# What is an example of a pH practice problem?

Jun 15, 2014

Generally, most pH problems ask you to determine pH from $\left[{H}^{+}\right]$ the hydrogen ion concentration,or conversely, determine the $\left[{H}^{+}\right]$ from the pH.

Let's look at the strong acid HCl, hydrochloride acid, which has a concentration of 0.1 molar.

In aqueous solutions, hydrochloric acid dissociates into hydrogen and chloride ions.

HCl $\to$ ${H}^{+}$ + $C {l}^{-}$

Because there is a one to one ratio between the acid and the hydrogen ion, the $\left[{H}^{+}\right]$ is 0.1 molar.

Now convert the hydrogen ion concentration to pH using the equation pH = -log $\left[{H}^{+}\right]$

Applying this to our problem

pH = -log $\left[{H}^{+}\right]$
pH = -log [0.1]
pH = 1

To reverse the problem from pH to [H+]
Use the equation
[H+] = antilog(-pH)