Question

A buffer is made by dissolving `"NaClO"` and `"HClO"` in water. How do you write equations to show how this buffer neutralizes added H+ and OH-?

Answer 1

Consider the buffer system's equilibrium,

`HClO rightleftharpoons ClO^(-) + H^(+)`

where,

`K_"a" = ([ClO^-][H^+])/([HClO]) approx 3.0*10^-8`

Moreover, consider the ionization of water,

`H_2O rightleftharpoons H^(+) + OH^(-)`

where

`K_"w" = [OH^-][H^+] approx 1.0*10^-14`

The preceding equations can be used to understand what happens when protons or hydroxide ions are added to the buffer solution.

This isn't trivial to understand! It may take awhile to comprehend what I'm telling you below.

If we add hydroxide ions, `Q_"w" > K_"w"` transiently.

`HClO` dissociates to restore `K_"w"`. However, in so doing, `Q_"a" < K_"w"`, so `HClO` must dissociate further to restore its equilibrium.

Hence, the `"pH"` will decrease ever so slightly.