# How do we decide whether salts are weak acids or weak bases?

Apr 8, 2017

By the $p H$ of the aqueous solution prepared from the salt..........

#### Explanation:

Weak acids typically give salts that give slightly alkaline solutions.

And weak bases, give salts that give slightly acidic solutions.

$\text{Sodium carbonate}$ is derived from carbonic acid, a WEAK acid, and in solution, this would give a basic solution due to the following equilbrium:

$N {a}_{2} C {O}_{3} \left(s\right) + {H}_{2} O r i g h t \le f t h a r p \infty n s N {a}^{+} {\text{^(-)HCO_3 + }}^{-} O H$

And this would give rise to a solution whose $p H > 7$. How much more I don't know without quoting details.

Other salts of weak acids include ${\text{Na"_2"HPO}}_{4}$, $\text{NaF}$, and ${\text{NaO"_2"CCH}}_{3}$: all of these salts would give solutions that were alkaline..........