## Definition

Let's start this tutorial by clarifying the equation for determining the pH of a solution.

The pH of a solution is defined as the negative base 10 logarithm (log _{10}) of the concentration of the reaction of H^{+} with a water molecule to produce a hydroxonium ion (H_{3}O^{+}).

**Equation 1 : pH= -log[H _{3}**

**0**

^{+}**]**