1. Molecules, Compounds, and Chemical Equations
Chapter 3

2. Compounds may be ionic or molecular
IONIC COMPOUNDS
generally form between metals and nonmetals
held together by attraction of oppositely charged ions
MOLECULAR COMPOUNDS
generally form between nonmetals
held together by covalent chemical bonds

3. Elements & compounds

4. Most elements are atomic, but a few are molecular

5. Some compounds are ionic
An ionic compound (salt) is made of ions held together by electrostatic forces of attraction
Positively charged ions are called cations
Negatively charged ions are called anions
The basic unit of a salt is a formula unit
A formula unit is not a molecule, but the simplest ratio of cations & anions in the lattice

6. Sodium Chloride: an ionic compound

7. Some substances are molecular
A molecular substance (element or compound) is made of molecules (atoms joined by covalent bonds)
The basic unit of a molecular substance is a molecule

8. Molecular and ionic

9. Acetic acid contains 2 C, 2 O, and 4 H
Empirical formula CH2O
the simplest ratio of atoms
Molecular formula C2H4O2
the actual number of atoms
Structural formula
shows arrangement of atoms CH3–C–OH O ||

10. Mass Percent Composition
The mass of one element in a compound divided by the total mass of the compound, times 100%

11. Mass Percent Composition
Calculate the mass percent composition of acetic acid, HC2H3O2

12. Empirical Formula from Percent Composition
Use masses given, or assume you have 100 g of compound, so mass of each element = the percent given for each
Convert the mass of each element into moles
Write a tentative formula based on the moles calculated for each element
Divide all subscripts by the smallest value to convert them to small whole numbers

13. Calculating an Empirical Formula
Analysis of a sample of a brown gas which is an important air pollutant shows that it contains 2.34 g of nitrogen and 5.34 g of oxygen. What is the empirical formula of the gas?

14. Calculating an Empirical Formula
Analysis of a sample of a brown gas which is an important air pollutant shows that it is 30.47% nitrogen and 69.53% oxygen by mass. What is the empirical formula of the gas?
30.47 g N x 1 mol = mol N g
69.53 g O x 1 mol = mol O g
N2.175O N(2.175/2.175)O( ) N1.000O1.998
Empirical formula is NO2

15. Finding the Molecular Formula from the Empirical Formula
Molecular formula = actual number of atoms combined in the molecule
Find ratio true molar mass empirical molar mass
Multiply subscripts in empirical formula by ratio
empirical formula is CH & true molar mass is 78 g/mol
78 g/mol = 6
(12 + 1) g/mol
Molecular formula C6H6

16. Molecular Formulas
A compound has the empirical formula of NO2. Its molar mass is determined to be about 92 g/mol. What is the compound’s molecular formula?
The empirical formula mass is (16) = 46 g/mol
92 g/mol = g/mol
Molecular formula is N2O4

17. Empirical and Molecular Formulas Examples 3-5A and 3-5B
Diacetone glucose has a molecular mass of 260 amu and this composition: % C, 7.75% H, and 36.88% O. What are the empirical and molecular formulas of this substance?
Sorbitol has a molecular mass of 182 amu andthis composition: % C, 7.74% H, and 52.70% O. What are the empirical and molecular formulas of sorbitol?

18. Determining a Formula using Combustion Analysis

19. Tracking C and H atoms

21. Combustion Analysis
g of a C, H, and O compound is burned in O2 to yield g CO2 and g H2O
In a separate experiment, the molar mass is determined to be about 90 g/mol
Calculate
% composition
Empirical formula
Molecular formula

22. Combustion Analysis
g CO2 x 1 mol CO2 x 1 mol C g CO mol CO = mol C x g C = g C mol C
g H2O x 1 mol H2O x 2 mol H g H2O mol H2O = mol H x g H = g H mol H

23. Combustion Analysis
g of the compound contains g C g H g C + H
The rest of the compound is oxygen: g compound – g C+H = g O x 1 mol = mol O g

24. Combustion Analysis: % composition
g of the compound contains g C, g H, and g O
% C = g C x 100 = % C g
% H = g H x = % H g
% O = g O x = % O g
Total = % (just checking . . .)

