Question

Is the purpose of a buffer system to keep a solution neutral? If not, what is the purpose?

Answer 1

The purpose of an (aqueous) buffer is to maintain the `pH` of the given solution around a given value.........

Explanation:

The buffer equation, which is derived in the later link is:

`log_10K_a=log_10[H_3O^+] + log_10{[[A^-]]/[[HA]]}`

Upon rearrangement:

`-log_10[H_3O^+] = -log_10K_a+ log_10{[[A^-]]/[[HA]]}`

And upon simplification:

`pH=pK_a+log_10{[[A^-]]/[[HA]]}`.

The `pH` could be neutral, or ACIDIC, or BASIC, depending on `pK_a`, or the proportions of acid or base used.

A buffer then acts to keep the `pH` tolerably close to the `pK_a` of the starting acid. If the buffer is composed of equal concentrations of acid and conjugate base, `pH=pK_a`; why?

Depending on the capacity of the buffer, addition of small quantities of `H_3O^+` or `HO^-` protonate the conjugate base or deprotonate the acid, such that the `pH` remains fairly close to a predetermined value. Biological systems (including our digestion and respiration processes) are extensively buffered.

See [here for the derivation of the formula.](https://socratic.org/questions/how-do-buffers-maintain-ph)