1. More on Chemical Compounds Nomenclature
Chapter #6
More on Chemical Compounds
Nomenclature

2. Ions Atoms can form ions by gaining or losing electrons.
Metals tend to lose one or more electrons, to become isoelectronic with Noble gasses, to form positive ions called cations and are named by using the name of the parent atom.
Nonmetals tend to gain electrons, to become isoelectronic with Noble gasses, to form negative ions called anions and are named by using the root of the atom name followed by the suffix –ide.
Atoms become more stable by gaining or losing
electrons.

3. Common Oxidation States

4. Common Oxidation States1+ 2+ 3- 2- 1- 3+ 4+

5. Common Oxidation States
By Group Number

6. Sample Problem
An ion with a 3+ charge contains 23 electrons. Which ion is it?

7. Sample Problem
An ion with a 3+ charge contains 23 electrons. Which ion is it? Fe3+
A certain ion X+ contains 54 electrons and 78 neutrons. What is the mass number of this ion?

8. Sample Problem
An ion with a 3+ charge contains 23 electrons. Which ion is it? Fe3+
A certain ion X+ contains 54 electrons and 78 neutrons. What is the mass number of this ion?

9. Sample Problem
An ion with a 3+ charge contains 23 electrons. Which ion is it? Fe3+
A certain ion X+ contains 54 electrons and 78 neutrons. What is the mass number of this ion?
133

10. Ionic Compounds Ions combine to form ionic compounds.
The simplest ratio between the ions is called the empirical formula or a formula unit.
Properties of ionic compounds
High melting points
Conduct electricity
If melted
If dissolved in water
Ionic compounds are electrically neutral.
The charges on the anions and cations in the compound must sum to zero.

11. Ionic Compounds Crystal Lattice of NaCl
Ionic compounds do not exist as discrete molecules. Instead they exist as crystals where ions of opposite charges occupy positions known as lattice sites.
Ions combine in the ratio that results in zero charge to form ionic compounds.
Which ions are the smaller ones?
Crystal Lattice of NaCl

12. Formula Writing Rules Examples
Step 1 Write the symbols of the elements.
Step 2 Assign oxidation numbers (O.N. = P – e)
Step 3 Slide with Clyde! (number only)
Step 4 Reduce if the compound is ionic
Examples
Write formulas for the following two elements
Sodium and oxygen
Sodium and nitrogen
Calcium and oxygen
Calcium and phosphorus

13. Formula Writing Rules Examples Na O Na N Ca O Ca P
Step 1 Write the symbols of the elements.
Step 2 Assign oxidation numbers O.N. = (P – e)
Step 3 Slide with Clyde! (number only)
Step 4 Reduce if the compound is ionic
Examples
Write formulas for the following two elements 1+
Sodium and oxygen
Sodium and nitrogen
Calcium and oxygen
Calcium and phosphorus 2- Na O Na N Ca O Ca P

14. Formula Writing Rules Examples Na O Na N Ca O Ca P
Step 1 Write the symbols of the elements.
Step 2 Assign oxidation numbers O.N. = (P – e)
Step 3 Slide with Clyde! (number only)
Step 4 Reduce if the compound is ionic
Examples
Write formulas for the following two elements 1+
Sodium and oxygen
Sodium and nitrogen
Calcium and oxygen
Calcium and phosphorus 2- Na O 1+ 3- Na N Ca O Ca P

15. Formula Writing Rules Examples Na O Na N Ca O Ca P
Step 1 Write the symbols of the elements.
Step 2 Assign oxidation numbers O.N. = (P – e)
Step 3 Slide with Clyde! (number only)
Step 4 Reduce if the compound is ionic
Examples
Write formulas for the following two elements 1+
Sodium and oxygen
Sodium and nitrogen
Calcium and oxygen
Calcium and phosphorus 2- Na O 1+ 3- Na N 2+ 2- Ca O Ca P

16. Formula Writing Rules Examples Na O Na N Ca O Ca P
Step 1 Write the symbols of the elements.
Step 2 Assign oxidation numbers O.N. = (P – e)
Step 3 Slide with Clyde! (number only)
Step 4 Reduce if the compound is ionic
Examples
Write formulas for the following two elements 1+
Sodium and oxygen
Sodium and nitrogen
Calcium and oxygen
Calcium and phosphorus 2- Na O 1+ 3- Na N 2+ 2- Ca O 2+ Ca P 3-

