What’s the difference between strong and weak acids?
A strong acid ionizes completely in water, while a weak acid partly ionizes. For instance, hydrochloric acid (HCl) and hydrofluoric acid (HF) ionize in water to produce H+( these reactive H+ ions share a lone pair of electrons on the oxygen atom of water (H2O) to form the hydronium ion, H3O+. Therefore, we are more correct if we say that HCl and HF ionize in water to produce H3O+).
If you test the conductivity of the same concentration of HCl and HF, you will notice that the light bulb of the conductivity tester glows brighter with the HCl solution than it glows with the HF solution. This difference in brightness is because of how well each chemical dissociates in water.
For instance, HCl normally dissociates 100% in water. Therefore, HCl is a strong acid and a strong electrolyte. Here is a model showing the dissociation at the symbolic and molecular level.
On the other hand, only a small fraction of HF molecules ionize in water. Here is a model showing the ionization at the symbolic and molecular level.
As you can see, we have a longer arrow pointing towards the reactants and a shorter arrow pointing towards the products. The longer arrow means that the reverse reaction is preferred, and that the products easily combine to get back the reactants. On the other hand, the shorter arrow means that the forward reaction is not preferred, and that only a small fraction of HF ionizes in water. Therefore, HF is a weak acid and a weak electrolyte.
Finally, a strong electrolyte that’s an acid or a base is also a strong acid or a strong base. A weak electrolyte that’s an acid or a base is also a weak acid or a weak base.
To learn more about the general properties of acids, click here.
To learn more about strong and weak electrolytes, click here.