1. Stoichiometry
AKA Chemistry Math

2. How many atoms are in a mole of carbon?
BELL RINGER
“my avogadro don't want none unless you've got moles hun”
How many atoms are in a mole of carbon?

3. Intro to the Mole How many are in a dozen? How many are in a gross?
How many is a ream?
How many reams are 5000 sheets of paper?
What is a score?
“Four score and 7 years ago”

4. Ridiculous Mole Facts
3 moles of M&M’s would fill the entire earths oceans (an equivalent amount of water would fill about a ¼ cup)
1 mole of donut holes will cover the earth to a depth of seven miles!
1 mole of pennies would reach to the moon 7-8 times.

5. A one liter bottle of water contains 55.5 moles of water.
Ridiculous Mole Facts
One mole of seconds is about 19 quadrillion years, 4,240,666 times the age of the earth, or 954,150 times the age of the universe itself.
A one liter bottle of water contains 55.5 moles of water.
If you started with a mole of pennies and spent $1,000,000 every second for 100 years, you would still have more than 99.99% of what you started with. 

6. Are all moles created equally?VS
In chemistry, how an atom reacts is dependent on the number of atoms, not the mass of the atoms.

7. A nice mole song!
Avogadro Style

8. Is it feasible to count atoms?
Look at the mole of salt and a mole sugar
Did I count the particles of each to know I had a mole?
What is a property of the salt or sugar that I could measure?
Mass
And that’s where this number comes from. Since it’s not practical to count atoms, scientists decided to find a way to relate the atomic mass of one atom of an element to an amount of that element in grams. That’s where the mole comes in – they set 1 mole equal to the number of atoms of carbon present in grams of C-12. This number was then determined experimentally to be 6.02*1023.

9. That would be 6.02 x 1023 atoms of carbon
Moles
What is the mass of a Carbon atom?
12.0 amu
If one mole of Carbon atom’s have a mass of 12.0g, how many atoms would that be?
That would be 6.02 x 1023 atoms of carbon

10. Gram Formula Mass (molar mass)
= the mass of one mole of something
Let’s try out water:
H2O
Therefore, 1 mole of water has a mass of 18g/mol. H 2
x 1.0
= 2.0 = O 1 x
18.0 g/mol

11. GFM (practice) Let’s try magnesium hydroxide: Mg(OH)2 Mg 1 x 24.3= O 2 x = H 2 x =
58.3 g/mol

12. GFM - Hydrates Na2CO3●10H20 Sodium Carbonate crystals: Na 2 x 23.0
Hydrate - is a crystalline compound in which ions are attached to one or more WATER molecules
Na2CO3●10H20
Sodium Carbonate crystals: Na 2 x = C 1 x = 3 x =
H20 10 x =
286.0 g/mol

13. # of atoms 1.11 x 1024 1.84 moles of S = ____________ atoms 1.84 moles
6.02 x 1023 atoms x = 1
1.00 mol
3.24 moles of K = ____________ atoms
1.11 x 1024
1.95 x 1024
3.24 moles
6.02 x 1023 atoms x = 1
1.00 mol

14. “my avogadro don't want none unless you've got moles hun”
BELL RINGER
“my avogadro don't want none unless you've got moles hun”
What is the gfm of NH4+?
GFM = 18 Moles = 72.0 ÷ 18.0 = 4 moles

15. Converting to moles 1. Determine the gfm: 18.0 g/mol
If you have 63.0g of water how many moles of water do you have?
1. Determine the gfm:
18.0 g/mol
Number of moles
given mass (g)
gram-formula mass =
Number of moles
63.0g
18.0g/mol =
= moles

16. Conversions Moles to Grams
1. How many g are in moles of H2O2?
Number of moles
given mass (g)
gram-formula mass =
2. How many g are in 1.20 moles of CaCO3?