17. Formula Writing Rules Examples Na O Na N Ca O Ca P
Step 1 Write the symbols of the elements.
Step 2 Assign oxidation numbers O.N. = (P – e)
Step 3 Slide with Clyde! (number only)
Step 4 Reduce if the compound is ionic
Examples
Write formulas for the following two elements 1+
Sodium and oxygen
Sodium and nitrogen
Calcium and oxygen
Calcium and phosphorus 2- Na O 1+ 3- Na N 2+ 2- Ca O 2+ Ca P 3-

18. Formula Writing Rules Examples Na O Na O Na N Ca O Ca P
Step 1 Write the symbols of the elements.
Step 2 Assign oxidation numbers O.N. = (P – e)
Step 3 Slide with Clyde! (number only)
Step 4 Reduce if the compound is ionic
Examples
Write formulas for the following two elements 1+
Sodium and oxygen
Sodium and nitrogen
Calcium and oxygen
Calcium and phosphorus 2- Na O Na O ≡ 2 1+ 3- Na N 2+ 2- Ca O 2+ Ca P 3-

19. Formula Writing Rules Examples Na O Na O Na N Na N Ca O Ca P
Step 1 Write the symbols of the elements.
Step 2 Assign oxidation numbers O.N. = (P – e)
Step 3 Slide with Clyde! (number only)
Step 4 Reduce if the compound is ionic
Examples
Write formulas for the following two elements 1+
Sodium and oxygen
Sodium and nitrogen
Calcium and oxygen
Calcium and phosphorus 2- Na O Na O ≡ 2 1+ 3- Na N Na N ≡ 3 2+ 2- Ca O 2+ Ca P 3-

20. Formula Writing Rules Examples Na O Na O Na N Na N Ca O Ca O Ca O Ca P
Step 1 Write the symbols of the elements.
Step 2 Assign oxidation numbers O.N. = (P – e)
Step 3 Slide with Clyde! (number only)
Step 4 Reduce if the compound is ionic
Examples
Write formulas for the following two elements 1+
Sodium and oxygen
Sodium and nitrogen
Calcium and oxygen
Calcium and phosphorus 2- Na O Na O ≡ 2 1+ 3- Na N Na ≡ N 3 2+ 2- Ca O Ca O Ca O ≡ 2 2
reduced 2+ Ca P 3-

21. Formula Writing Rules Examples Na O Na O Na N Na N Ca O Ca O Ca O Ca P
Step 1 Write the symbols of the elements.
Step 2 Assign oxidation numbers O.N. = (P – e)
Step 3 Slide with Clyde! (number only)
Step 4 Reduce if the compound is ionic
Examples
Write formulas for the following two elements 1+
Sodium and oxygen
Sodium and nitrogen
Calcium and oxygen
Calcium and phosphorus 2- Na O Na O ≡ 2 1+ 3- Na N Na N ≡ 3 2+ 2- Ca O Ca O Ca O ≡ 2 2
reduced 2+ Ca P 3-

22. Formula Writing Rules Examples Na O Na O Na N Na N Ca O Ca O Ca O Ca P
Step 1 Write the symbols of the elements.
Step 2 Assign oxidation numbers O.N. = (P – e)
Step 3 Slide with Clyde! (number only)
Step 4 Reduce if the compound is ionic
Examples
Write formulas for the following two elements 1+
Sodium and oxygen
Sodium and nitrogen
Calcium and oxygen
Calcium and phosphorus 2- Na O Na O ≡ 2 1+ 3- Na N Na N ≡ 3 2+ 2- Ca O Ca O Ca ≡ O 2 2
reduced 2+ Ca P 3- Ca P ≡ 3 2

23. NOMENCLATURE I. Binary Ionic compounds
Binary means two different elements
Ionic means metal and nonmetal
Step 1
First give the name of the metal, followed by the
nonmetal name using the “ide” suffix.
Step 2
If the metal is to the right of group IIA, then a
Roman numeral is used after the metal to to
describe the charge of the metal. Except Ag,
Zn,and Al
Examples
NaCl Al2O3
FeCl2 FeCl3

24. NOMENCLATURE I. Binary Ionic compounds
Binary means two different elements
Ionic means metal and nonmetal
Step 1
First give the name of the metal, followed by the
nonmetal name using the “ide” suffix.
Step 2
If the metal is to the right of group IIA, then a
Roman numeral is used after the metal to to
describe the charge of the metal. Except Ag,
Zn,and Al
Examples
NaCl Sodium chloride Al2O3
FeCl2 FeCl3

