1. pH

2. pH Scale pH is a measure of how acidic or basic a solution is.
Potential for Hydrogens (H+)
ranges from 0 to 14.
Acidic solutions have pH < 7
pH = 7 is neutral
Pure water has a pH of 7.
Basic solutions: pH > 7.

3. pH Scale
A change of 1 pH unit represents a tenfold change in the acidity of the solution.
For example, if one solution has a pH of 1 and a second solution has a pH of 2, the first solution is not twice as acidic as the second—it is ten times more acidic.

4. pH
Since the concentrations of H+ ions are small numbers expressed in scientific notation, it is easier to express the concentration using pH
pH = -log [H+]
Acid: pH <7
Neutral : pH = 7
Base: pH > 7

5. Practice Problem
How would you characterize a solution of seawater that has a pH of 8?

6. Practice Problem
If a solution has a hydrogen ion concentration of 1.0 x M, what is the pH of the substance?

7. Measuring pH Litmus paper pH paper Acid-base indicators pH probe
Acids cause blue litmus paper to turn red
Bases cause red litmus paper to turn blue
pH paper
Acid-base indicators
Chemical dyes whose colors are affected by acidic or basic solutions
pH probe

8. Practice Problem
A substance is tested using both red and blue litmus paper, the results are listed in the table below. Would you characterize the solution as acidic, basic or neutral?
Paper type
Color of paper
Red litmus
red
Blue litmus