17. Percent Composition What are the % of elements in dihydrogen monoxide?
-used to find the percentage by mass of an element in a compound
What are the % of elements in dihydrogen monoxide?
H2O H 2
x 1.0
= 2.0
%= 2.0/18.0 = 11% 1
x 16.0
= 16.0 O
%= 16.0/18.0 = 88.9%
18.0 g

18. Percent Composition What are the % of elements in potassium nitrate?
KNO3 K 1
x 39.1 =
% = /101.1 = 38.7% N 1
x 14.0
= 14.0
% = /101.1 = 13.8% = O 3
x 16.0
% = 48.0/101.1 = 47.5%
101.1 g

19. Hydrate Percent Composition
What is the percentage of water in the following compound
CoCl2•6H2O Co 1
x 58.9
= 58.9
% = /237.9 = 24.8% Cl 2
x 35.5
= 71.0
% = /237.9 = 29.8%
= 108.0
H2O 6
x 18.0
% = 108.0/237.9 = 45.40%
237.9 g/mol

20. Hydrate Percent Composition CaSO4•5H2O
What is the percentage of water in the following compound
CaSO4•5H2O Ca 1
x 40.1
= 40.1 S 1
x 32.1
= 32.1 O 4
x 16.0
= 64.0
H2O 5
x 18.0
= 90.0
% = 90.0/226.2 = 39.8%
226.2 g/mol

21. Some Practice What is the gfm for Calcium nitrate? Ca 1 x 40.1 = 40.1
Criss-cross to get the formula:
Ca(NO3)2 Ca 1 x = N 2 x = O 6 x =
164.1 g/mol
2. How many moles of calcium nitrate do you have if you have 10.2 g?
Number of moles
given mass (g)
gram-formula mass =
Number of moles
10.2g
164.1g/mol =
= moles

22. Practice Problems GFM = 122.6 g GFM = 122.6 g
1. If you have 40.8g of KClO3. How many moles do you have?
GFM = g
Number of moles
given mass (g)
gram-formula mass =
Number of moles
40.8 g
122.6g =
= moles
2. You have 2.5 moles of KClO3. How many grams is that?
GFM = g
Grams = GFM x # moles
Grams = 122.6g/mol x 2.5 moles
= g
= 310 g

23. How many grams is 0.36 moles of potassium permanganate?
BELL RINGER
How many grams is 0.36 moles of potassium permanganate?

24. You have .0774g of NH4+. How many moles do you have?
BELL RINGER
You have .0774g of NH4+. How many moles do you have?
GFM = 18.0 Moles = ÷ 18.0 =
moles

25. Empirical and Molecular Formulas
Molecular Formula = the formula of a compound in which the subscripts give the actual number of each element in the formula
Ethane – C2H4
Empirical Formula – represents the simplest ratio in which atoms combine to form a compound
▪ the reduced version of a formula
Ethane – C2H4
 CH2
The ratio of C:H is _____.
1:2
It is also moles.

26. Calculating Molecular Formulas
A compound has the empirical formula of CH2 and a molecular mass of 42.0 g. What is its molecular formula?
Step 1 – Determine the gram atomic mass of the empirical formula. C 1
x 12.0g
= 12.0
= 14.0g H 2
x 1.0g
= 2.0
Step 2 – Get the ration between the molecular mass and the gfm of the empirical formula.
42.0 g ÷ 14.0 g
= 3
Step 3 – Multiply the subscripts of the empirical formula by the ratio, we have the molecular formula
CH2
X 3
= C3H6

27. Calculating Molecular Formulas
What is the molecular formula of a compound that has a molecular mass of 92.0 g and an empirical formula of NO2 ?
= N2O4
A compound contains 0.50 mole of carbon for each 1.00 mole of hydrogen. What is the empirical formula of the compound?
1) CH 2) CH2 3) C2H 4) C2H2

28. Calculating Empirical Formulas
A sample of a compound contains 24 g of carbon and 64 g of oxygen. What is the empirical formula of the compound?
Step 1 – The subscripts in cmpd represent moles, so we need to figure out how many moles we have of each element. C
24 g
÷ 12.0g
= 2.0 mol O
64 g
÷ 16.0g
= 4.0 mol
Step 2 – Write out the molecular formula using what you just obtained.
C2O4
Step 3 – Reduce the molecular formula if possible.
CO2