25. Combustion Analysis: empirical formula
Compound contains mol C, mol H, and mol O
C H O
C( / )H(.01110/ )O( / )
C2.000H5.000O1.000
Empirical formula is C2H5O

26. Combustion Analysis: molecular formula
The empirical formula is C2H5O. The molar mass is approximately 90 g/mol
True molar mass = g/mol Empirical molar mass [2(12) + 5(1) + 16]
True molar mass = g/mol = 2 Empirical molar mass g/mol
Molecular formula is C4H10O2

27. Combustion Analysis Examples 3-6A and 3-6B
Isobutyl propionate is composed of carbon, hydrogen, and oxygen. Combustion of g of isobutyl propionate yields g CO2 and g H2O. What is its empirical formula ?
Thiophene is composed of carbon, hydrogen, and sulfur. Combustion of g thiophene yields g CO2, g H2O, and g SO2, which accounts for all of the sulfur. What is the empirical formula of thiophene?

28. Oxidation states
The oxidation state (O.S.) or oxidation number is a convenient but artificial way to describe the electron environment around an atom
It is related to the number of electrons gained, lost, or apparently used in forming compounds
Oxidation states are assigned using the rules on page 79 of your text (memorize these in order)

29. Assigning oxidation states
1. The O.S. of each atom in an element is zero.
2. The total of the O.S. of all atoms in any species (formula unit, molecule or ion) equals the charge on that species.
3. In compounds, Group 1A metals have O.S. +1 and Group 2A metals have O.S. +2.
4. In compounds, the O.S. of fluorine is –1.
5. In compounds, the O.S. of hydrogen is +1.
6. In compounds, the O.S. of oxygen is –2.
7. In binary compounds with metals, the O.S. of a Group 7A element is –1, Group 6A element –2, and Group 5A element –3.

30. Assigning oxidation states Examples 3-7A and 3-7B
What is the oxidation state of the underlined element in
S Cr2O72– Cl2O KO2
–1/2
S2O32– Hg2Cl KMnO H2CO

31. Nomenclature: Binary Ionic Compounds
Binary ionic compounds: metal + nonmetal
Nomenclature of binary ionic compounds
Write name of metal cation (same as element name)
Write name of nonmetal anion, with element name modified to end in “–ide”
No prefixes to indicate number of ions
Roman numeral shows O.S. of transition metal cation
Compound is electrically neutral, so in formula total cation charge = total anion charge

32. Binary ionic compounds Examples 3-8A and 3-8B
Write the formulas for the compounds
Lithium oxide
Tin (II) fluoride
Lithium nitride
Aluminum sulfide
Magnesium nitride
Vanadium (III) oxide

33. Binary ionic compounds Examples 3-8A and 3-8B
Write the formulas for the compounds
Lithium oxide Li2O
Tin (II) fluoride SnF2
Lithium nitride Li3N
Aluminum sulfide Al2S3
Magnesium nitride Mg3N2
Vanadium (III) oxide V2O3

34. Binary ionic compounds Examples 3-9A and 3-9B
Write acceptable names for the compounds
CsI CaF2 FeO CrCl3
CaH2 CuCl Ag2S Hg2Cl2

35. Binary ionic compounds Examples 3-9A and 3-9B
Write acceptable names for the compounds
CsI CaF2 FeO CrCl3
cesium iodide iron (II) oxide
calcium fluoride chromium (III) chloride
CaH2 CuCl Ag2S Hg2Cl2
calcium hydride silver (I) sulfide
copper (I) chloride mecury (I) chloride

36. Nomenclature: Binary Molecular Compounds
Binary molecular compounds: nonmetal+nonmetal
Nomenclature of binary molecular compounds
Write name of element with positive O.S. first
Write name of element with negative O.S. second, with element name modified to end in “–ide”
Use prefixes to indicate number of atoms of each element

37. Binary Molecular Compounds Examples
Write the formulas for the compounds
Carbon tetrabromide
Dinitrogen pentoxide
Phosphorus triiodide
Write acceptable names for the compounds
SF6 Cl2O7 IBr3

38. Binary Molecular Compounds Examples
Write the formulas for the compounds
Carbon tetrabromide CBr4
Dinitrogen pentoxide N2O5
Phosphorus triiodide PI3
Write acceptable names for the compounds
SF6 Cl2O7 IBr3
sulfur hexafluoride
dichlorine heptoxide
iodine tribromide
Watch your
spelling!

