1. Elements and Compounds
elements combine together to make an almost limitless number of compounds
the properties of the compound are totally different from the constituent elements
H2(g) + O2(g)  H2O(l)
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3. Tro, Chemistry: A Molecular Approach

4. Formation of Water from Its Elements
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5. Allotropes:one of two or more forms of an element that differ in their basic structure
diamond
graphite
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6. Allotropes of carbon diamond graphite
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7. Allotrope of carbon

8. Chemical Bonds
compounds : made of atoms held together by chemical bonds
Bonds:forces of attraction between atoms
attractions between protons and electrons
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9. Bond Types two general types of bonding ionic and covalent
ionic bonds electrons transferred between atoms, results in oppositely charged ions that attract each other
Metals + nonmetal
covalent bonds two atoms share some of their electrons
Nonmetal + nonmetal
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11. Molecular View of Elements and Compounds
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12. Homonuclear vs heteronuclear
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13. Molecular Elements H2 Cl2 Br2 I2 N2 O2 F2
Certain elements occur as 2 atom molecules
Rule of 7’s
Other elements occur as polyatomic molecules
P4, S8, Se8 H2
Cl2
Br2 I2 7 7A
N2 O F2
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14. Classifying Materials
atomic elements = Fe
molecular elements = N2
molecular compounds = H2O
ionic compounds = SrCl2 MgCO3
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15. Representing Compounds with Chemical Formula
compounds represented with: chemical formula
Type of formula determines amount of information given

16. Types of Formula Empirical Formula
Tells atoms and their ratio
do not describe how many atoms, the order of attachment, or the shape
the formulas for ionic compounds are empirical

18. Empirical formula Empirical formula Molecular formula HO __________
C8H8
C6H12O6
_________
Hg2Cl2

19. Types of Formula

20. Expanded structural formula vs. condensed structural formula

21. Formula Mass
the mass of an individual molecule or formula unit (FW) amu (D for Dalton)
molecular mass or molecular weight (MW or μ) g/mol
sum of the masses of the atoms in a single molecule or formula unit
mass of 1 molecule of H2O
= 2(1.01 amu H) amu O = amu
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22. What Is a Mole?
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24. How Big is a Mole?
N=6.022x1023
One mole of Marshmallows would cover the entire earth 12 miles high
One mole of marshmallows would fill the Grand Canyon and still be enough left over to displace all the water from Lake Michigan and more

25. Mole = 6.022x1023items Avogadro’s number N

26. Molar Mass of Compounds
the relative masses of molecules can be calculated from atomic masses
Formula Mass = 1 molecule of H2O
= 2(1.01 amu H) amu O = amu
since 1 mole of H2O contains 2 moles of H and 1 mole of O
Molar Mass = 1 mole H2O
= 2(1.01 g H) g O = g
so the Molar Mass of H2O is g/mole
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27. Moles as Conversion factors
Moles to molecules or atoms
Use Avogadro’s number
Ex: How many molecules of water are in 9.01 g of water?
Grams to moles
Use Molar Mass
Ex: How many moles are in 9.01 g of water?

28. Moles How many molecules of Chlorine are in 19.5 grams of chlorine?
How many moles of sodium atoms is 29.0 grams of sodium?
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29. Tro, Chemistry: A Molecular Approach

30. Molecular formula In 5.0 moles of the compound Mg(H2PO4)2
How many moles of Mg are there?____
How many moles of phosphorus are there?___
How many moles of oxygen are there?______
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31. Molar mass
What is the formula weight (FW) of Mg(H2PO4)2 including units? ________
What is the molar mass (MW or µ) of Mg(H2PO4)2 including units?_________
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32. Practice - Converting Grams to Molecules
How many molecules are in 50.0 g of PbO2?
(PbO2 = g/mol)
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33. Percent Composition Percentage of each element in a compound
Mass of element/mass of compound
The percentages may not always total to 100% due to rounding
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34. Find the mass percent of Cl in CCl2F2

35. Mass Percent as a Conversion Factor
the mass percent tells you the mass of a constituent element in 100 g of the compound
the fact that CCl2F2 is 58.64% Cl by mass means that 100 g of CCl2F2 contains g Cl
this can be used as a conversion factor
100 g CCl2F2 : g Cl

36. Example 3.14 – Find the mass of table salt containing 2.4 g of Na
Given:
Find:
2.4 g Na, 39% Na
g NaCl
Concept Plan:
Relationships:
100. g NaCl : 39 g Na
g Na
g NaCl
Solution:
Check:
since the mass of NaCl is more than 2x the mass of Na, the number makes sense

37. Benzaldehyde is 79. 2% carbon. What mass of benzaldehyde contains 19
Benzaldehyde is 79.2% carbon. What mass of benzaldehyde contains 19.8 g of C?

