Electrolyte Types

Let's start with a definition

a species that, when put in water, separates into cations and anions

AB(aq) → A+(aq) + B(aq)

This is called an ionization when AB is a covalent compound.
It is called a dissociation when AB is an ionic compound.

Percent Ionization: We can communicate the degree to which the electrolyte ionizes by showing the amount ionized (the A+ or the B) as a percentage of the original concentration of the parent species (the AB species)

%ionized =    [A+]  [AB]original × 100%

The "3" Types of Electrolytes

Even though we have electrolytes that span the entire range of percent ionization, we really only refer to them as being one of three types:

  • strong: completely ionized, a full 100%
  • non: not ionized at all, 0%, it is NOT an electrolyte
  • weak: ionized more than 0%, but less than 100%

Hey, I do realize that this really means there are only TWO types of electrolytes: strong and weak. The "third" type is a non-electrolyte which means it is not an electrolyte. Weird I know. But sometimes we name things based on what they aren't. It is often important to explicitly point out that this is NOT an electrolyte, thus we label it as a non-electrolyte. Sugar (sucrose) is a good example of a very soluble compound in water, but it does not ionize at all - a non-electrolyte.

As for the strange usage of "weak" for everything that isn't 100% (strong)... that is just a traditional way of thinking. The good news is that almost all weak electrolytes are on the very low end of percent ionization. Like at and below 1% actually. Then, a few get up over 1% and float towards 10%. And very very few make it up over 10%. So the term "weak" is a pretty good term for the majority of all this electrolytes.

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