How does the degree of dissociation affect ka?

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How does the degree of dissociation affect ka?

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Answer 1 · 2014-09-07T04:24:12

The larger the value of $K_{a}$ $K_a$ , the greater the extent of dissociation.

For any acid, $H A$ $HA$ , we can write the dissociation process as

$H A (a q) \leftrightarrow H^{+} (a q) + A^{-} (a q)$ $HA(aq) harr H^+(aq) + A^(-)(aq)$

The equilibrium constant for this process is defined as the ratio of equilibrium products and reactants:

$K_{a} = \frac{[H^{+}] [A^{-}]}{[H A]}$ $K_a={[H^+][A^(-)]}/([HA])$

If $K_{a}$ $K_a$ is large, then the concentration of dissociated ions is larger than the concentration of dissolved acid, $[H A]$ $[HA]$

Examples (assumes the total concentration of acid is 1 M):

If $K_{a} = 0.03$ $K_a=0.03$ then the degree of dissociation is 15.9%, but if
$K_{a} = 0.05$ $K_a=0.05$ then the degree of dissociation is 20.0%, and if
$K_{a} = 3.8$ $K_a=3.8$ then the degree of dissociation is 82.2%

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How does the degree of dissociation affect ka?

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