1. 4.11: pH and pOH
Chemistry 12

2. 4.11
Math Review
Log 10(1000)= 3
103 = 1000

3. 4.11
Math Review
Log 10(1000)= 3
103 = 1000

4. 4.11 pH scale Tells us if solution is acidic, basic or neutral
Is calculated using [H3O+]
Is an easier way to communicate [H3O+]
Water has a pH of seven
The concentration of the hydronium ion in water is 1.0 x 10-7

5. 4.11
pH formula pH = -log [H3O+]

6. In pH, only digits after the decimal are considered significant
4.11
E.g. What is the pH of M HCl?
pH = -log [H3O+]
pH = -log [0.0035]
pH =
= 2.46
In pH, only digits after the decimal are considered significant

7. 4.11
What is pOH of last example? pH + pOH =14 14 – pH = pOH 14 – = 11.54

8. 4.11
E.g. What is [H3O+] of a solution with a pH of 11.50? [H3O+] = 10(-pH) [H3O+] = 10(-11.50) = x = 3.2 x 10-12
2 sig figs
2 sig figs

9. Recall: pH =11.50 & we calculated [H3O+]
4.11
[OH-] of last example? (2 possible ways) [OH-] = Kw/ [H3O+] = 1.0 x 10-14/ x = 3.2 x 10-3 pOH = 14 – = 2.50 [OH-] = 10(-pOH) = 10(-2.50)
Recall: pH =11.50 & we calculated [H3O+]

10. 4.11
Summary

11. [H3O+] [OH-] pOH pH Kw = [H3O+]=10-pH [OH-][H3O+] pH = -log [H3O+]
14= pH+ pOH
pOH
= -log [OH-]

12. Calculations Assignment (p. 12-19)
4.11
Read & Highlight
Calculations Assignment (p )
Hebden # 47-57