1. Acids
and
Bases

2. Acids and Bases
Some of our favorite foods make our tongue curl up because they are SOUR.

3. Bitter!
Some foods have a “bite” of their own because they’re somewhat bitter.
WHY?

4. Acidic/Basic There is a scientific reason for this:
These foods are either acidic or basic.
Other substances besides foods have these characteristics.

5. Acids and Bases Chemicals may be classed as acids or bases.
Things that are neither acids nor bases are neutral.
pH measures how acidic or basic a solution is.

6. Acids Often taste sour Strong acids can burn skin & eyes
Strong acids can dissolve metals
Examples:
Lemon juice
Vinegar
Car battery acid (dangerous!)

7. Bases Can taste bitter, sweetish, or salty
Strong bases can burn skin & eyes
Bases react more easily with protein than with metal; they are often used for cleaning
Examples:
Milk
Baking soda
Soap
Drain cleaner (dangerous!)

8. Some substances are not really an acid or a base: For example, pure water

9. The Nomenclature of
ACIDS
Acids are easy to recognize as compounds as they begin with the element hydrogen. As with other ionic bonds, acids fall into 2 categories, binary and ternary.

10. The Nomenclature of
ACIDS
Examples of binary acids would include things like:
HF, HI, H2S and HCl
Examples of ternary acids would include things like:
H2SO4 and HNO3

11. The Nomenclature of
ACIDS
Naming of binary acids
Step 1:Name the anion, changing the ending to “-ic”
Step 2: Add the prefix “hydro-”
Step 3: Slap acid on the end

12. “hydroflouric acid” The Nomenclature of ACIDS Example #1: HF
“fluorine” becomes
“fluoric” becomes
“hydrofluoric” becomes
“hydroflouric acid”

13. Naming of ternary acids
The Nomenclature of
ACIDS
Naming of ternary acids
Step 1:Name the polyatomic
Step 2: Change “-ate” to “-ic”
or “-ite” to “-ous”
Step 3: Slap acid on the end

14. “sulfuric acid” The Nomenclature of ACIDS Example #1: H2SO4
“sulfate” becomes
“sulfuric” becomes
“sulfuric acid”

15. Rules for Writing Formulas for binary acids
The Nomenclature of
ACIDS
Rules for Writing Formulas for binary acids
Step 1: Does the name begin with
“hydro-”? If yes, then…
Step 2:Write the symbol for the
hydrogen ion followed by the
symbol for the second element
Step 3: Crisscross the charges and write them as subscripts.

16. The Nomenclature of ACIDS
Rules for Writing Formulas for binary acids
Example: hydrosulfuric acid

17. The Nomenclature of ACIDS
Rules for Writing Formulas for binary acids
Example: hydrosulfuric acid
H S-2

18. The Nomenclature of ACIDS
Rules for Writing Formulas for binary acids
Example: hydrosulfuric acid
H S-2

19. H2S The Nomenclature of ACIDS Example: hydrosulfuric acid H+1 S-2
Rules for Writing Formulas for binary acids
Example: hydrosulfuric acid
H S-2
H2S

20. Rules for Writing Formulas for ternary acids
The Nomenclature of
ACIDS
Rules for Writing Formulas for ternary acids
Step 1: Does the name begin with
“hydro-”? If no, then…
Step 2:Write the symbol for the
hydrogen ion followed by the
appropriate polyatomic ion
Step 3: Crisscross the charges and write them as subscripts.

21. Rules for Writing Formulas for binary acids Example: sulfuric acid
The Nomenclature of
ACIDS
Rules for Writing Formulas for binary acids
Example: sulfuric acid

22. Rules for Writing Formulas for binary acids Example: sulfuric acid
The Nomenclature of
ACIDS
Rules for Writing Formulas for binary acids
Example: sulfuric acid
H SO4-2

23. Rules for Writing Formulas for binary acids Example: sulfuric acid
The Nomenclature of
ACIDS
Rules for Writing Formulas for binary acids
Example: sulfuric acid
H+1 SO4-2
H+1 SO4-2

24. Rules for Writing Formulas for binary acids Example: sulfuric acid
The Nomenclature of
ACIDS
Rules for Writing Formulas for binary acids
Example: sulfuric acid
H+1 SO4-2
H+1 SO4-2
H2SO4

25. The Nomenclature of ACIDS
Name the chemical or write the symbol
1. HI
2. phosphoric acid
3. hydrobromic acid
4. H2SO3

26. The Nomenclature of ACIDS
Name the chemical or write the symbol
hydroiodic acid 1.
2. phosphoric acid
3. hydrobromic acid
4. H2SO3

27. The Nomenclature of ACIDS
Name the chemical or write the symbol
hydroiodic acid 1. 2.
3. hydrobromic acid
4. H2SO3
H3PO4

28. The Nomenclature of ACIDS
Name the chemical or write the symbol
hydroiodic acid 1. 2. 3.
4. H2SO3
H3PO4
HBr

29. The Nomenclature of ACIDS
Name the chemical or write the symbol
hydroiodic acid 1. 2. 3. 4.
H3PO4
HBr
sulfurous acid

30. pH Scale We use this scale to measure the strength of an acid or base.
pH is defined as the –log[H+]
pH can use the concentration of hydronium ions or hydrogen ions.

