1. Acids and Bases

2. General properties ACIDS Taste sour Turn litmus
React with active metals – Fe, Zn
React with bases
BASES
Taste bitter
Turn litmus
Feel soapy or slippery (react with fats to make soap)
React with acids
blue to red
red to blue

3. More properties ACIDS Feel and look like water
Conduct electricity (electrolytes) when dissolved in water
Burn or sting
Usually formula starts w/ H
BASES
do not react with metals
Can be strong or weak electrolytes in water
Do not sting or burn

4. Definitions Acids – produce H+ Arrehenius Bases - produce OH-
Acids – donate H+
Bases – accept H+
Arrehenius
only in water
Bronsted-Lowry
any solvent

5. Why is H+ a proton? *H is made of 1 proton and 1 electron
*When H loses an e-, all that is left is a proton.

6. Examples The hydrogen ion in aqueous solution
H H2O  H3O+ (hydronium ion)
Examples
Arrhenius
HCl
NaOH
Bronsted-Lowry
HCl
HCN
NH3

7. Conjugate acid/base pairs
Conjugate acid –acid that forms after the original base accepts an H+
Conjugate base –base that forms after the original acid donates an H+
NH3(aq) + H2O(l)  NH4+(aq) + OH-(aq)

8. Conjugate acid/base pairs
**Notice how water is an ACID in the first reaction and BASE in the other reaction
*water is called AMPHOTERIC

9. Show how water can be amphoteric.
Water is a mixture of H2O, H+ and OH-

10. The Bronsted-Lowry Concept
Conjugate pairs
HCl Cl-
CH3COOH CH3COO-
NH NH3
HNO3 NO3-
How does a conjugate pair differ?
H+ transfer

11. Neutralization HCl + NaOH  NaCl + HOH HCl + Mg(OH)2 
In general: Acid Base  Salt + Water
All neutralization reactions are double displacement reactions.
HCl NaOH  NaCl HOH
HCl Mg(OH)2 
H2SO NaHCO3 

12. Let’s examine the behavior of an acid, HA, in aqueous solution.
CHM 101
Let’s examine the behavior of an acid, HA, in aqueous solution.
Sinex HA
What happens to the HA molecules in solution?

13. 100% dissociation of HA HA H+ Strong Acid A-
Would the solution be conductive?

14. Partial dissociation of HA
Weak Acid A-
Would the solution be conductive?

15. At any one time, only a fraction of the molecules are dissociated.
HA  H A- HA H+
Weak Acid A-
At any one time, only a fraction of the molecules are dissociated.

16. Strong and Weak Acids/Bases
Strong acids/bases – completely dissociates into
ions
HCl NaOH
HNO3 KOH
H2SO4
Weak acids/bases – only partial dissociation, both ions and molecules
CH3COOH NH3

17. Calculations ↕ OH- ↔ pOH 4 different values to find:
pH (this indicates if it’s ACID/BASE/NEUTRAL)
pOH
H+ (hydrogen ions) or H3O+ (hydronium ions)
OH- (hydroxide ions)
H+ ↔ pH ↕
OH- ↔ pOH

18. Calculations
What is pH? The power of hydrogen (used to determine if solution is and acid, base or neutral)
What is pOH? The power of hydroxide
What is [H+]? The molarity of acid ions in a solution
What is [OH-]? The molarity of base ions in a solution

19. pH = -log[H3O+]* pOH = -log[OH-] pH + pOH = 14
*or [H+]
pOH = -log[OH-]
pH + pOH = 14

20. [H+]= 10^(-pH) [OH-] = 10^(-pOH)
How to check your work:
[H3O+][OH-] = 1.0  10-14
pH + pOH = 14

21. pH of Common Substances

22. What is the pH of 0.050 M HNO3? pH = -log[H3O+] pH = -log[0.050]
Acidic or basic?
Acidic

23. Example
Find the pH, pOH, & [OH- ] if [H+]= 3.25x10-4 M

24. What is the molarity (concentration) of HBr in a solution that has a pOH of 9.6?
pH + pOH = 14
pH = 14
pH = 4.4
pH = -log[H3O+]
4.4 = -log[H3O+]
-4.4 = log[H3O+]
[H3O+] = 4.0  10-5 M HBr
Acidic

25. pH pOH [H+] [OH―] Acid/Base /Neutral
3.21
5.87
2.51 x M M

26. Testing pH in the Lab
Litmus paper
Indicators
pH meter

27. Indicators
dyes that will change color in the presence of an acid or base.
Color changes occur when the molecules are ionized (acting as an acid) or un-ionized (acting as a base).
Indicators change color during specific pH ranges

28. Some of the many pH Indicators and their pH range

29. Titration
A laboratory method for determining the concentration of an unknown acid or base using a neutralization reaction.
A standard solution,(a solution of known concentration), is used.

30. Titration Terminology
Equivalence point - The point at which there are equal concentrations of acid and base.
[H+] = [OH-]
End point – the point at which the chosen indicator changes color to mark a change in pH (also called indication point)

31. Equivalence Point

32. Solving Titration Problems
Use the titration formula
MaVa = MbVb
What is the concentration of HCl if 30.0 mL of 0.10 M NaOH neutralizes 50.0mL HCl?