25. NOMENCLATURE I. Binary Ionic compounds
Binary means two different elements
Ionic means metal and nonmetal
Step 1
First give the name of the metal, followed by the
nonmetal name using the “ide” suffix.
Step 2
If the metal is to the right of group IIA, then a
Roman numeral is used after the metal to to
describe the charge of the metal. Except Ag,
Zn,and Al
Examples
NaCl Sodium chloride Al2O3 Aluminum oxide
FeCl2 FeCl3

26. NOMENCLATURE I. Binary Ionic compounds
Binary means two different elements
Ionic means metal and nonmetal
Step 1
First give the name of the metal, followed by the
nonmetal name using the “ide” suffix.
Step 2
If the metal is to the right of group IIA, then a
Roman numeral is used after the metal to to
describe the charge of the metal. Except Ag,
Zn,and Al
Examples
NaCl Sodium chloride Al2O3 Aluminum oxide
FeCl2 Iron(II) chloride FeCl3

27. NOMENCLATURE I. Binary Ionic compounds
Binary means two different elements
Ionic means metal and nonmetal
Step 1
First give the name of the metal, followed by the
nonmetal name using the “ide” suffix.
Step 2
If the metal is to the right of group IIA, then a
Roman numeral is used after the metal to to
describe the charge of the metal. Except Ag,
Zn,and Al
Examples
NaCl Sodium chloride Al2O3 Aluminum oxide
FeCl2 Iron(II) chloride FeCl3 iron(III) chloride

28. Nonbinary means more than two different elements
II. Nonbinary Ionic compounds
Nonbinary means more than two different elements
Step 1
First give the name of the metal, followed by the memorized polyatomic ion name.
Step 2
If the metal is to the right of group IIA, then a
Roman numeral is used after the metal to describe the charge of the metal. Except Ag, Zn, and Al.
Examples
NaOH
Fe(NO3)3
Zn(C2H3O2)2
Fe(SO4)2

29. Memorized Polyatomic Ion List
Formula
Name
NH4+
Ammonium
O22-
Peroxide
C2H3O2-
Acetate
NO3-
Nitrate
CO32-
Carbonate
NO2-
Nitrite
HCO31-
Hydorgen carbonate
SO42-
Sulfate
ClO4-
Perchlorate
SO32-
Sulfite
ClO3-
Chlorate
PO43-
Phosphate
ClO2-
Chlorite
PO33-
Phosphite
ClO-
Hypochlorite
CrO42-
Chromate
CN-
Cyanide
Cr2O72-
Dichromate
OH-
Hydroxide

30. Nonbinary means more than two different elements
II. Nonbinary Ionic compounds
Nonbinary means more than two different elements
Step 1
First give the name of the metal, followed by the memorized polyatomic ion name.
Step 2 CO
If the metal is to the right of group IIA, then a
Roman numeral is used after the metal to describe the charge of the metal. Except Ag, Zn, and Al.
Examples
NaOH
Sodium hydroxide
Fe(NO3)3
Zn(C2H3O2)2
Fe(SO4)2

31. Nonbinary means more than two different elements
II. Nonbinary Ionic compounds
Nonbinary means more than two different elements
Step 1
First give the name of the metal, followed by the memorized polyatomic ion name.
Step 2
If the metal is to the right of group IIA, then a
Roman numeral is used after the metal to describe the charge of the metal. Except Ag, Zn, and Al.
Examples
NaOH
Sodium hydroxide
Fe(NO3)3
Iron(III) nitrate
Zn(C2H3O2)2
FeSO4

32. Nonbinary means more than two different elements
II. Nonbinary Ionic compounds
Nonbinary means more than two different elements
Step 1
First give the name of the metal, followed by the memorized polyatomic ion name.
Step 2
If the metal is to the right of group IIA, then a
Roman numeral is used after the metal to describe the charge of the metal. Except Ag, Zn, and Al.
Examples
NaOH
Sodium hydroxide
Fe(NO3)3
Iron(III) nitrate
Zn(C2H3O2)2
FeSO4
Iron(II) sulfate

