1. Acids & Bases

2. Electrolytes vs. Nonelectrolytes
The ammeter measures the flow of electrons (current)
through the circuit.
If the ammeter measures a current, and the bulb
glows, then the solution conducts.
If the ammeter fails to measure a current, and the
bulb does not glow, the solution is non-conducting.

3. Definition of Electrolytes and Nonelectrolytes
An electrolyte is:
A substance whose aqueous solution conducts
an electric current.
A nonelectrolyte is:
A substance whose aqueous solution does not
conduct an electric current.
Try to classify the following substances as
electrolytes or nonelectrolytes…

4. Electrolytes? Pure water Tap water Sugar solution
Sodium chloride solution
Hydrochloric acid solution
Lactic acid solution
Ethyl alcohol solution
Pure sodium chloride

5. Answers to Electrolytes
NONELECTROLYTES:
Tap water (weak)
NaCl solution
HCl solution
Lactate solution (weak)
Pure water
Sugar solution
Ethanol solution
Pure NaCl
But why do some compounds conduct electricity in
solution while others do not…?
Answers to Electrolytes

6. Electrolytes Ionization Strong Weak
Formation of ions caused by a reaction between water molecules
Strong
Large amount of ionization occurs
Weak
Small amount of ionization occurs

7. Arrhenuis Definition
A substance that produces hydrogen ions (hydronium ions) as the only + ion when mixed with water
H+ = Hydrogen ion
H3O+ = Hydronium ion
The greater the # of H3O+ ions the stronger the acid and the stronger the electrolyte

8. Strong Acids vs. Weak Acids
Strong acids are assumed to be 100% ionized in solution (good proton donors).
HCl
H2SO4
HNO3
Weak acids are usually less than 5% ionized in solution (poor proton donors).
H3PO4
HC2H3O2
Organic acids

9. Strong Acid Ionization

10. Weak Acid Ionization

11. Organic Acids
Organic acids all contain the “carboxyl” group, sometimes several of them.
The carboxyl group is a poor proton donor, so ALL organic acids are weak acids.

12. Examples of Organic Acids
Citric acid in citrus fruit
Malic acid in sour apples
Deoxyribonucleic acid, DNA
Amino acids, the building blocks of protein
Lactic acid in sour milk and sore muscles
Butyric acid in rancid butter

13. Properties of Acids Acids taste sour Acids effect indicators
Blue litmus turns red
Methyl orange turns red
Acids have a pH lower than 7
Acids are proton (hydrogen ion, H+) donors
Acids react with active metals, produce H2
Acids neutralize bases

14. Acids you SHOULD know: Strong Acids Weak Acids Sulfuric acid, H2SO4
Phosphoric acid, H3PO4
Hydrochloric acid, HCl
Acetic acid, HC2H3O2
Nitric acid, HNO3

15. (image provided by NASA)
Sulfuric Acid
Highest volume production of any chemical in the U.S.
Used in the production of paper
Used in production of fertilizers
Used in petroleum refining
Thick clouds of sulfuric acid are a feature of the atmosphere of Venus.
(image provided by NASA)

16. Nitric Acid Used in the production of fertilizers
Used in the production of explosives
Nitric acid is a volatile acid – its reactive components evaporate easily
Stains proteins (including skin!)

17. Nitric Acid Used in the production of fertilizers
Used in the production of explosives
Nitric acid is a volatile acid – its reactive components evaporate easily
Stains proteins (including skin!)

18. Hydrochloric Acid Used in the pickling of steel
Used to purify magnesium from sea water
Part of gastric juice, it aids in the digestion of protein
Sold commercially as “Muriatic acid”

19. Phosphoric Acid A flavoring agent in sodas
Used in the manufacture of detergents
Used in the manufacture of fertilizers
Not a common laboratory reagent

20. Acetic Acid Used in the manufacture of plastics
Used in making pharmaceuticals
Acetic acid is the acid present in vinegar

21. Acids are Proton Donors
Monoprotic acids
Diprotic acids
Triprotic acids
H3PO4
HCl
H2SO4
HC2H3O2
H2CO3
HNO3

22. Acids Effect Indicators
Blue litmus paper turns red in contact with an acid.

23. Acids Have a pH less than 7

24. Acids React with Active Metals
Acids react with active metals to form salts and hydrogen gas.
Mg + 2HCl  MgCl2 + H2(g)
Zn + 2HCl  ZnCl2 + H2(g)
Mg + H2SO4  MgSO4 + H2(g)

25. Effects of Acid Rain on Marble (calcium carbonate)
George Washington:
BEFORE
George Washington:
AFTER

26. Arrhenuis Base
A base is any Hydroxide that dissolves in water to yield hydroxide ions as the only negative ion
NaOH
KOH
Mg(OH)2

27. Properties of Bases Bases effect indicators Red litmus turns blue
Bases taste bitter
Bases effect indicators
Red litmus turns blue
Phenolphthalein turns hot pink
Bases have a pH greater than 7
Bases are proton (hydrogen ion, H+) acceptors
Solutions of bases feel slippery
Bases neutralize acids

