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Hydrogen Bonding Question

Posted: Sun Nov 11, 2018 4:04 pm
by Michelle Fu 1H
Why is the hydrogen bond so much stronger than other Van Der Waals forces? Also why is the energy -20 kJ per mole as opposed to just 20 kJ?

Re: Hydrogen Bonding Question

Posted: Sun Nov 11, 2018 4:11 pm
by 305113590
Van der Waals are transient intermolecular forces, meaning that the interactions between molecules are temporary and do not last long. Van der Waals are found everywhere. Hydrogen bonds are a stronger intermolecular force because of the difference between electronegativities. For example, water has a slightly negative oxygen and slightly positive hydrogens. These slightly positive and negative charges are attributed to the difference in electronegativity.

Re: Hydrogen Bonding Question

Posted: Sun Nov 11, 2018 4:18 pm
by Soumya Ravichandran 4H
With regards to why the energy is negative, I think it is because it takes a huge amount of energy to break the hydrogen bonds due to the difference in electronegativities. Since Fluorine is the most electronegative atom, the closer you bond hydrogen with an element next to fluorine, the higher the energy and strength of the bond. This is the case in water as well.

Re: Hydrogen Bonding Question

Posted: Tue Nov 13, 2018 1:19 pm
by MaggieMatern_Dis1H
Hydrogen bonds are less transient than other VDW, making them stronger. A fluctuating dipole is instantaneous and unpredictable, whereas the partial negative/positive charges found in hydrogen bonds are more constant, and can be thought of as being 'always present'.

It is easier to break a temporary bond than a constant one.