# An acid with a small Ka value would be what type of acid?

Apr 13, 2017

#### Answer:

$\text{A weak acid............}$

#### Explanation:

The strength of an acid is assessed by the completeness of the following acid dissociation reaction:

$H A + {H}_{2} O r i g h t \le f t h a r p \infty n s {H}_{3} {O}^{+} + {A}^{-}$

And we can write an acid dissociation constant, ${K}_{a}$, such that..

${K}_{a} = \frac{\left[{H}_{3} {O}^{+}\right] \left[{A}^{-}\right]}{\left[H A\right]}$

Given this quotient, if ${K}_{a}$ is large (or at least >1), then at equilibrium, $\left[{H}_{3} {O}^{+}\right]$ is large. See this site. For the stronger acids, ${H}_{2} S {O}_{4}$, $H C l {O}_{4}$, $H X \left(X \ne F\right)$, $H N {O}_{3}$, their measured ${K}_{a} \ge 1$.

And for weaker acids, ${K}_{a} < 1$.