33. Nonbinary means more than two different elements
II. Nonbinary Ionic compounds
Nonbinary means more than two different elements
Step 1
First give the name of the metal, followed by the memorized polyatomic ion name.
Step 2
If the metal is to the right of group IIA, then a
Roman numeral is used after the metal to describe the charge of the metal. Except Ag, Zn, and Al.
Examples
NaOH
Sodium hydroxide
Fe(NO3)3
Iron(III) nitrate
Zn(C2H3O2)2
Fe(SO4)2
Iron(II) sulfate
Iron(II) sulfate

34. III. Binary molecular Compounds
Molecular means nonmetals
Step 1
First give the name of the first nonmetal,
followed by the nonmetal name using the “ide” suffix.
Step 2
Give each nonmetal a Latin prefix describing
the number of atoms present in the compound.
Examples
CO CO2
P2O5 CCl4

35. You will need to learn the Greek numerical prefixes (Table 4.6):
Number
Prefix 1
Mono-* 2
Di- 3
Tri- 4
Tetra- 5
Penta- 6
Hexa- 7
Hepta- 8
Octa- 9
Nona- 10
Deca-
*Note 1
Compound
names never
start with mono
Note 2
When adding
a prefix two
vowls cannot
next to each
other

36. III. Binary Molecular Compounds
Molecular means nonmetals
Step 1
First give the name of the first nonmetal,
followed by the nonmetal name using the “ide” suffix.
Step 2
Give each nonmetal a Latin prefix describing
the number of atoms present in the compound.
Examples
CO Carbon monoxide CO2
P2O5 CCl4

37. III. Binary Molecular Compounds
Molecular means nonmetals
Step 1
First give the name of the first nonmetal,
followed by the nonmetal name using the “ide” suffix.
Step 2
Give each nonmetal a Latin prefix describing
the number of atoms present in the compound.
Examples
CO Carbon monoxide CO2 Carbon dioxide
P2O5 CCl4

38. III. Binary Molecular Compounds
Molecular means nonmetals
Step 1
First give the name of the first nonmetal,
followed by the nonmetal name using the “ide” suffix.
Step 2
Give each nonmetal a Latin prefix describing
the number of atoms present in the compound.
Examples
CO Carbon monoxide CO2 Carbon dioxide
P2O5 CCl4

39. II. Binary Ionic molecular
Molecular means combination of nonmetals
Step 1
First give the name of the first nonmetal,
followed by the nonmetal name using the “ide” suffix.
Step 2
Give each nonmetal a Latin prefix describing
the number of atoms present in the compound.
Examples
CO Carbon monoxide CO2 Carbon dioxide
P2O5 Diphosphorus Pentoxide
CCl4

40. II. Binary Ionic molecular
Molecular means combination of nonmetals
Step 1
First give the name of the first nonmetal,
followed by the nonmetal name using the “ide” suffix.
Step 2
Give each nonmetal a Latin prefix describing
the number of atoms present in the compound.
Examples
CO Carbon monoxide CO2 Carbon dioxide
P2O5 Diphosphorus Pentoxide
CCl4 Carbon tetrachloride

41. III. Nonbinary Molecular Compounds
Note: Do not use Latin prefixes
Step 1
Write down the memorized polyatomic ions present in the compound.
Step 2
Look to see if any monatomic ions are present. If so, then cations use the normal name. If it is an anion, then its name comes last with the “ide” suffix.
Examples
NH4Cl
NH4OH

42. III. Nonbinary Molecular Compounds
Note: Do not use Latin prefixes
Step 1
Write down the memorized polyatomic ions present in the compound.
Step 2
Look to see if any monatomic ions are present. If so, then cations use the normal name. If it is an anion, then its name comes last with the “ide” suffix.
Examples
NH4Cl
Ammonium chloride
NH4OH

43. III. Nonbinary Molecular Compounds
Note: Do not use Latin prefixes
Step 1
Write down the memorized polyatomic ions present in the compound.
Step 2
Look to see if any monatomic ions are present. If so, then cations use the normal name. If it is an anion, then its name comes last with the “ide” suffix.
Examples
NH4Cl
Ammonium chloride
NH4OH
Ammonium hydroxide

44. Compounds that Start with Hydrogen
Case 1
If the anion ends in “ide” and it is aqueous, then use the prefix hydro and suffix “ic acid”
Case 2
If the anion ends in “ate” then drop it and add the suffix “ic acid”
Case 3
If the anion ends in “ite” then drop it and add the suffix “ous acid”
Case 4
If the anion ends in” ide” and is a gas, or liquid, then leave the name and do not use Latin prefiex

