Which solution will have the greatest electrical conductivity?

Question

A. 0.50MHCl
B. 0.10MRbOH
C. 0.50MK3PO4
D. 2.0MC6H12O6

I thought the answer would be B, but it is C. Is it not B because the Ka is too small? Otherwise, C is has the smallest Ka.

Answer 1

The concn as well as if it is a strong/weak acid/electrolyte. D ionizes 0% and doesn't conduct at all. Both HCl and RbOH are strong electrolytes in solution but HCl is stronger; therefore, it will have more ions so A is better than B. The best is K3PO4. That is an ionic solid, it is a strong electrolyte in solution, AND you will notice it breaks up into 4 ions, K3PO4 ==> 3K^+ + PO4^-3; therefore, for the same concn as HCl, you get four ions to conduct whereas with HCl we have only two.

Answer 2

How do you know if D ionizes or not? Is it because it doesn't have a metal or because it is a weak acid?

So the more ions it have, the better the conductivity, eventhough HCl is one of the strongest acids?

Answer 3

Let's say we take 1 L of solution. In 0.5 M HCl we will have 0.5 mol H^+ and -0.5 mol Cl^- or 1 mol of ions to conduct.
With K3PO4, we will have 0.5 x 3 = 1.5 moles K^+ and 0.5 mol PO4^- for 2 moles to conduct which is better than the 1 of HCl. D? Actually, that isn't a very good part of the question. I looked at it and saw glucose, a sugar. They don't ionize at all. However, there ARE some organic compounds that have the formula C6H12O6 that might ionize more. The spirit of the question, though, is for it to be sugar. That's part experience.

Answer 4

I understand now, thanks for your help! :)