrogen atoms, and 2 from the Oxygen atom.

Jaclyn Schwartz 1I
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Re: Sapling #13

Postby Jaclyn Schwartz 1I » Sun Nov 15, 2020 8:08 pm

Ya it took me awhile to figure it out as well. But look at the electronegative atoms with lone pairs and the hydrogen atoms. The 4 hydrogens are able to form 4 hydrogen bonds with electronegative atoms. There are 2 nitrogen with a lone pair each so they can form a hydrogen bond each so that is 2 more bonds. And the oxygen has 2 lobe pairs so it can form 2 hydrogen bonds, which makes a total of 8.

Dominic Benna 2E
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Re: Sapling #13

Postby Dominic Benna 2E » Sun Nov 15, 2020 8:48 pm

See how many electron pairs connected to either a N,O, or F atom and each one can pair with one water molecule.

Morgan Gee 3B
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Re: Sapling #13

Postby Morgan Gee 3B » Sun Nov 15, 2020 8:53 pm

Water (H2O) has a partial positive charge on hydrogen and partial negative charge on oxygen. This means that we need to look for atoms that have a partial positive or partial negative. This can be determined through comparing the electronegativity of the different bonded atoms in urea. For example, a C=O bond has a partial negative on oxygen and partial positive on carbon. This is because oxygen is more electronegative than carbon, so it desires electrons to a greater degree. The partial positive hydrogen from water can then bond to the partial negative of the oxygen in the C=O bond.


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