chemistry

2007-05-05 1:19 am
is there any differences between attractive force between water molecules and common can der waal's force?

回答 (4)

2007-05-05 1:24 am
✔ 最佳答案
Do you mean van der waal's force ?
There's , certainly , NO difference between them!
The attractive force between water molecules is equal to the van der waal's force ,
as the water molecules are held by the van der waal's force !!

But , don't mix up with the covalent bond , which holds the atoms in a molecule !
2007-05-05 2:21 am
is there any differences between attractive force between water molecules and common can der waal's force?
There is of course a difference between forces holding H2O molecules together and van der waals' force. The force holding H2O together is called inter-hydrogen bonding. It is much stronger than the so-called van der waals' force. Why? This is because hydrogen bond is formed between highly electronegative atoms (such as N, O and F with lone pair e- on them) and the small size hydrogen atoms.
How can hydrogen bond be formed? As you know, hydrogen atom is small in size and the outermost shell e- contains only one e-. This implies that the nuclear charge coming from the nucleus,the proton, is thus weakly shielded by the outermost electron. As a result, the hydrogen atom is highly +ve charged. This makes the small hydrogen atom become bare(赤裸). The small size and the high charge density of the hydrogen atom can approach and attract the alone pair e- of the highly electronegative atoms more easily. As a result, the force used to hold water molecule is much stronger than those without hydrogen-bond formation. [charge density = charge of the atom除以volume of the atom] See the following example.
The boiling point (b.p.) of CH3OCH3(a ether) is lower than that of CH3CH2OH. For ether molecules are held by weak van der waals' force (dipole-dipole attraction) comparing CH3CH2OH molecules held by strong inter-hydrogen bondings. The oxygen atom of ether ( Oδ- ) attracts the carbon atom (C δ+) when ether molecules laying up beside one another.
The strength of bonding: covalent bond: hydrogen: van der waals' force is 100: 10: 1
I hope you may find my writing helpful.
2007-05-05 1:50 am
Yes, there is.

Attractive force between water molecules = Hydrogen bonding.

Hydrogen bonding is a type of van der Waal's forces.

Other van der Waal's forces include permanent dipole-permanent dipole (pd-pd) interaction and instantaneous dipole-induced dipole (id-id) interaction.

Pd-pd interaction exists between polar molecules. Id-id interaction exists between BOTH polar and non-polar molecules. Hydrogen bonding ONLY exists between water molecules.

Hope this has helped you. =)
2007-05-05 1:46 am
there is no differences
water molecules have simple molecular structure
and the molecules are held together by weak van der Waals' force
van der Waals' force is also called London force
and for one water molecule
the force between hydrogen atoms and oxygen atom is strong covalent bond
參考: me*


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