The tutor introduces and defines pH, an important concept in chemistry.

Most people know that neutral pH is 7. However, what is pH really, and what is it based on?

pH is defined as follows:

pH = -log[H⁺]

Here’s an example:

Find the pH of a 0.0035M solution of HNO₃

Solution:

First, we write the dissociation equation:

HNO₃→H⁺(aq)+NO₃^–(aq)

Since HNO₃ is a strong acid, it completely dissociates. Thus, [H⁺]=0.0035M.

pH = -log[H⁺] = -log(0.0035) = 2.45593 or 2.5 (sig. digits).

HTH:)

Source:

Hebden, James A. Chemistry: Theory and Problems, Book Two. Toronto: McGraw-Hill
Ryerson Limited, 1980.

Chemistry: pH