1. pH Scale Definition of Acids and Bases
-Acids and bases are defined in several different ways, but the most definitive way is based on the pH scale
-pH stands for the percentage of hydrogen, although some think it could mean power of hydrogen
-The pH scale is a measurement of the concentrations of hydrogen ions in solution and the acidic or basic nature of the solution

2. pH Scale
-The pH scale ranges from below 0 (very acidic) to above 14 (very basic).
-pH values less than 7 are considered acidic and those greater than 7 are considered basic. 7 itself is neutral.
-The scale is not linear but logarithmic, meaning that at pH 2, for example, the concentration of hydrogen ions is ten times greater than it is at pH 3.

3. pH Scale

4. pH Scale Calculations Calculating pH
-pOH is a concentration of the hydroxide ions which, for certain bases, is relative to the amount of hydrogen ions present
pH = 14 – pOH
14 = pH + pOH
[H+] = concentration of H+; usually measured in molarity
[OH-] = concentration of OH-; usually measured in molarity
pH = - log [H+] 10-pH = [H+]
pOH = - log [OH-] 10-pOH = [OH-]

5. pH Scale Calculations

6. pH Scale Practice 1. Find the pH of a 0.0025 M HCl solution.
2. What is the hydrogen ion concentration in a solution that has a pH of 8.34?
3. A solution has a pOH of What is the pH of this solution?