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-?

May 6, 2018

Consider the buffer system's equilibrium,

$H C l O r i g h t \le f t h a r p \infty n s C l {O}^{-} + {H}^{+}$

where,

${K}_{\text{a}} = \frac{\left[C l {O}^{-}\right] \left[{H}^{+}\right]}{\left[H C l O\right]} \approx 3.0 \cdot {10}^{-} 8$

Moreover, consider the ionization of water,

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

where

${K}_{\text{w}} = \left[O {H}^{-}\right] \left[{H}^{+}\right] \approx 1.0 \cdot {10}^{-} 14$

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, ${Q}_{\text{w" > K_"w}}$ transiently.

$H C l O$ dissociates to restore ${K}_{\text{w}}$. However, in so doing, ${Q}_{\text{a" < K_"w}}$, so $H C l O$ must dissociate further to restore its equilibrium.

Hence, the $\text{pH}$ will decrease ever so slightly.