1. Chapter 18
Acids and Bases

2. Properties of Acids and Bases
Physical properties:
Acids: taste sour, conduct electricity
Bases: taste bitter, feel slippery, conduct electricity

3. Chemical properties Acids: turn litmus paper red
Bases: turn litmus paper blue

4. The Arrhenius Model Acids – produce hydrogen ions in aqueous solution
HCl H+ + Cl-
Bases – produce hydroxide ions in aqueous solution
NaOH  Na+ + OH-

6. The Bronsted-Lowry Model
Arrhenius concept is limited because it only allows for one kind of base
Acid – proton donor
Base – proton acceptor

7. General reaction for a Bronsted-Lowry acid dissolving in water:
Conjugate acid-base pair – two substance related to each other by the donating and accepting of a single proton

8. Identify the acid, base, conjugate acid, and conjugate base in the following:
HCO H2O  CO H3O +1

9. Water as an Acid and a Base
Amphoteric substance – can behave either as an acid or as a base
Ionization of water:
One water molecule acts as an acid donating protons, one acts as a base accepting protons

10. Strengths of Acids and Bases
Strong acids and bases ionize completely
Weak acids and bases ionize only partially

12. A strong acid contains a relatively weak conjugate base, one that has a low attraction for protons
A weak acid contains a relatively strong conjugate base

13. Hydrogen and Hydroxide Ions and pH
Acidity or Basicity of a substance is related to the concentration of hydrogen and hydroxide ions in that substance

14. The product of [H+] and [OH-] is always constant
Kw = ion product constant for water
No matter what the solution contains, Kw will always equal 1.0 x 10-14

16. Calculate the [H+] or [OH] and state whether the solution is neutral, acidic, or basic
1.0 x 10-5 M OH-
1.0 x 10-7 M OH-
10.0 M H+

17. Determining the Acidity of a Solution
The pH Scale: 0 – 14
<7 = acidic
7 = neutral
>7 = basic

19. A mathematical scale in which the concentration of H+ ions in a solution is expressed as a number from 0 – 14
pH = log [H+]

20. What is the pH of solutions having the following ion concentrations?
[H+] = 1.0 x 10-2 M
[H+] = 3.0 x 10-6 M

21. Because the pH scale is a log scale based on 10, the pH changes by 1 for every power of 10 change in the [H+]

22. Log scales similar to the pH scale are used for representing other quantities:
pOH = log [OH]

23. What is the pOH of a solution having the following ion concentration?
[OH-] = 1.0 x 10-6 M
[OH-] = 6.5 x 10-4 M

24. pH + pOH = 14 What is the pOH of a solution whose pH is 5?
What is the pH of a solution whose [OH-] = 4.0 x 10-3 M

25. Calculate the pH and pOH of the following solutions:
[H+] = M
[OH-] = M

26. It is also possible to find the [H+] or [OH-] from the pH or pOH by undoing the log operation
[H+]= 10-pH
[OH-] = 10-pOH

27. The pH of a human blood sample was measured to be 7. 41
The pH of a human blood sample was measured to be What is the [H+] and [OH-]in this blood?

28. Neautralization Reactions
Acid + Base  salt + water
HCl + NaOH  NaCl + H2O
Ionic:
Net ionic:

29. Titration
Method for determining the concentration of a solution by reacting a known volume of that solution with a solution of known concentration.
If unknown is acid, known must be base

30. Titration procedure
Measured volume of acid or base of unknown concentration is placed in a flask and initial pH is recorded
Buret is filled with the solution of known concentration (standard solution/titrant)
Standard solution added slowly until neutral pH is reached (equivalence point)
[H+] = [OH-]

32. End point of a titration can be measured using a pH meter or an indicator
Indicator changes color at different pH values

33. Titration curve (pH curve) – plot of pH vs volume of titrant added

34. A volume of 18. 28 mL of a standard soluiton of 0
A volume of mL of a standard soluiton of M NaOH was required to neutralize mL of a solution of nitric acid. What is the concentration of the nitric acid?

35. Buffered Solutions
Solutions that resist changes in pH when acids or bases are added
Weak acid + conjugate base
HF + NaF