[Thavirg]

I have a test tomorrow about solutions/ dilutions, solubility, and molarity. Can someone help me review or tell me what to study. Can someone explain what polar and no polar means, an what it has to do with water.& what do molecule shapes have to do with this. Another thing is can some one do this example molarity problem for me. How would you prepare 500 mL of .50 M CaCO3 from a stock solution of 1.5 M CaCO3

[CKabes]

So, as far as polarization goes, basically, electrons tend to gather around certain parts of a molecule, and cause that side of a molecule to become charged. If we think about water, we have the Oxygen Molecule, and two close hydrogen molecules. The electrons orbiting the molecule are going to tend to stay away from the close hydrogen protons because they have a positive charge. This means, because the H protons push them away, they 'collect' on the back side of the Oxygen atom and cause that side to be negative. Because all these electrons are hanging out on the back side of oxygen, creating a negative charge, there's nothing to negate the hydrogen protons, so the close hydrogen atoms have a positive charge. Lost yet?

Now that we know water has a + side and a - side, it can work as a magnet. It has two 'poles', making it POLAR!

So, the negative end of water (on the oxygen) can be attracted to a positive H proton on another water molecule, resulting in something called a DIPOLE-DIPOLE bond. Basically, one DIPOLE (water ~ a molecule with two poles) attracts another DIPOLE and forms bonds between molecules.

Here's a link to illustrate: http://www.cfwep.org/education/smsp/images/module04/water_polarity04.jpg

[CKabes]

And as far as dilution goes, just remember this helpful formula, I believe this should be correct:

C_iV_i = C_fV_f

Concentration Initial x Volume Initial = Concentration Final x Volume Final

Solve for your missing variable.
For your case you could say, 1.5y = .50(500) , where y is the ammount you need to add to water. Y=166.6 so i think you could add that to 333.4 ml of water?

I'm not 100% sure, but It sounds pretty good...

[Borek]

If we think about water, we have the Oxygen Molecule, and two close hydrogen molecules.

Atoms. You don't have molecules inside a molecule.

The electrons orbiting the molecule are going to tend to stay away from the close hydrogen protons because they have a positive charge. This means, because the H protons push them away

Since when positive charge repels negative charge?

Because all these electrons are hanging out on the back side of oxygen, creating a negative charge, there's nothing to negate the hydrogen protons, so the close hydrogen atoms have a positive charge. Lost yet?

This part is more or less correct, but not because protons repel electrons, but because oxygen attracts them stronger than hydrogens do.

Now that we know water has a + side and a - side, it can work as a magnet.

No, it is not a magnet. It is an electric dipole. Separated charges don't create a magnetic field.

It has two 'poles', making it POLAR!

So, the negative end of water (on the oxygen) can be attracted to a positive H proton on another water molecule, resulting in something called a DIPOLE-DIPOLE bond. Basically, one DIPOLE (water ~ a molecule with two poles) attracts another DIPOLE and forms bonds between molecules.

More or less OK.