38. Empirical Formula
simplest, whole-number ratio of the atoms of elements in a compound
can be determined from elemental analysis
masses of elements formed when decompose or react compound
combustion analysis
percent composition
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39. Finding an Empirical Formula
convert the percentages to grams
assume you start with 100 g of the compound
skip if already in grams
convert grams to moles
use molar mass of each element
write a pseudoformula using moles as subscripts
divide all by smallest number of moles
if result is within 0.1 of whole number, round to whole number
multiply all mole ratios by number to make all whole numbers
if ratio ?.5, multiply all by 2; if ratio ?.33 or ?.67, multiply all by 3; if ratio 0.25 or 0.75, multiply all by 4; etc.
skip if already whole numbers
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40. Calculating Empirical formula
1. A sample of an unknown compound with a mass of g was found to contain g of carbon and g of oxygen. What is its empirical formula?

41. Calculating empirical formula
An oxide of iron called black iron oxide, is analyzed. In a g sample the ore was found to contain g of Fe and g of O. Calculate the empirical formula of this compound

42. Example 3.17
Laboratory analysis of aspirin determined the following mass percent composition. Find the empirical formula.
C = 60.00%
H = 4.48%
O = 35.53%

43. Finding empirical formula
C, H, O
mol
C, H, O
mol
ratio
empirical
formula
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44. Determine the empirical formula of hematite, which contains 72
Determine the empirical formula of hematite, which contains 72.4% Fe (55.85) and the rest oxygen (16.00)
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45. Molecular Formulas
The molecular formula is a multiple of the empirical formula
To determine the molecular formula you need to know the empirical formula and the molar mass of the compound

46. Example 3.18 – Find the molecular formula of butanedione
empirical formula for butanedione = C2H3O;
MW of molecular formula = g/mol

47. Benzopyrene has a molar mass of 252 g/mol and an empirical formula of C5H3. What is its molecular formula? (C = 12.01, H=1.01)

48. hydrates

49. Hydrates
When the hydrate of RuCl3 is heated water is driven off to form the anhydrous salt as shown below:
RuCl3.xH2O  RuCl xH2O
If g of hydrated compound is heated and g of anhydrous salt remains what is the value of x?

50. Naming hydrates:
name the ionic compound then the water part, use prefixes for number of water molecules
Ionic formula • x H2O
x = prefix (di, tri etc from covalent naming)
H2O = hydrate
Ex:   CuSO4• 5 H2O   copper(II) sulfate pentahydrate
Ex.   CaCl2• 2 H2O   calcium chloride dihydrate

51. Combustion Analysis

52. Example 3.20
Combustion of a g sample of a compound containing only carbon, hydrogen, and oxygen produced the following:
CO2 = g
H2O = g
Determine the empirical formula of the compound
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53. Write a Concept Plan: g CO2, H2O mol CO2, H2O mol C, H g C, H g O mol
C, H, O
mol
ratio
empirical
formula

54. Information
Given: g compound, g CO2, g H2O,
Find: Empirical Formula, CxHyOz
mol C, g C, mol H, g H, g O, mol O
Plan: g CO2 & H2O  mol CO2 & H2O  mol C & H 
g C + H  g O  mol O  mol ratio  emp. formula
Example 3.20: Find the empirical formula of compound with the given amounts of combustion products
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55. The smell of dirty gym socks is caused by the compound caproic acid
The smell of dirty gym socks is caused by the compound caproic acid. Combustion of g of caproic acid produced g of H2O and g of CO2. If the molar mass of caproic acid is g/mol, what is the molecular formula of caproic acid? (μ C = 12.01, H = 1.008, O = 16.00)

56. C H O g
0.524
0.0877
0.232
moles
0.0436
0.0870
0.0145
C0.0436H0.0870O0.0145
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57. Molecular Formula = {C3H6O} x 2 = C6H12O2
Tro, Chemistry: A Molecular Approach

58. 1. Nicotine, a poisonous compound found in tobacco leaves, is 74
1. Nicotine, a poisonous compound found in tobacco leaves, is 74.0% C, 8.65% H, and 17.35% N. It has a molar mass of 162 g/mol.
What is the molecular formula of nicotine?
2. The “average” cigarette in the US contains 9.0 mg of nicotine but during smoking about 90% of the nicotine is burned off.
How many molecules of nicotine are inhaled during smoking of one “average” cigarette?

60. Other fun things to do
with moles
Molarity

61. What is the molarity of a solution prepared by dissolving 15
What is the molarity of a solution prepared by dissolving 15.0 g of sodium hydroxide in enough water to make a total of 225 mL of solution?

62. Practice Problems
What is the molarity of a solution that contains moles of H2SO4 in 2.50 L of solution?
2. What is the molarity of a solution prepared by dissolving 25.0 g of HCl (g) in enough water to make mL of solution?

63. How would you prepare 1 liter of a 0
How would you prepare 1 liter of a 0.25 M (molar) solution of glucose (C6H12O6) (molar mass 180 g/mol)?