1. Chemists Have Solutions I
Solution Chemistry

2. Chemists Have Solutions
Solution Concentrations (Molarity, Molality, Percent)
Acids and Bases
Theories
Arrhenius, Brønsted-Lowry, Lewis
Strong and Weak Acids and Bases
The pH scale
Neutralization Reactions: Concepts and Problems
Applications in Industry, Household, Health
Basic Reduction and Oxidation
Definitions: Oxidation, Reduction, Reducing Agent, Oxidizing Agent
Redox Reactions
Applications and Examples: Batteries, Corrosion, Common oxidizing and reducing agents

3. A solution is a homogenous mixture of 2 or more substances
The solute is(are) the substance(s) present in the smaller amount(s)
The solvent is the substance present in the larger amount
Solution
Solvent
Solute
Soft drink (l)
Air (g)
Soft Solder (s) Pb Sn
4.1

4. An electrolyte is a substance that, when dissolved in water, results in a solution that can conduct electricity.
A nonelectrolyte is a substance that, when dissolved, results in a solution that does not conduct electricity.
nonelectrolyte
weak electrolyte
strong electrolyte
4.1

5. Conduct electricity in solution?
Cations (+) and Anions (-)
Strong Electrolyte – 100% dissociation
NaCl (s) Na+ (aq) + Cl- (aq)
H2O
Weak Electrolyte – not completely dissociated
CH3COOH CH3COO- (aq) + H+ (aq)
4.1

6. Ionization of acetic acid
CH3COOH CH3COO- (aq) + H+ (aq)
A reversible reaction. The reaction can occur in both directions.
Acetic acid is a weak electrolyte because its ionization in water is incomplete.
4.1

7. Hydration is the process in which an ion is surrounded by water molecules arranged in a specific manner. d+ d-
H2O
4.1

8. Nonelectrolyte does not conduct electricity?
No cations (+) and anions (-) in solution
C6H12O6 (s) C6H12O6 (aq)
H2O
4.1

9. Recall: Precipitation Reactions
Precipitate – insoluble solid that separates from solution
precipitate
Pb(NO3)2 (aq) + 2KI (aq) PbI2 (s) + 2KNO3 (aq)
molecular equation
4.2

10. Chemistry In Action: Stalactite Formation
Water + carbon dioxide carbonic acid (dissolves CaCO3)
Calcium bicarbonate to calcium carbonate, water, CO3
4.2

11. Solution Stoichiometry
The concentration of a solution is the amount of solute present in a given quantity of solvent or solution.
M = molarity =
moles of solute
liters of solution
What mass of KI is required to make 500. mL of
a 2.80 M KI solution?
volume KI
moles KI
grams KI
4.5

12. Molarity: Moles of solute per liter of solution.
Solution Composition
Molarity (M)
Molarity: Moles of solute per liter of solution.

13. Test Yourself
How many moles of potassium bromide are in 200.0mL of a 1.5M solution?
What is the concentration, in M, of 20.00g Lead (II) Nitrate in 50.0L of solution?
What is the concentration, in M, of 30.0g glucose (C6H12O6), in mL of water? Assume no volume changes.
How much salt must I dissolve in 2.00L water to make a 5.0M solution? Assume no volume changes.
What will be the mass of table salt I can recover from the complete drying of 50.00mL 0.50M salt solution?

14. Molality: Moles of solute per kilogram solvent.
Solution Composition
MOLALITY (m)
Molality: Moles of solute per kilogram solvent.

15. Percent Concentration (pph)
Also pph: part per hundred
% Conc. (v/v) = vol. solute x 100%
vol. sol’n.
% Conc. (w/v) = mass. Solute (g) x 100%
vol. sol’n. (mL)
What is the % concentration of 20.0mL pure ethanol diluted to 100.0mL?
What is the molarity of 50% (w/v) NaOH?

16. Dilution is the procedure for preparing a less concentrated solution from a more concentrated solution.
Dilution
Add Solvent
Moles of solute
before dilution (i)
after dilution (f) =
MiVi
MfVf =
4.5

17. How would you prepare 60.0 mL of 0.2 M
HNO3 from a stock solution of 4.00 M HNO3?
MiVi = MfVf
4.5

18. Test Yourself
I have 20.0L of 1.00M HCl. If I need 0.500M HCl, to what final volume must I add water to the HCl I have?
I need to make 200.0mL of 0.350M NaOH. I have an unlimited supply of water and stock 0.50M NaOH. What must I do?

19. Test Yourself: Solution Stoichiometry
Lead (II) nitrate and potassium iodide react in a methathesis reaction to form insoluble lead (II) iodide and aqueous potassium nitrate. If I combine 10.0mL of M lead (II) nitrate with 5.00mL of M potassium iodide, what will be the mass of lead iodide produced?
I produced 1.00g of lead (II) iodide in the reaction above by combining 10.0mL of lead (II) nitrate with an excess of potassium iodide. What was the concentration of lead (II) nitrate solution?

