Ways to measure Acidity/Basicity What is pH? What is pOH? pH and pOH Ways to measure Acidity/Basicity What is pH? What is pOH?

What is pH? pH = potential Hydrogen The pH scale measures how acidic or basic a substance is, is logarithmic The pH scale ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic, greater than 7 is basic.

Basic Equations pH + pOH = 14 Kw = [H+] [OH-] = 1 x 10 -14

Calculating pH Values pH = 14 – pOH pH = - log [H+] Example: Calculate pH given [H+] = 1.4 x 10-5 M pH = - log [H+] pH = - log [1.4 x 10-5] pH = 4.85

Calculating [H+] values EXAMPLE: Find [H+] if pH = 8.5 [H+] = 10-pH 
[H+] = 10-8.5 
[H+] = 3.2 x 10-9 M

Calculating pOH pOH = 14 – pH pOH = -log[OH-] EXAMPLE: What is the pOH of a solution that has a hydroxide ion concentration of 4.82 x 10-5 M ? pOH =  - log [OH-] pOH =  - log [4.82 x 10-5] pOH = 4.32

YOU TRY! pH = 4 7.1 = -log [H+] 10 – 7.1 = [H+] = 7.9 x 10-8 M   Find the pH of the solution if [H+] = 1 x 10-4 M What is the hydrogen ion concentration if pH = 7.1? What is the pH if [OH-] = 4 x 10 -11 M? pH = 4 7.1 = -log [H+] 10 – 7.1 = [H+] = 7.9 x 10-8 M pOH = -log [OH-] pOH = -log [4 x 10 -11 ] =