Question #b984a

Jul 31, 2017

They would be acids.

Explanation:

Most substances that dissociate into constituent ions in aqueous solution are ionic compounds ($\text{KCl}$, $\text{NaBr}$, ${\text{AlCl}}_{3}$, etc.). These solvated ions carry a current between electrodes and conduct electricity.

However, there some very important covalent compounds that dissociate as well, and they are called acids.

Acids have a few different definitions, but they can be categorized into two main groups: strong acids and weak acids.

Strong acids are those that dissociate essentially completely in solution; i.e. there isn't really an equilibrium established between between the composite ions and the molecule itself. There are seven common strong acids:

• $\text{HCl}$

• ${\text{HNO}}_{3}$

• $\text{HBr}$

• $\text{HI}$

• ${\text{HClO}}_{3}$

• ${\text{HClO}}_{4}$

• ${\text{H"_2"SO}}_{4}$

(notice there is only one diprotic acid: sulfuric acid)

Weak acids essentially consist of all acids that are not the above seven. They do not dissociate to near completion, and have a measurable equilibrium between molecule and dissociated ions.

Weak acids have an acid dissociation constant, denoted ${K}_{a}$, that describes the ratio of concentration of component ions to concentration of the whole molecule, and the value will always be less than $1$ (with the exception of the hydronium ion (${\text{H"_3"O}}^{+}$), whose value is $1$).

For example, for the weak acid $\text{HF}$, we have the equilibrium expression

${K}_{a} = \left(\left[\text{H"^+]["F"^-])/(["HF}\right]\right)$

The ${K}_{a}$ value for hydrofluoric acid is $7.2 \times {10}^{-} 4$, which indicates the concentration of $\text{HF}$ is greater than that of ${\text{H}}^{+}$ and ${\text{F}}^{-}$; i.e. the equilibrium lies to the left.