How does Ka change with concentration?

Dec 9, 2014

Ka stays constant regardless of concentration

Ka is the acid dissociation constant
Remember that in equilibrium, we take the concentration of the products (raised to the power of their coefficient, and multiplied together) divided by the concentration of the reactants (treated likewise)

for a generic acid A, it measures the breakdown of an acid (H-A) into the conjugate base (A-) and hydrogen ion (H+):

$H A \leftrightarrow {H}^{+} + {A}^{-}$

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

Depending on the characteristics of the acid (H-A), it will dissolve and release H+ ions at a fixed proportion to its concentration
in other words, the amount of H+ produced is proportional to the amount of H-A we started out with

So, Ka will remain constant for a particular acid despite a change in concentration (all other conditions, such as temperature, held constant)