Question

Why are diluted weak acids strong electrolytes?

Answer 1

Do you mean why are they not?
Do you mean their conjugates?

Answer 2

I means why they are. Concentrated weak acid is not a conductor, but dilute solutions are.

Answer 3

That's contrary to what we would expect. The more something ionizes, the more ions there are and the higher conductivity.

Answer 4

Are you sure about this?

I'm reading the explanation on chemwiki~ucdavis

let me see if I can make sense of this;

"These weak electrolytes, like the intermediate ones, will be totally dissociated at the limit of zero concentration; But at such a high dilution, the conductivity would be so minute that it would be masked by that of water itself (that is, by the H+ and OH– ions in equilibrium with the massive 55.6 M L–1 concentration of water) — making values of Λ in this region virtually unmeasurable."

So if you have a weak electrolyte, something that only partially dissociates, with a low Ka value, you're going to get a small amount of ions.

Say if we have a minute concentration of weak acid in a solution of water. From the explanation, because there is so much water in comparison to the weak acid, conductivity is generally unmeasurable.

Answer 5

The explanation that a peer gave me was that the weak acid is partially dissociating and reacts with the water, in the dilution, to make acetate, H+, and OH- ions that make the solution more conductive. I think more water(dilution) drives the forward reaction of dissociation, but am not sure.

Dilute weak acid solutions definitely conduct electricity, though. I used a lightbulb setup to check the conductivity of a 0.0001M acetic acid solution and there was a fairly strong light.

Answer 6

Also, UC Davis says that the conductivity of the weak acid cannot be measured, not the solution. I want to say that the 0.0001M acetic acid solution is a strong electrolyte, but UC Davis is saying that the water is the strong electrolyte, not the weak acid with low molarity.

Answer 7

No. Water will not drive fourth dissociation of a weak acid. The Ka tells you how much it will dissociate. Acetic acid, no matter the concentration, is always a weak acid simply because it has a Ka (of 1.8 x 10 ^-5).

Answer 8

So, diluted weak acids are not strong electrolytes. Strong electrolyte = strong acid = has no dissociation constant.