29. Calculating Empirical Formulas
A sample contains 156 g of potassium and 64g of sulfur. What is the empirical formula of this compound?
Step 1 – The subscripts in cmpd represent moles, so we need to figure out how many moles we have of each element. K
156 g
÷ 39.1g
= 3.99 mol
 4 mol S
64 g
÷ 32.1g
= 1.99 mol
 2 mol
Step 2 – Write out the molecular formula using what you just obtained.
K4S2
Step 3 – Reduce the molecular formula if possible.
K2S

30. Popcorn Lab

31. Empirical and Molecular Formulas
Empirical Formula
H2O
CH3COOH
CH2OH
WO2
B2H6
C6H12O6
H2O
CH2O
CH2OH
WO2
BH3
CH2O

32. Empirical and Molecular Formulas
A compound with an empirical formula of C2OH4 and a molar mass of 88 grams per mole. What is the molecular formula of the compound?

33. Empirical and Molecular Formulas
A well known reagent in analytical chemistry, dimethylglyoxime, has the empirical formula C2H4NO. If its molar mass is 116.1g/mol, what is the molecular formula of the compound?

35. BELL RINGER
What are the empirical formulas for the following? C6H6 CH2ClCH3 HC2H3O2

36. Determining Formulas from %
Percent to mass
Mass to moles
Divide by small
Multiply ‘til whole
A compound consists of 72.2% magnesium and 27.8% nitrogen by mass. What is the empirical formula?
1. Assume 100g, so you have: 72.2g Mg and 27.8g N
2. Convert to moles
Mg /24.3
= 2.97 moles
N – 27.8/14.0
= 1.99 moles

37. Determining Formulas from %
Percent to mass
Mass to moles
Divide by small
Multiply ‘til whole
3. Divide by small
Mg / 1.99
= 1.49
Mg1.49N1.00 ???
N / 1.99
= 1.00
4. Multiply ‘til whole
Mg 1.49
X 2 = 3
Mg3N2
N 1
X 2 = 2

38. Hydrate Problem
In lab, a student determined that a hydrate of barium chloride contained 14.0% water. What is the actual numbers of water molecules for each molecule of barium chloride. Basically the formula of the hydrate.
REMEMBER

39. Hydrate Problem
Barium Chloride
Water
14.0%

40. Hydrate Lab

41. BELL RINGER
Problem: A compound contains 32.4% sodium, 22.1% sulfur and 45.0% oxygen. What is the empirical formula?
Na 32.4g
S 22.1g
O 45.0g
÷ 23.0
÷ 32.1
÷ 16.0
= 1.41 mol
= mol
= 2.81 mol
÷ .688
= 2.05
= 1.00
= 4.09
As a result the formula would be:
Na2SO4

42. 3.56 g. Use this information to determine the formula for the hydrate.
Hydrate Practice
A calcium chloride hydrate has a mass of 4.72 g. After heating for several minutes the mass of the anhydrate is found to be
3.56 g. Use this information to determine the formula for the hydrate.

43. Hydrate Practice (lab problem)
Mass of Hydrate = 4.72g
Anhydrous = 3.56g
Calcium Chloride
Water

44. CHEMICAL REACTIONS
Reactants: Zn + I2
Product: Zn I2

45. Chemical Equations
Because of the principle of the law conservation of matter,
an equation must be balanced.
It must have the same number of each kind of atoms on both sides.
Lavoisier
1788

46. Al (s) + O2 (g) ---> Al2O3 (s)
Chemical Equations
Their Job: Depict the kind of reactants and products and their relative amounts in a reaction.
Al (s) O2 (g) ---> Al2O3 (s)
The numbers in the front are called
stoichiometric ____________ 4 3 2
coefficients

47. Symbols Used in Equations
Solid (s)
Liquid (l)
Gas (g)
Aqueous solution (aq)
Catalyst H2SO4
Escaping gas ()
Change of temperature ()

48. but you may not change the subscripts.
Balancing Equations
When balancing a chemical reaction you may add coefficients in front of the compounds to balance the reaction -
but you may not change the subscripts.
Changing the subscripts changes the compound. Subscripts are determined by the valence electrons (charges for ionic or sharing for covalent)

49. Subscripts vs. Coefficients
The subscripts tell you how many atoms of a particular element are in a compound. The coefficient tells you about the quantity, or number, of molecules of the compound.