20. Chemists Have Solutions II
Acids and Bases

21. Acids Have a sour taste. Vinegar owes its taste to acetic acid. Citrus
fruits contain citric acid.
Cause color changes in plant dyes.
React with certain metals to produce hydrogen gas.
2HCl (aq) + Mg (s) MgCl2 (aq) + H2 (g)
React with carbonates and bicarbonates to produce carbon
dioxide gas
2HCl (aq) + CaCO3 (s) CaCl2 (aq) + CO2 (g) + H2O (l)
Aqueous acid solutions conduct electricity.
4.3

22. Bases Have a bitter taste. Feel slippery. Many soaps contain bases.
Cause color changes in plant dyes.
Aqueous base solutions conduct electricity.
4.3

23. Arrhenius acid is a substance that produces H+ (H3O+) in water
Arrhenius base is a substance that produces OH- in water
4.3

24. A Brønsted acid is a proton donor A Brønsted base is a proton acceptor
A Brønsted acid must contain at least one
ionizable proton!
4.3

25. Monoprotic acids Diprotic acids Triprotic acids HCl H+ + Cl-
Strong electrolyte, strong acid
HNO H+ + NO3-
Strong electrolyte, strong acid
CH3COOH H+ + CH3COO-
Weak electrolyte, weak acid
Diprotic acids
H2SO H+ + HSO4-
Strong electrolyte, strong acid
HSO H+ + SO42-
Weak electrolyte, weak acid
Triprotic acids
H3PO H+ + H2PO4-
Weak electrolyte, weak acid
H2PO H+ + HPO42-
Weak electrolyte, weak acid
HPO H+ + PO43-
Weak electrolyte, weak acid
4.3

26. HI (aq) H+ (aq) + Br- (aq) Brønsted acid
Identify each of the following species as a Brønsted acid, base, or both. (a) HI, (b) CH3COO-, (c) H2PO4-
HI (aq) H+ (aq) + Br- (aq)
Brønsted acid
CH3COO- (aq) + H+ (aq) CH3COOH (aq)
Brønsted base
H2PO4- (aq) H+ (aq) + HPO42- (aq)
Brønsted acid
H2PO4- (aq) + H+ (aq) H3PO4 (aq)
Brønsted base
4.3

27. [ ] - Acid-Base Properties of Water autoionization of water
H2O (l) H+ (aq) + OH- (aq)
autoionization of water O H + - [ ]
conjugate acid
base
H2O + H2O H3O+ + OH-
conjugate base
acid
15.2

28. Hydronium ion, hydrated proton, H3O+
4.3

29. The Ion Product of Water
Kc =
[H+][OH-]
[H2O]
H2O (l) H+ (aq) + OH- (aq)
[H2O] = constant
Kc[H2O] = Kw = [H+][OH-]
The ion-product constant (Kw) is the product of the molar concentrations of H+ and OH- ions at a particular temperature.
Solution Is
[H+] = [OH-]
neutral
At 250C
Kw = [H+][OH-] = 1.0 x 10-14
[H+] > [OH-]
acidic
[H+] < [OH-]
basic
15.2

30. What is the concentration of OH- ions in a HCl solution whose hydrogen ion concentration is 1.3 M?
Kw = [H+][OH-] = 1.0 x 10-14
[H+] = 1.3 M
[OH-] = Kw
[H+]
1 x 10-14
1.3 =
= 7.7 x M
15.2

31. pH – A Measure of Acidity
pH = -log [H+]
Solution Is
At 250C
neutral
[H+] = [OH-]
[H+] = 1 x 10-7
pH = 7
acidic
[H+] > [OH-]
[H+] > 1 x 10-7
pH < 7
basic
[H+] < [OH-]
[H+] < 1 x 10-7
pH > 7 pH
[H+]
15.3

32. pOH = -log [OH-] [H+][OH-] = Kw = 1.0 x 10-14
-log [H+] – log [OH-] = 14.00
pH + pOH = 14.00
15.3

33. The pH Scale

34. The pH Scale
Measuring pH

35. The pH of rainwater collected in a certain region of the northeastern United States on a particular day was What is the H+ ion concentration of the rainwater?
pH = -log [H+]
[H+] = 10-pH =
= 1.5 x 10-5 M
NOTE that pH 4.82 only has TWO significant figures. Thus, our final answer also has TWO significant figures
The OH- ion concentration of a blood sample is 2.5 x 10-7 M. What is the pH of the blood?
pH + pOH = 14.00
pOH = -log [OH-]
= -log (2.5 x 10-7)
= 6.60
pH = – pOH = – 6.60 = 7.40
NOTE that 2.5 x 10-7M has TWO significant figures. The answers in pH and pOH, therefore, must also have two sig.figs. BUT, we only start counting sig.figs AFTER the decimal point for pH and pOH (as well as other “p” values).
15.3