31. 7
Acid
Base
pH Scale 14
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 515

32. pH of Common Substances
Timberlake, Chemistry 7th Edition, page 335

33. The pH Scale pH scale ranges from 0 -14
pH 7 is neutral; neither acid nor base
Pure water is pH 7
Low pH (0-6.9) = acid
High pH (7.1-14) = base
The closer to the ends of the scale, the stronger the solution is

34. 0--------------7---------------14
Acid
Any substance which has a pH of value of less than 7 is considered an acid
Acid Neutral Base

35. 0--------------7---------------14
Base
Any substance which has pH value greater than 7 is a base
Acid Neutral Base

36. pH 7 A pH of 7 is called neutral—neither acid nor base.
Acid Neutral Base

37. The pH Scale Each pH unit is 10 times as large as the previous one
A change of 2 pH units means 100 times more basic or acidic
x10
x100

38. The pH Scale Careful measurement is important
A mistake of one pH unit means 10 times too much or too little!
x10
x100

39. How Do We Measure pH?
One way to measure pH is by using special strips of paper called pH paper

40. How Does It Work?
The paper is treated with chemicals (indicators) that change color to show the pH.
When the paper touches the substance being tested, it turns a specific color to tell if the substance is an acid or a base.

41. To Use pH Paper Place the edge of the pH paper into the mixture.
Observe the color change of the pH paper
Match the resulting color to the colors listed on the outside of the pH paper package.
The colors match with a correlated pH number.
The number is the pH value of the sample.

42. Historical views on acids
The Oldest Theory is the Arrhenius Theory

43. Arrhenius looked at the substances which were called acids
Arrhenius looked at the substances which were called acids. Some of these substances were known from even before the days of alchemy.
They taste sour, turn blue litmus to red, neutralize bases, release hydrogen gas when added to an active metal and release carbon dioxide when added to a carbonate.
Arrhenius said these properties were due to the production of H+ ions when acids dissolve in water.

44. He looked at the properties of bases
He looked at the properties of bases. They taste bitter, feel slippery (soapy), turn red litmus blue and neutralize acids.
Arrhenius said these properties were due to the production of OH- ions when bases are dissolved in water.

45. Historical views on acids
O2 found in oxyacids (e.g. H2SO4) was originally thought to cause acidic properties. Later, H2 was implicated, but it was still not clear why CH4 was neutral.
Arrhenius made the revolutionary suggestion that some solutions contain ions & that acids produce H2+ ions in solution. + H O H O Cl Cl H + +
Ionization

46. Historical views on acids
The more recent Bronsted-Lowry concept is that acids are H+ (proton) donors and bases are proton acceptors + H O H O Cl Cl H + +

47. The Bronsted-Lowry concept
In this idea, the ionization of an acid by water is just one example of an acid-base reaction. + Cl H O
acid
base
conjugate acid
conjugate base
conjugate acid-base pairs
Acids and bases are identified based on whether they donate or accept H+.
“Conjugate” acids and bases are found on the products side of the equation. A conjugate base is the same as the starting acid minus H+.

48. The Bronsted-Lowry concept
Today we know that a bare proton does not exist in water, it forms a chemical bond with a water molecule forming the H3O+. This ion is called the hydronium ion.
H2O   H3O+ + OH-
“Pure” water is always a dynamic mixture
of these three substances in equilibrium

49. The Bronsted-Lowry concept
1) A B/L acid is the species which donates a proton in a proton transfer reaction. What is meant by a proton here?
2) A B/L base is the species which _________ .
3) A B/L acid is the species which _________

50. HCl(aq) + H2O(l)  H3O+(aq) + Cl-(aq)
4) A specific strong acid - base reaction:
HCl(aq) + H2O(l)  H3O+(aq) + Cl-(aq)
HCl(aq) is the ___________________ .
H2O(l) is the ________________ .
H3O+(aq) is the ________________________.
Cl-(aq) is the _________________________ .

51. CH3COOH is the _____________________.
H2O is the _________________________.
H3O+ is the ____________________.
CH3COO- is the _____________________.

52. Practice problems
Identify the acid, base, conjugate acid, conjugate base, and conjugate acid-base pairs:
HC2H3O2(aq) + H2O(l)  C2H3O2–(aq) + H3O+(aq)
acid
base
conjugate base
conjugate acid
conjugate acid-base pairs
OH –(aq) + HCO3–(aq)  CO32–(aq) + H2O(l)
base
acid
conjugate base
conjugate acid
conjugate acid-base pairs

53. OYO Practice 1. HF(aq) + SO32–(aq) 2.CO32–(aq) + HC2H3O2(aq)
3. H3PO4(aq) + OCl –(aq)

54. Answers: OYO Practice 1. HF(aq) + SO32–(aq)  F–(aq) + HSO3–(aq) acid
base
conjugate base
conjugate acid
conjugate acid-base pairs 2.
CO32–(aq) + HC2H3O2(aq)  C2H3O2–(aq) + HCO3–(aq)
base
acid
conjugate base
conjugate acid 3.
conjugate acid-base pairs
H3PO4(aq) + OCl –(aq)  H2PO4–(aq) + HOCl(aq)
acid
base
conjugate base
conjugate acid
conjugate acid-base pairs

55. Reaction Types HCl + NaOH  NaCl + H2O HCl + NaOH  NaCl + H2O
Neutralization Reaction – a special double replacement reaction in which an acid is combined with a base and yields water and a salt.
HCl + NaOH  NaCl + H2O
HCl + NaOH  NaCl + H2O

56. Titrations
In a titration a solution of accurately known concentration is added gradually added to another solution of unknown concentration until the chemical reaction between the two solutions is complete.
End point – the point at which the reaction becomes complete
Equivalence point – the point at which the reaction is neutral
Indicator – substance that changes color at (or near) the
equivalence point
Slowly add base
to unknown acid
UNTIL the indicator
changes color
4.7

57. Ma x Va = Mb x Vb What volume of a 1.420 M NaOH solution is
Required to titrate mL of a 4.50 M H2SO4
solution?
WRITE THE CHEMICAL EQUATION!
H2SO4 + 2NaOH H2O + Na2SO4
Ma x Va = Mb x Vb