45. Compounds that Start with Hydrogen
Examples
HCl (aq)
HNO3
HNO2
H2O (l)
HCl (g)

46. Compounds that Start with Hydrogen
Examples
HCl (aq)
chloride
HNO3
HNO2
H2O (l)
HCl (g)

47. Compounds that Start with Hydrogen
Examples
HCl (aq)
chloride
chloric acid
HNO3
HNO2
H2O (l)
HCl (g)

48. Compounds that Start with Hydrogen
Examples
HCl (aq)
chloride
chloric acid
hydrochloric acid
HNO3
HNO2
H2O (l)
HCl (g)

49. Compounds that Start with Hydrogen
Examples
HCl (aq)
Chloride
chloric acid
hydrochloric acid
HNO3
nitrate
HNO2
H2O (l)
HCl (g)

50. Compounds that Start with Hydrogen
Examples
HCl (aq)
Chloride
chloric acid
hydrochloric acid
HNO3
nitrate
nitric acid
HNO2
H2O (l)
HCl (g)

51. Compounds that Start with Hydrogen
Examples
HCl (aq)
chloride
chloric acid
hydrochloric acid
HNO3
nitrate
nitric acid
HNO2
nitrite
H2O (l)
HCl (g)

52. Compounds that Start with Hydrogen
Examples
HCl (aq)
chloride
chloric acid
hydrochloric acid
HNO3
nitrate
nitric acid
HNO2
nitrite
nitrous acid
H2O (l)
HCl (g)

53. Compounds that Start with Hydrogen
Examples
HCl (aq)
chloride
chloric acid
hydrochloric acid
HNO3
nitrate
nitric acid
HNO2
nitrite
nitrous acid
H2O (l)
oxide
HCl (g)

54. Compounds that Start with Hydrogen
Examples
HCl (aq)
chloride
chloric acid
hydrochloric acid
HNO3
nitrate
nitric acid
HNO2
nitrite
nitrous acid
H2O (l)
oxide
hydrogen oxide
HCl (g)

55. Compounds that Start with Hydrogen
Examples
HCl (aq)
chloride
chloric acid
hydrochloric acid
HNO3
nitrate
nitric acid
HNO2
nitrite
nitrous acid
H2O (l)
oxide
hydrogen oxide
HCl (g)
chloride

56. Compounds that Start with Hydrogen
Examples
HCl (aq)
chloride
chloric acid
hydrochloric acid
HNO3
nitrate
nitric acid
HNO2
nitrite
nitrous acid
H2O (l)
oxide
hydrogen oxide
HCl (g)
chloride
hydrogenchloride

57. Formula Weight Calculation
To calculate the molar mass of a compound we sum together the atomic weights of the atoms that make up the formula of the compound. This is called the formula weight (MW, M).
Formula weights are the sum of atomic weights of atoms
Making up the formula.
The following outlines how to find the formula weight of water
symbol
weight
number H
1.01 X 2 =
2.02 O
16.0 X 1 =
16.0
18.0
g/mole

58. Percent Composition
Find the formula weight and the percent composition of
glucose (C6H12O6)
symbol
weight
number
72.0 C
12.0 x 6 = H
1.01 x 12 =
12.12 O
16.0 x 6 =
96.0
180.1 g/mole
72.0
%C =
X =
40.0 %C
180.1
12.12
%H =
X =
6.73 %H
180.1
96.0
X =
53.3 %O
%O =
180.1

59. “the mass of one mole of that substance.”
Formula Weight
We can define the molar mass or molecular weight of a substance can as:
“the mass of one mole of that substance.”
We give molar mass the symbol M and it has units g/mol-
For an atom the molar mass is equal to the atomic weight we find on the period table.

60. Its All About Moles
For a molecule the molecular weight is equal to the sum of the atomic weights of the atoms that make it up.
The mathematical relationship between mass and moles is:
m = nM
This can be summarized by the following diagram:
moles

61. Mole Concepts The key equation to remember for mole calculations is:
m = nM
Where:
M = molecular weight (gmol-1)
n = number of moles (mol)
m = mass of sample (g)

62. Mole Concepts
For a mole of a molecule the number of moles of each atom is determined by how many of that atom are in each molecule.
e.g. One mole of H2O contains:
One mole of oxygen atoms
Two moles of hydrogen atoms
In 5 moles of H2SO4 how many moles of oxygen atoms is there?
20 moles of O atoms.