36. Strong Electrolyte – 100% dissociation
NaCl (s) Na+ (aq) + Cl- (aq)
H2O
Weak Electrolyte – not completely dissociated
CH3COOH CH3COO- (aq) + H+ (aq)
Strong Acids are strong electrolytes
HCl (aq) + H2O (l) H3O+ (aq) + Cl- (aq)
HNO3 (aq) + H2O (l) H3O+ (aq) + NO3- (aq)
HClO4 (aq) + H2O (l) H3O+ (aq) + ClO4- (aq)
H2SO4 (aq) + H2O (l) H3O+ (aq) + HSO4- (aq)
15.4

37. Weak Acids are weak electrolytes
HF (aq) + H2O (l) H3O+ (aq) + F- (aq)
HNO2 (aq) + H2O (l) H3O+ (aq) + NO2- (aq)
HSO4- (aq) + H2O (l) H3O+ (aq) + SO42- (aq)
H2O (l) + H2O (l) H3O+ (aq) + OH- (aq)
Strong Bases are strong electrolytes
NaOH (s) Na+ (aq) + OH- (aq)
H2O
KOH (s) K+ (aq) + OH- (aq)
H2O
Ba(OH)2 (s) Ba2+ (aq) + 2OH- (aq)
H2O
15.4

38. Weak Bases are weak electrolytes
F- (aq) + H2O (l) OH- (aq) + HF (aq)
NO2- (aq) + H2O (l) OH- (aq) + HNO2 (aq)
Conjugate acid-base pairs:
The conjugate base of a strong acid has no measurable strength.
H3O+ is the strongest acid that can exist in aqueous solution.
The OH- ion is the strongest base that can exist in aqeous solution.
15.4

39. 15.4

40. Strong Acid
Weak Acid
15.4

41. What is the pH of a 2 x 10-3 M HNO3 solution?
HNO3 is a strong acid – 100% dissociation.
Start
0.002 M
0.0 M
0.0 M
HNO3 (aq) + H2O (l) H3O+ (aq) + NO3- (aq)
End
0.0 M
0.002 M
0.002 M
pH = -log [H+] = -log [H3O+] = -log(0.002) = 2.7
What is the pH of a 1.8 x 10-2 M Ba(OH)2 solution?
Ba(OH)2 is a strong base – 100% dissociation.
Start
0.018 M
0.0 M
0.0 M
Ba(OH)2 (s) Ba2+ (aq) + 2OH- (aq)
End
0.0 M
0.018 M
0.036 M
pH = – pOH = log(0.036) = 12.56
15.4

42. Definition of An Acid
Arrhenius acid is a substance that produces H+ (H3O+) in water
A Brønsted acid is a proton donor
A Lewis acid is a substance that can accept a pair of electrons
A Lewis base is a substance that can donate a pair of electrons
+ OH- •
H O H • H+
acid
base
N H • H
N H H + H+ +
acid
base
15.12

43. No protons donated or accepted!
Lewis Acids and Bases
F B F
N H • H
F B F
N H H +
acid
base
No protons donated or accepted!
15.12

44. Chemistry In Action: Antacids and the Stomach pH Balance
NaHCO3 (aq) + HCl (aq)
NaCl (aq) + H2O (l) + CO2 (g)
Mg(OH)2 (s) + 2HCl (aq)
MgCl2 (aq) + 2H2O (l)

45. Neutralization Reaction
acid + base salt + water
HCl (aq) + NaOH (aq) NaCl (aq) + H2O
H+ + Cl- + Na+ + OH Na+ + Cl- + H2O
H+ + OH H2O
4.3

46. Sample Problem
Sodium hydroxide reacts with HCl in a neutralization reaction. If I mix 30mL of M NaOH and 50mL of M HCl, how many moles of NaCl will be produced?
Follow-up question: What will be the final concentration of this salt? (Take note of the final volume of the combined solution.)

47. Test yourself What will be the pH of a 0.000211M HCl solution?
I dissolved 1.00g of NaOH in 1.000L solution. What will be the final pH?
What volume of M NaOH is needed to completely neutralize 20.00mL of M HCl? If I evaporate the end product, what mass of salt will I obtain?
I combined 10.00mL M NaOH with 30.00mL M HCl. What will be the final pH of the final solution created? (TIP: The final pH will be based on any unreacted H+ or OH-. Assume all volumes are simply additive.)