39. Nomenclature: Binary acids
Binary acids: certain compounds of H + nonmetal
Produce hydrogen ions (H1+) when dissolved in water
Name as acid when focus is on behavior in water
Write prefix “hydro” for hydrogen
Write nonmetal element, with name modified to end in “–ic,” then write acid
Formula must be electrically neutral

40. Binary acids Examples Write the formulas for the compounds
Hydrochloric acid
Hydroiodic acid
Hydrosulfuric acid
Write acceptable names for the compounds
HBr H2S HF

41. Binary acids Examples Write the formulas for the compounds
Hydrochloric acid HCl
Hydroiodic acid HI
Hydrosulfuric acid H2S
Write acceptable names for the compounds
HBr H2S HF
hydrobromic acid
hydrosulfuric acid
hydrofuoric acid

42. Nomenclature: Polyatomic Ions
Polyatomic ions are ions consisting of two or more covalently bound atoms that carry a charge
Most are anions (exception: ammonium, NH41+)
Very few polyatomic anion names end in “–ide”
Cyanide, CN1– Hydroxide, OH1–
Most names end in “–ate” or “–ite”

43. Nomenclature: Oxoanions
Polyatomic ions that contain oxygen are oxoanions
A nonmetal may form several oxoanions with different numbers of oxygens
As nonmetal O.S. increases (number of oxygens increases), name changes sysematically:
ClO1– ClO21– ClO31– ClO41– hypochlorite chlorite chlorate perchlorate
SO32– SO42– sulfite sulfate
All common oxoanions of halogens are –1

44. Nomenclature: Oxoanions
Polyatomic ions that contain oxygen are oxoanions
Some oxoanions include varying numbers of hydrogens
PO43– HPO42– H2PO41– phosphate hydrogen phosphate dihydrogen phosphate
O.S. of central nonmetal is constant: ion charge changes as number of hydrogens varies
Prefix “thio–” indicates an S has substituted for an O
SO42– S2O32– sulfate thiosulfate

45. Nomenclature: Oxoacids
Oxoacids are combinations of hydrogen ions (H1+) and oxoanions
H1+ + oxoanion = acid, a molecular compound
Metal ion + oxoanion = salt, an ionic compound
Oxoacid name derived from oxoanion name
Change “–ite” to “–ous” and “–ate” to “–ic”
Add “acid” to end of name
Formulas are electrically neutral

46. Nomenclature: Oxoacids Examples
Write acceptable names for the compounds
H2SO3 HNO3 HClO
Write the formulas for the compounds
Phosphoric acid
Nitrous acid
Perchloric acid

47. Nomenclature: Oxoacids Examples
Write acceptable names for the compounds
H2SO HNO3 HClO
sulfurous acid nitric acid hypochlorous acid
Write the formulas for the compounds
Phosphoric acid H3PO4
Nitrous acid HNO2
Perchloric acid HClO4

48. Nomenclature Examples 3-10A and 3-10B
Name the compounds
SF HNO Ca(HCO3) FeSO4
NH4NO PCl HBrO AgClO Fe2(SO4)3

49. Nomenclature Examples 3-10A and 3-10B
Name the compounds
SF HNO Ca(HCO3) FeSO4
Sulfur hexafluoride Calcium hydrogen carbonate
Nitrous acid Iron (II) sulfate
NH4NO PCl HBrO AgClO Fe2(SO4)3
Ammonium nitrate
Phosphorus trichloride
Hypobromous acid
Ailver perchlorate
Iron (III) sulfate

50. Nomenclature Examples3-11A and 3-11B
Write formulas for the compounds
Boron trifluoride
Potassium dichromate
Sulfuric acid
Calcium chloride
Aluminum nitrate
Tetraphosphorous decoxide
Chromium (III) hydroxide
Iodic acid

51. Nomenclature Examples3-11A and 3-11B
Write formulas for the compounds
Boron trifluoride BF3
Potassium dichromate K2Cr2O7
Sulfuric acid H2SO4
Calcium chloride CaCl2
Aluminum nitrate Al(NO3)3
Tetraphosphorous decoxide P4O10
Chromium (III) hydroxide Cr(OH)3
Iodic acid HIO3

52. Slaying the nomenclature dragon
Make flash cards of all the ion names, formulas and charges and all the acid names and formulas (Tables 3.1, 3.3, and 3.4 in Chapter 3), and of the Greek prefixes (mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca)
Concentrate on writing formulas from names (that’s what’s on the AP exam)
For ionic formulas and acid, be sure charges balance!

53. Exercise 32
The hemoglobin content of blood is about 15.5 g/100 mL blood. The molar mass of hemoglobin is about 64,500 g/mol, and there are 4 Fe atoms in a hemoglobin molecule. Approximately how many Fe atoms are present in the 6 L of blood in a typical adult?

