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Topic: Why is water polar and how does water dissolve ionic compounds?  (Read 6859 times)

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crazybouttennis

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I know water is polar because the oxygen atom has a stronger pull on the electrons than the hydrogen atoms, so the sharing of electrons is unequal...but how do I explain why water is polar using the KMT?

When an ionic compound is placed in water, the ions are pulled out of their lattice by the water molecules.  The water molecules can pull them away because they have enough kinetic energy to resist the ionic bonds that hold the ions in the lattice.  Is this right?  (I also need to answer this using the KMT.)  My answer doesn't seem right because aren't ionic bonds stronger than the ion-dipole attractions that would occur when an ionic compound is placed in water?  Do water molecules have that much kinetic energy?

hay

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Re:Why is water polar and how does water dissolve ionic compounds?
« Reply #1 on: April 03, 2006, 04:53:08 AM »
Not sure what you mean by KMT, but I could help you explain why water molecule is considered polar. Let's look into the shape of water molecule

H2O, O has 2 lone pairs and 2 bond pairs, by VSPER theory, their molecule shape is bent.  

so the sharing of electrons is unequal.. > Shall clarify this. O atom electronegativity is higher than of H atom, more "bonded electrons" ( or the cloud ) would be closer to O atom therefore making O slightly negative charge. We term in delta negative and H-O bond is polar.

As mention, the shape is bent(asymmetrical), the delta +  of H and delta - of O does not coincide( does not cancel each other ). Hence making H2O a polar molecule. A physicist would be able to explain in details regarding the pull/electrostatic attraction/energy.


because aren't ionic bonds stronger than the ion-dipole attractions that would occur when an ionic compound is placed in water?.

Did some research before, there's a formula to calculate the energy needed and the energy produced. You may want to google it > Ion dipole attraction. It's kind of advanced( maybe for undergraduate/graduate standard ). Nonetheless, the general rule is iondipole attracion > Ionic bond.

From what I have learnt, this has nothing to do with kinetic enery of water molecule. When h2o molecules approach the ionic bond, large amount of energy is produced which is used to overcome the electrostatic attraction of ionic compounds. Hence making the respecitive cations/anions soluble in water. ( Being able to roam freely ).

Correct me if I am wrong, just my 2 cents

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crazybouttennis

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Re:Why is water polar and how does water dissolve ionic compounds?
« Reply #3 on: April 03, 2006, 09:14:56 PM »
thanks!

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