1. Chapter 19
Acids & Bases

2. Properties of Acids and Bases
Acids are sour (do not taste)
e.g. Lemon juice and vinegar are both aq solns of acids.
Bases taste bitter.
Bases have a slippery feel. (not a safe chem test)

3. Definitions of Acid and Bases
Acids: H+ donating substances e.g. HCl → H+ + Cl-
Bases: H+ accepting substances.

4. Rxns with Metals and Carbonates
Simple tests that distinguishes acids from bases
1. the rxn of acids with carbonate ions (CO32- )or
hydrocarbonate ions, (HCO3-), to form CO2 gas,
water, and another cpd.
e.g. HCl (aq) + Na2CO3 → CO2 + H2O + 2NaCl
e.g. HCl(aq) + NaHCO3 → NaCl(aq) + CO2 + H2O
bases do not react with carbonates and …

5. Rxns with Metals and Carbonates
2. Add a small piece of metal (above H in the activity series of metals) in an acid, hydrogen gas bubbles will be formed. 2HCl(aq) + Mg(s) → MgCl2(aq) + H2(g) ** no rxn with bases.

6. Submicroscopic Behavior of Acids
The simplest definition of an acid
a sub that produces (H+) when it dissolves in water.
Acidity of a soln depends on the [H+] in the soln

7. Submicroscopic Behavior of Acids
e.g. HCl(g) is an acid as
it produces H+ when dissolved in water. HCl(aq)
Hydrochloric acid

8. Acidic Hydrogen Atoms
In an acid, any H atom that can be transferred to H2O is called an acidic hydrogen.
e.g. HCl, HNO3, H2SO4, CH3COOH
Can’t be transferred
HC2H3O2

9. Acidic Hydrogen Atoms
To help distinguish acids from other H-containing molecules, acidic H are written first in the formula.
e.g. HCl(aq), HNO3(aq) , H2SO4 (aq)

10. Monoprotic Acids Acetic Acid Hydrochloric acid Monoprotic acids
CH3COOH HCl
Acetic Acid Hydrochloric acid
Monoprotic acids
only 1 acidic H.
H2SO4
Sulfuric acid
a diprotic acid
H3PO4
Phosphoric acid
a triprotic acid

11. Submicroscopic Behavior of Bases
A base
a subs that produces, OH –, when dissolves in H2O.
e.g. NaOH (aq) → Na OH-
Hydroxide ion
ionization
ionic
covalent
Acids, Bases, salts, ionic cpds (dissolved) are electrolytes (polar)

12. all (100% turns into ions in water).
Strong Acids and Bases
NaOH is a strong base because
all (100% turns into ions in water).
NaOH(aq) → Na+ (aq) OH- (aq)
All ions
No un-ionized NaOH
‘strong’ ≠ high [ ]
10 M HCl(aq) is not stronger than 0.1M HCl(aq)
The ionization of the base is complete.

13. Strong and Weak Acids Hydrochloric acid Acetic acid Sulfuric acid
Strong Acids
Weak Acids
Hydrochloric acid
Acetic acid
Sulfuric acid
Carbonic acid H2CO3
Nitric acid
Not 100% ionized
CH3COOH(s) CH3COO−(aq) H+(aq)
weak
< 10% most
HCl(g) → H+ (aq) Cl- (aq)
strong
100%

14. NH3(g) + H2O (l) NH4+(aq) + OH−(aq)
Strong and Weak Bases
Strong Bases
Weak Bases
Sodium hydroxide
Ammonia (NH3; NH4OH)
Potassium hydroxide
Aluminum hydroxide
<10% ionized
NH3(g) + H2O (l) NH4+(aq) + OH−(aq)
NaOH(aq) → Na+ (aq) OH- (aq)
100% ionized

15. Strong Bases strength of a base
based on the % of units ionized, not the # of OH– ions produced. ([OH-])
e.g. NaOH ionizes 100%; about 10% of NH4OH ionizes (about 90% remains as molecules)

16. HCl(g) + H2O(l) → H3O+(aq) + Cl−(aq)
Strong Acids
HCl(g) + H2O(l) → H3O+(aq) + Cl−(aq)
HCl is a strong acid because it ionizes completely.
no un-ionized HCl molecules are in a aq soln of HCl. i.e. 100 % ionized.

17. Weak Acids Acetic acid, CH3COOH, is a weak acid.
CH3COOH ↔ CH3COO- + H+
Unionized molecules
ions
Partially ionizes
A soln of weak acid contains a mixture of un-ionized acid molecules, H3O+ and ….

18. Weak Acids The [ ] of the un-ionized acid is always the greatest.

19. Weak Bases
NH3 is a weak base because most of its molecules do not react with H2O to form ions.
NH3 (g) + H2O (l) NH4+ (aq) + OH- (aq)
Un-ionized molecules
ions
Other examples: Al(OH)3, and Fe(OH)3.

20. Strength Is Not Concentration
Strength concentration
weak and strong : compare the strengths of acids and base (degree of ionization).
dilute and concentrated :describe the [ ] of solns. (molarity)
The combn of strength and [ ] ultimately determines the behavior of the soln.

21. Strength ≠ Concentration
e.g. a 10 M CH3COOH(aq).
A conc weak acid
e.g M NaOH (aq)
A dilute strong base

22. The pH Scale pH
a math scale in which the [H+] in a soln is expressed as a # from 0 to 14.

23. Measuring pH Indicators register different colors at different pHs.
pH meters are instruments that measure the exact pH of a soln.

24. Interpreting the pH Scale
pH of 7 is neutral,
A pH < 7 is acidic,
a pH > 7 is basic.

25. pH of Common Materials

26. Types of Acid-Base Reactions
Neutralization rxn
The rxn of an acid and a base to produce a salt and water only.
NaOH(aq) + HCl(aq) → NaCl(aq) + H2O (l)
Mg(OH)2(aq) + H2SO4(aq) → MgSO4(aq) + H2O (l)

27. Salt Hydrolysis
pH of a salt solution
pH = 7
pH < 7
pH > 7

28. CST example 1
Equal volumes of 1 M hydrochloric acid (HCl) and 1 M sodium hydroxide base (NaOH) are mixed. After mixing, the soln will be
A strongly acidic
B weakly acidic
C nearly neutral
D weakly basic

29. CST example 2
Which of the following is an observable property of many acids?
A they become slippery when reacting with water.
B they react with metals to release hydrogen gas.
C they produce salts when mixed with other acids.
D they become more acidic when mixed with a base.

30. CST example 3
Potassium hydroxide (KOH) is a strong base because it
A easily releases hydroxide ions.
B does not dissolve in water.
C reacts to form salt crystals in water.
D does not conduct an electric current.

31. CST example 4
Of four different laboratory solutions, the solution with the highest acidity has a pH of
A 11
B 7
C 5
D 3

32. CST problem 5
Which would be most appropriate for collecting data during a neutralization rxn?
A a pH probe
B a statistics program
C a thermometer
D a graphing program

33. CST problem 6
Copper (II) nitrate and sodium hydroxide solns react in a test tube as shown below.
Cu(NO3)2(aq) + 2NaOH(aq) Cu(OH)2(s) + 2NaNO3(aq)
If nitric acid is added to the test tube, the amt of (s) ppt decreases. The best explanation for this is that the acid
A dilutes the soln making the ppt dissolve.
B reacts with the copper (II) nitrate, pushing the eqm to the left.
C will dissolve most solids, including sodium nitrate.
D will react with the copper (II) hydroxide to form water and soluble copper (II) nitrate.

34. The End