Hard chemistry question- please help!?

Question

OK so for my lab I was collecting data for the properties of solutions in electrolytes and nonelectrolytes.
My group A solutions included CaCl^2, AlCl^3, and NaCl? Each had 0.05 M
Then I collected the conductivity for each using a probe and I got:
CaCl^2- 8210 conductivity
AlCl^3- 4993 conductivity
NaCl- 6502 conductivity

Now, why is it that the group A compounds, each having the same concentration (0.05 M) have such large differences as far as conductivity values? How could I write an equation of dissociation for each?

Please help!

Answer 1

The conductivity depends on how many free electrons are available to travel down the potential gradient.

Each of the salts form +ve and -ve ions in solution. And the number of ions depends on the atomic number of the mettalic or non metallic parts of the compound. If you look in the periodic table, you will see the differences in the atomic numbers of Ca, Al, and Na. and number of electrons in the outer orbitals dictates how much charge will be present on the ions. For example, Na+ has one electron difficient, while Ca2+ has 2 electron difficiency and Al3+ has 3 electron difficiency. This means these positive ions have 1,2 or 3 positive charges on them or their negative counterparts have 1,2 or 3 negative charges on them. Also, the electronegativity of Na is 0.9, that of Ca is 1.0 and that of Al is 1.5. Electronegativity tells us how tightly these atoms want to hold on to the electrons, thus reflecting on how difficult it is for them to ionise. So, even though you have same number of molecules in each solution, the charges of the ions are different. The more the charge on the ion the more the conductivity provided they all have equal electronegativity. In this case even though Al3+ has more charge on it, it's high electronegativity prevents it from ionising as easily as Ca or Na. That's why you have highest conductivity for CaCl2 than AlCl3.

Answer 2

Depends on the strength of bonding.