48. Chemists Have Solutions III
Redox Reactions

49. Oxidation-Reduction Reactions
(electron transfer reactions)
2Mg (s) + O2 (g) MgO (s)
2Mg Mg2+ + 4e-
Oxidation half-reaction (lose e-)
O2 + 4e O2-
Reduction half-reaction (gain e-)
2Mg + O2 + 4e Mg2+ + 2O2- + 4e-
2Mg + O MgO
Magnesium lost electrons. Thus, Mg is is oxidized. It is the reducing agent.
O2 gained electrons. Thus, O2 is reduced. It is the oxidizing agent.
4.4

50. Some Mnemonics OIL RIG LEO GER What is Oxidized is the reducing agent
Oxidation Is Loss of electrons, Reduction Is Gain of electrons
LEO GER
Loss of Electrons is Oxidation. Gain of Electrons is Reduction
What is Oxidized is the reducing agent
What is Reduced is the oxidizing agent

51. The earlier definition involved electrons
The earlier definition involved electrons. Looking at simple reactions, we also find some trends. Usually:
If a substance GAINS OXYGEN atoms, there is OXIDATION (naturally)
If a substance GAINS HYDROGEN atoms, there is REDUCTION

52. 4.4

53. Zn (s) + CuSO4 (aq) ZnSO4 (aq) + Cu (s)
Zn Zn2+ + 2e-
Zn is oxidized
Zn is the reducing agent
Cu2+ + 2e Cu
Cu2+ is reduced
Cu2+ is the oxidizing agent
Copper wire reacts with silver nitrate to form silver metal.
What is the oxidizing agent in the reaction?
Cu (s) + 2AgNO3 (aq) Cu(NO3)2 (aq) + 2Ag (s)
Cu Cu2+ + 2e-
Ag+ + 1e Ag
Ag+ is reduced
Ag+ is the oxidizing agent
4.4

54. Li+, Li = +1; Fe3+, Fe = +3; O2-, O = -2
Oxidation number
The charge the atom would have in a molecule (or an
ionic compound) if electrons were completely transferred.
Free elements (uncombined state) have an oxidation number of zero.
Na, Be, K, Pb, H2, O2, P4 = 0
In monatomic ions, the oxidation number is equal to the charge on the ion.
Li+, Li = +1; Fe3+, Fe = +3; O2-, O = -2
The oxidation number of oxygen is usually –2. In H2O2 and O22- it is –1.
4.4

55. HCO3- O = -2 H = +1 3x(-2) + 1 + ? = -1 C = +4
The oxidation number of hydrogen is +1 except when it is bonded to metals in binary compounds. In these cases, its oxidation number is –1.
Group IA metals are +1, IIA metals are +2 and fluorine is always –1.
6. The sum of the oxidation numbers of all the atoms in a molecule or ion is equal to the charge on the molecule or ion.
HCO3-
Oxidation numbers of all the elements in HCO3- ?
O = -2
H = +1
3x(-2) ? = -1
C = +4
4.4

56. Figure 4.10 The oxidation numbers of elements in their compounds
4.4

57. IF7 F = -1 7x(-1) + ? = 0 I = +7 K2Cr2O7 NaIO3 Na = +1 O = -2 O = -2
Oxidation numbers of all the elements in the following ?
F = -1
7x(-1) + ? = 0
I = +7
K2Cr2O7
NaIO3
Na = +1
O = -2
O = -2
K = +1
3x(-2) ? = 0
7x(-2) + 2x(+1) + 2x(?) = 0
I = +5
Cr = +6
4.4

58. Types of Oxidation-Reduction Reactions
Combination Reaction
A + B C +4 -2
S + O SO2
Decomposition Reaction
C A + B +1 +5 -2 +1 -1
2KClO KCl + 3O2
4.4

59. Types of Oxidation-Reduction Reactions
Displacement Reaction (Examples here are all single displacement rxns)
A + BC AC + B +1 +2
Sr + 2H2O Sr(OH)2 + H2
Hydrogen Displacement +4 +2
TiCl4 + 2Mg Ti + 2MgCl2
Metal Displacement -1 -1
Cl2 + 2KBr KCl + Br2
Halogen Displacement
4.4

60. The Activity Series for Metals
Hydrogen Displacement Reaction
M + BC AC + B
M is metal
BC is acid or H2O
B is H2
Ca + 2H2O Ca(OH)2 + H2
Pb + 2H2O Pb(OH)2 + H2
Figure 4.15
4.4

61. Types of Oxidation-Reduction Reactions
Disproportionation Reaction
Element is simultaneously oxidized and reduced. +1 -1
Cl2 + 2OH ClO- + Cl- + H2O
Chlorine Chemistry
4.4

62. Chemistry in Action: Breath Analyzer+6
3CH3CH2OH + 2K2Cr2O7 + 8H2SO4 +3
3CH3COOH + 2Cr2(SO4)3 + 2K2SO4 + 11H2O
4.4