# What's the equilibrium pH of an initially 0.64M solution of the monoprotic acid benzoic acid (HA) at #25^@ "C"# (Ka = 6.3 x 10^-5) ?

##### 1 Answer

See below:

#### Explanation:

Start by setting up an ICE table:

We have the following reaction:

And we have an initial concentration of

Now using the

From our ice table and the values given, we can plug all of the equilibrium values into the

However, the change in concentration of the acid can be considered negligible, due to

The equation above can also be solved by setting up a quadratic equation, but you save time by making the assumption that the change in concentration is negligible - and it rounds off to the same answer.

Hence:

There the equation becomes: