# Question #ce2a2

Apr 28, 2017

To understand why this is, we'll need to take a look at how a buffer works.

#### Explanation:

A buffer, by definition, is a solution containing a weak acid, and it's conjugate base (usually added through the form of a salt). This can also be made by a weak base and it's conjugate acid.

The main selling point of a buffer is that it minimizes pH changes within a certain range. How? Consider the balanced chemical equation for the acid-dissociation reaction for HCN:

$H C {N}_{\left(a q\right)} + {H}_{2} {O}_{\left(l\right)} r i g h t \le f t h a r p \infty n s C {N}_{\left(a q\right)}^{-} + {H}_{3} {O}_{\left(a q\right)}^{+}$

The idea is that you have significant concentrations of both your weak acid ($H C N$) and conjugate base ($C {N}^{-}$).

Now, if you add some strong acid (ex. $H C l$) to this buffer solution, it will react with your weak base, and produce conjugate base and water (the reverse of the above reaction). Hence, you will not see a drastic change in pH. Same is true if you add a conjugate base -- it will react with the conjugate acid to produce conjugate base and water.

That, on an intuitive level, is how a buffer works. Your buffer satisfies those conditions, as you have concentrations of both a weak acid and conjugate base.

If you'd like some additional information on buffers, check out this video .

How do you determine in what pH range a buffer works? Learn about that here .

Hope that helps :)