63. Mole Conversions
In 50.0g of H2SO4 how many moles of oxygen atoms are there?
50.0g of H2SO4

64. Mole Conversions
In 50.0g of H2SO4 how many moles of oxygen atoms are there?
50.0g of H2SO4
mole H2SO4 =
98.0g of H2SO4

65. Mole Conversions
In 50.0g of H2SO4 how many moles of oxygen atoms are there?
50.0g of H2SO4
mole H2SO4
4mole O =
2.04 mole O
mole H2SO4
98.0g of H2SO4

66. Mole Conversions
In 5 moles of H2SO4 how many atoms of oxygen are present?

67. Mole Conversions
In 5 moles of H2SO4 how many atoms of oxygen are present?
5 moles H2SO4 =

68. Mole Conversions
In 5 moles of H2SO4 how many atoms of oxygen are present?
5 moles H2SO4
4 mole O
mole H2SO4

69. Mole Conversions
In 5 moles of H2SO4 how many atoms of oxygen are present?
5 moles H2SO4
4 mole O
6.02 x 1023 atoms O =
mole H2SO4
mole O
1.20 x 1025 atoms

70. Empirical Formulas
Empirical formula is the smallest whole number ratio between atoms and can be calculated from the percent composition.
Molecular formulas happen to be the exact number of atoms making up a molecule, and may or may no be the simplest whole number ratio. Molecular formulas are whole number multiples of the empirical formula.

71. Empirical Formula Steps
Assume 100 g of compound.
Convert percent to a mass number.
Convert the mass to moles.
Divide each mole number by the smallest mole number.
Rounding:
If the decimal is ≤ 0.1, then drop the decimals
If the decimal is ≥0.9, then round up.
All other decimal need to be multiplied by a whole number until roundable.

72. Empirical Formula Example
A compound is composed of 75.0% C and 25.0% H. Find its empirical formula.
Step #1 Assume 100 g of compound
75.0 g C
25.0 g H

73. Empirical Formula Example
A compound is composed of 75.0% C and 15.0% H. Find its empirical formula.
Step #2 Convert grams to moles.
Mole C
75.0 g C
= mole C
12.01 g
25.0 g H
Mole H
= mole H
1.008 g H

74. Empirical Formula Example
A compound is composed of 75.0% C and 15.0% H. Find its empirical formula.
Step #3 Divide each mole number by the smallest.
Mole C
75.0 g C
= mole C
12.01 g
25.0 g H
Mole H
= mole H
1.008 g H
6.225
24.802
= 1.00
= 3.98
6.225
6.225

75. Empirical Formula Example
A compound is composed of 75.0% C and 15.0% H. Find its empirical formula.
Step #4 Rounding; Decimal ≤ 0.1, drop decimals
Mole C
75.0 g C
= mole C
12.01 g
25.0 g H
Mole H
= mole H
1.008 g H
6.225
24.802
= 1.00
= 3.98
6.225
6.225

76. Empirical Formula Example
A compound is composed of 75.0% C and 15.0% H. Find its empirical formula.
Step #4 Rounding; Decimal ≤ 0.1, drop decimals
Mole C
75.0 g C
= mole C
12.01 g
25.0 g H
Mole H
= mole H
1.008 g H
6.225
24.802
= 1 C
= 3.98
6.225
6.225

77. 6-8 Empirical Formula Example
A compound is composed of 75.0% C and 15.0% H. Find its empirical formula.
Step #4 Rounding; Decimal ≥ 0.9, round up
Mole C
75.0 g C
= mole C
12.01 g
25.0 g H
Mole H
= mole H
1.008 g H
6.225
24.802
= 1 C
= 3.98
6.225
6.225

78. Empirical Formula Example
A compound is composed of 75.0% C and 15.0% H. Find its empirical formula.
Step #4 Rounding; Decimal ≥ 0.9, round up
Mole C
75.0 g C
= mole C
12.01 g
25.0 g H
Mole H
= mole H
1.008 g H
6.225
24.802
= 1 C
= 3.98
6.225
6.225