28. Examples of Bases Sodium hydroxide (lye), NaOH
Potassium hydroxide, KOH
Magnesium hydroxide, Mg(OH)2
Calcium hydroxide (lime), Ca(OH)2

29. Bases Effect Indicators
Red litmus paper turns blue in contact with a base.
Phenolphthalein turns purple in a base.

30. Bases have a pH greater than 7

31. Bases Neutralize Acids
Milk of Magnesia contains magnesium hydroxide, Mg(OH)2, which neutralizes stomach acid, HCl.
2 HCl + Mg(OH)2
MgCl2 + 2 H2O

32. Acids Neutralize Bases
Neutralization reactions ALWAYS produce a salt and water.
HCl + NaOH  NaCl + H2O
H2SO4 + 2NaOH  Na2SO4 + 2H2O
2HNO3 + Mg(OH)2  Mg(NO3)2 + 2H2O

33. Acid-Base Titration and pH

34. Self-Ionization of Water
H2O + H2O  H3O+ + OH-
Though pure water is considered a non-conductor, there is a slight, but measurable conductivity due to “self-ionization”

35. Ion Concentration in Solutions

36. pH Scale

37. Interpreting pH The term “pH” means power of hydrogen
Refers to the H+ ions released by the acids to form H3O+ ions
The more H+ released the more H3O+ and the lower the pH and stronger the acid
The lower the pH the greater the power of Hydrogen

38. pH The negative logarithm , to the base 10, of the H+ concentration
The log to the base 10 of a power 10 is equal to the power
-log [10-7] = 7

39. H+, OH-, and pH

40. Calculating pH, pOH Relationship between pH and pOH
pH = -log10(H3O+)
pOH = -log10(OH-)
Relationship between pH and pOH
pH + pOH = 14
Finding [H3O+], [OH-] from pH, pOH
[H3O+] = 10-pH
[OH-] = 10-pOH

41. Kw – Ionization Constant for Water
In pure water at 25 C:
[H3O+] = 1 x 10-7 mol/L
[OH-] = 1 x 10-7 mol/L
Kw is a constant at 25 C:
Kw = [H3O+][OH-]
Kw = (1 x 10-7)(1 x 10-7) = 1 x 10-14

42. Titrations
The molarity of an acid (or base) of unknown concentration can be determined by slowly combining it with a base(or acid) of known molarity(standard solution) until neutralization occurs
A method of determining the concentration of an acid or base by neutralizing it with a solution of known concentration
The end point is determined by the use of indicators. ( endpoint – when the right amount of standard solution has been added and neutralization as occurred)

43. Titration Moles = Volume x Molarity naVaMa = nbVbMb
na = # of H+ ions Ma = Molarity of acid
nb = # of OH- ions Mb = Molarity of base
Va = Volume of acid
Vb = Volume of base

44. pH Calculations

45. Measuring pH with wide-range paper

46. Narrow-Range pH Paper

47. Indicators
An indicator is a weak acid (or base) that changes its color in a known pH range when it gains or loses a H+ ion.
Phenolphthalein is a common indicator that is colorless when it is protonated (contains a H+) when it reacts with a base it loses it H+ and turns pink

48. Measuring pH Phenolphthalein changes from colorless to pink at pH 7–9.
Acid-base indicators respond to pH changes over a specific range. Phenolphthalein changes from colorless to pink at pH 7–9.

49. 19.2
Measuring pH
Indicators change color at a different pH. INTERPRETING GRAPHS a. Identify Which indicator changes color in a solution with a pH of 2? b. Compare and Contrast What do you notice about the range over which each indicator changes color? c. Apply Concepts Which indicator would you choose to show that a solution has changed from pH 3 to pH 5?

50. pH Indicators and their ranges

51. Measuring pH Acid-Base Indicators
19.2
Measuring pH Acid-Base Indicators
Universal Indicators
You can find acidic and basic substances in your home. a) Universal indicator solution has been added to solutions of known pH in the range from 1 to 12 to produce a set of reference colors. b) Universal indicator has been added to samples of vinegar, soda water, and ammonia solution. Interpreting Photographs Use the reference colors to assign pH values to vinegar, soda water, and ammonia solution.

52. Weak Acid/Strong Base Titration
Endpoint is above pH 7
A solution that is
0.10 M CH3COOH
is titrated with
0.10 M NaOH

53. Strong Acid/Strong Base Titration
Endpoint is at
pH 7
A solution that is
0.10 M HCl is titrated with
0.10 M NaOH

54. Strong Acid/Strong Base Titration
A solution that is
0.10 M NaOH is titrated with
0.10 M HCl
Endpoint is at
pH 7
It is important to recognize that titration curves are not always increasing from left to right.

55. Strong Acid/Weak Base Titration
A solution that is
0.10 M HCl is titrated with
0.10 M NH3
Endpoint is below
pH 7