1. Aim # 30: What is the pH of a solution?
H.W. # 30
Study pp Study class notes Ans. ques. p. 534 # 52, p. 533 # 30a,c d c,d and 34a,b

2. I The pH scale 0 7 14 increasing acidity neutral increasing basicity
The pH of a solution indicates the concentration of hydrogen ions in the solution.
If pH < solution is acidic
If pH = solution is neutral
If pH > solution is basic

3. Some pH values of common liquids
lemon juice vinegar carbonated drinks grapefruit juice orange juice tomato juice rainwater milk pure water blood seawater milk of magnesia

4. II The autoionization of water
H2O(l) H+(aq) + OH-(aq)
If OH- ions are added to the water, how would the equilibrium be affected?
How would [H+] be affected?
If H+ ions are added instead, how would [OH-] be affected?
Keq = [H+][OH-] [H2O]
What is the molar concentration of H2O?

5. Keq x [H2O] = [H+][OH-] Kw
Kw = [H+][OH-] = 1.0 x 10-14
What is the value of [H+] in pure water? [OH-]?
[H+] = [OH-] = 1.0 x 10-7 mol/L in pure H2O at 250C.
If [H+] > 1.0 x the solution is acidic. What does this imply about [OH-]?
If [H+] > [OH-] (acidic) If [OH-] > [H+] (basic)

6. Ans. [H+] = 4.00 x 10-3 [OH-] = Kw/[H+] = 1.00 x 10-14 4.00 x 10-3
Problem: The [H+] of a solution is 4.00 x 10-3M What is [OH-]? Is the solution acidic, neutral, or basic?
Ans. [H+] = 4.00 x [OH-] = Kw/[H+] = x x 10-3
[OH-] = x mol/L = 2.50 x 10-12mol/L
[H+] > 1.00 x 10-7 > [OH-] Therefore, the solution is acidic.

7. Problem: The [OH-] of a solution is 1. 25 x 10-9M. Calculate [H+]
Problem: The [OH-] of a solution is 1.25 x 10-9M. Calculate [H+] Is the solution acidic, neutral, or basic?
Ans. [H+] = Kw/[OH-] = 1.00 x x [H+] = 8.00 x 10-6 > 1.00 x 10-7 mol/L
The solution is acidic.

8. Problem: If [H+] is 6.2 x 10-8, what is the [OH-]?
Ans.
[OH-] = Kw/[H+] = 1.0 x x [OH-] = .16 x 10-7 = 1.6 x 10-8 mol/L

9. III pH is the negative logarithm of the hydrogen ion concentration of a solution pH = - log [H+] or [H+] = 10-pH
Problem: If [H+] of a solution is 1.0 x 10-5, what is the pH of the solution? Is it acidic, neutral, or basic?
Ans: pH = - log [H+] pH = - log (1.0 x 10-5) pH = - (log log 10-5) pH = - ( ) pH = pH < The solution is acidic.

10. Problem: What is the hydrogen ion concentration of a solution with a pH of 9?
Ans: pH = - log [H+] = log [H+] = [H+] = 10-9 = 1.0 x 10-9 mol/L
Problem: What is the pH of a solution in which [H+] = 3.0 x 10-10? What is the [OH-]?
Ans: pH = -log(3.0 x 10-10) = 9.5
[OH-] = (1.0 x 10-14)/(3.0 x 10-10) [OH-] = 3.3 x 10-5

11. The pH scale
pH [H+] [OH-] or
or 1

12. Problem: What is the pOH of a 0.10 M solution of NaOH?
IV pOH is the negative logarithm of the hydroxide ion concentration of a solution pOH = - log [OH-] or [OH-] = 10-pOH
Problem: What is the pOH of a 0.10 M solution of NaOH?
Note: Kw = [H+][OH-] = 1.0 x log kw = log [H+] + log [OH-] = log kw = -log [H+] – log [OH-] = 14
pKw = pH + pOH = 14

13. Problem: The pOH of a solution is 10. What is its pH
Problem: The pOH of a solution is What is its pH? What are the [OH-] and [H+]?
Ans: pH = 14 – pOH = 14 – 10 = 4
[OH-] = 1.0 x 10-10M
[H+] = 1.0 x 10-4M