54. Exercise 38
Determine the mass percent of each element in the antimalarial drug quinine, C20H24N2O2

55. Exercise 45 Determin the empirical formula of
Warfarin, 74.01% C, 5.23% H, and 20.76% O by mass
Mustard gas, 30.20% C, 5.07% H, 44.58% Cl, and 20.16% S by mass

56. Exercise 47
Indigo has the mass composition 73.27% C, 3.84% H, 10.68% N, and the remainder oxygen. Its molecular mass is amu. What is the molecular formula of indigo?

57. Exercise 50
The element X forms the chloride XCl4 containing 75.0% Cl, by mass. What is the identity of element X?

58. Exercise 51
A g sample of a hydrocarbon produces g CO2 and g H2O in combustion analysis. Its molecular mass is found to be 106 amu. Determine the mass composition, empirical formula, and molecular formula of this hydrocarbon.

59. Exercises 57 and 60
Indicate the oxidations state of the underlined element:
CH SF Na2O C2H3O21– FeO42–
Nitrogen forms five oxides. Write appropriate formulas for these compounds if the O.S. of N in them are +1, +2, +3, +4, and +5, respectively.

60. Exercise 62 Name these compounds Ba(NO3)2 HNO2 CrO2 KIO3
LiCN KIO Fe(OH) Ca(H2PO4)2
H3PO NaHSO Na2Cr2O NH4C2H3O2
MgC2O Na2C2O4

61. Exercise 64 Assign suitable names to these compounds
ICl ClF SF BrF N2O S4N4

62. Exercise 66 Write correct formulas for Magnesium perchlorate
Lead (II) acetate
Tin (IV) oxide
Hydroiodic acid
Chlorous acid
Sodium hydrogen sulfite
Calcium dihydrogen phosphate
Aluminum phosphate
Dinitrogen tetroxide
Disulfur dichloride

63. Exercise 77
A sample of MgSO4•xH2O weighing g is heated until all the water of hydration is driven off. The resulting anhydrous compound, MgSO4, weighs g. What is the formula of the hydrate?

64. Types of Compounds
NaCl, salt
Buckyball, C60
Methane, CH4

65. PREDICTING ION CHARGES
metals lose electrons cations
nonmetals gain electrons  anions

66. MAIN GROUP METALS M  n e- + Mn+
where n = group number on periodic table
Group 1 Na  1 e Na1+
Group 2 Mg  2 e Mg2+
Group 3 Al  3 e Al3+

67. TRANSITION METALS Zn  2 e- + Zn2+ Ag  1 e- + Ag1+
Other transition metal ion charges not easily predicted from periodic table
M2+ or M3+ are common

68. NONMETALS X + n e-  Xn- where n = 8 – group number
Group 5 N + (8–5) e-  N3-
Group 6 O + (8–6) e-  O2-
Group 7 F + (8–7) e-  F1-

69. Symbols and Locations of
Monatomic Ions
Sc3+
Cd2+

70. Molecular Compounds
A molecule is a group of bonded atoms that exists as a distinct entity
The atoms in a molecule are held together by covalent bonds
Molecular compounds consist of discrete molecules

71. Water: a molecular compound

72. Acetic acid: a molecular compound

73. Molar Mass The mass of one mole of any element or compound
H2O 2 H x = O x =
Molar mass of H2O = g/mol

74. SOME MOLECULAR ELEMENTS

75. Molar mass and mole concept Examples 3-1A and 3-1B
What is the total number of ions present in a 1.0 g sample of zinc oxide, ZnO?
How many grams of MgCl2 are needed to provide 5.0 x 1023 Cl1- ions?

76. Molar mass and mole concept Examples 3-2A and 3-2B
Gold has a density of g/cm3. How many atoms of gold are in a piece of gold leaf that is 2.50 cm on each side and mm thick?
If 1.0 mL of liquid ethyl mercaptan, C2H6S (d = 0.84 g/mL) is allowed to evaporate and distribute itself throughout a 1500 m3 room,will the vapor be detectable in the room? The limit of detectability is 9 x 10-4 mmol/m3.

77. Molar mass and mole concept Examples 3-3A and 3-3B
How many grams of C are contained in 75.0 mL of halothane, C2HBrClF3 (d = g/mL)?
How many mL of halothane, C2HBrClF3 (d = g/mL), contain g Br?