79. Empirical Formula Example
A compound is composed of 75.0% C and 15.0% H. Find its empirical formula.
Step #4 Rounding; Decimal ≥ 0.9, round up
Mole C
75.0 g C
= mole C
12.01 g
25.0 g H
Mole H
= mole H
1.008 g H
6.225
24.802
= 1 C
= 4 H
6.225
6.225

80. Empirical Formula Example
A compound is composed of 75.0% C and 15.0% H. Find its empirical formula.
Step #4 Rounding; Decimal ≥ 0.9, round up
Mole C
75.0 g C
= mole C
12.01 g
25.0 g H
Mole H
= mole H
1.008 g H
6.225
24.802
= 1 C
= 4 H
6.225
6.225
Empirical Formula = CH4

81. Molecular Formulas
Empirical formula, is the smallest ratio between atoms in a molecular or formula unit.
Molecular formula, is the exact number of atoms in a molecule; a whole number multiple of an empirical formula

82. Possible Molecular Formulas
Assume an empirical formula of C3H5O
Empirical formula
Integer
Molecular Formula
C3H5O
C3H5O 1 2 3 4 5
C3H5O
C3H5O
C3H5O
C3H5O

83. 6-9 Possible Molecular Formulas
Assume an empirical formula of C3H5O
Empirical formula
Integer
Molecular Formula
C3H5O
C3H5O 1 2 3 4 5
C3H5O
C6H10O2
C3H5O
C3H5O
C3H5O

84. Possible Molecular Formulas
Assume an empirical formula of C3H5O
Empirical formula
Integer
Molecular Formula
C3H5O
C3H5O 1 2 3 4 5
C3H5O
C6H10O2
C9H15O3
C3H5O
C3H5O
C3H5O

85. Possible Molecular Formulas
Assume an empirical formula of C3H5O
Empirical formula
Integer
Molecular Formula
C3H5O
C3H5O 1 2 3 4 5
C3H5O
C6H10O2
C9H15O3
C3H5O
C3H5O
C12H20O4
C3H5O
C15H25O5

86. Sample Problem
Calculate the molecular formula of a molecule composed of 83.7%C and 16.3% H, with a molar mass of 86.0 g/mole

87. Sample Problem
Calculate the molecular formula of a molecule composed of 83.7%C and 16.3% H, with a molar mass of 86.0 g/mole
Step #1 Assume 100g of compound
83.6 g C
16.3 g H

88. Sample Problem
Calculate the molecular formula of a molecule composed of 83.7%C and 16.3% H, with a molar mass of 86.0 g/mole
Step #2 Convert grams to moles
83.6 g C
mole
12.01 g C
16.3 g H
mole
1.008 g H

89. Sample Problem
Calculate the molecular formula of a molecule composed of 83.7%C and 16.3% H, with a molar mass of 86.0 g/mole
Step #2 Convert grams to moles
83.6 g C
mole
= mole
12.01 g C
16.3 g H
mole
= mole
1.008 g H

90. Sample Problem
Calculate the molecular formula of a molecule composed of 83.7%C and 16.3% H, with a molar mass of 86.0 g/mole
Step #3 Divide each mole number by the smallest.
83.6 g C
mole
= mole
12.01 g C
16.3 g H
mole
= mole
1.008 g H

91. Sample Problem
Calculate the molecular formula of a molecule composed of 83.7%C and 16.3% H, with a molar mass of 86.0 g/mole
Step #3 Divide each mole number by the smallest.
6.961
83.6 g C
mole
= 1.00
= mole
6.961
12.01 g C
16.3 g H
mole
= mole
= 2.32
1.008 g H

92. Sample Problem
Calculate the molecular formula of a molecule composed of 83.7%C and 16.3% H, with a molar mass of 86.0 g/mole
Step #4 Round if---Not Roundable
6.961
83.6 g C
mole
= mole
= 1.00
6.961
12.01 g C
16.3 g H
mole
= mole
= 2.32
1.008 g H
Step #4, Multiply by an integer until roundable
1.00 X 3 = 3
2.32 X 3 = 7
Empirical formula C3H7

93. Molecular Formula Integer
Divide empirical weight into molecular weight
3x12 + 7x1 =43 2 43 86
Now multiply the empirical formula by 2

94. Molecular Formula Integer
Divide empirical weight into molecular weight
3x12 + 7x1 =43 2 43 86
Now multiply the empirical formula by 2
Molecular Formula is C6 H14

95. The End