50. Why are we learning this?
The coefficients of a chemical reaction indicate relative amounts of reactants and products.
Coefficients are MOLE RATIOS
Example: H2(g) + Cl2(g)  2HCl(g)
1 mol H2 : 1 mol Cl2 : 2 moles HCl
The relative masses of the reactants and products can also be determined from the coefficients.
Example:
1 mol H2 = 2.02 g H2
1 mol Cl2 = g Cl2
2 mol HCl = g HCl
Therefore, 2.02g H2 will react with 70.90g Cl2 to form 72.92g of HCl.

51. Steps to Balancing Equations
Compare the numbers of atoms on each side of the equation
Start with the most complicated molecules FIRST!
Leave H and O until the end
Place COEFFICIENTS in front of the compound to try and balance the atoms
Check your answer to see if:
- The numbers of atoms on both sides of the equation are now balanced.
Reduce if possible!!!!

52. Steps to Balancing Equations2 3
___ Al(s) + ___ Br2(l) ---> ___ Al2Br6(s)

53. Online Balancing Equations
Click on picture above to go to the site!

54. Balancing Equations 5
____C3H8(g) _____ O2(g) > _____CO2(g) _____ H2O(g) 3 4
____B4H10(g) _____ O2(g) > ___ B2O3(g) _____ H2O(g) 2 11 4 2 10 5

55. KMnO4 + HCl = KCl + MnCl2 + H2O + Cl2
K4Fe(CN)6 + H2SO4 + H2O = K2SO4 + FeSO4 + (NH4)2SO4 + CO
C6H5COOH + O2 = CO2 + H2O
K4Fe(CN)6 + KMnO4 + H2SO4 = KHSO4 + Fe2(SO4)3 + MnSO4 + HNO3 + CO2 + H2O
Cr2O7{-2} + H{+} + {-} = Cr{+3} + H2O
S{-2} + I2 = I{-} + S
PhCH3 + KMnO4 + H2SO4 = PhCOOH + K2SO4 + MnSO4 + H2O
CuSO4*5H2O = CuSO4 + H2O

56. Balancing Equations 2 2 ___ H2(g) + ___ O2(g) ---> ___ H2O(l)
What Happened to the Other Oxygen Atom?????
This equation is not balanced!
Two hydrogen atoms from a hydrogen molecule (H2) combines with one of the oxygen atoms from an oxygen molecule (O2) to form H2O. Then, the remaining oxygen atom combines with two more hydrogen atoms (from another H2 molecule) to make a second H2O molecule.

57. BELL RINGER
Balance the following: Sodium phosphate + iron (III) oxide  sodium oxide + iron (III) phosphate 2
Na3PO4 + Fe2O3 ----> Na2O FePO4 3 2

58. Balance the following: Ca(OH)2 + H3PO4 → Ca3(PO4)2 + H2O
BELL RINGER
Balance the following: Ca(OH)2 + H3PO4 → Ca3(PO4)2 + H2O

59. Balancing wkst

60. Practice Balancing Equations2
__Al + __O2  __Al2O2
__ Fe + __Cl2  __ FeCl3 2 3 2 3
__Fe2O3 + __H2SO4  __Fe2(SO4)3 + __H2O 3
__KClO3 → __KCl + __O2 2 2 3

61. Methane reacts with oxygen to produce carbon dioxide and water
Practice
Write out the following chemical equation 
Methane reacts with oxygen to produce carbon dioxide and water
CH4 + O2 
CO2 +
H2O

62. Practice H2(g) + O2(g)  + H2O(l) energy
Write out the following chemical equation 
Hydrogen gas reacts in the presence of oxygen gas to explode and produce liquid water.
H2(g) +
O2(g) 
H2O(l) +
energy

63. What is the IUPAC name of the following compound? Mn2O3
BELL RINGER
What is the IUPAC name of the following compound? Mn2O3

64. Chemical Equations 4 Al(s) + 3 O2(g) ---> 2 Al2O3(s)
This equation means
4 Al atoms + 3 O2 molecules ---produces--->
2 molecules of Al2O3
AND/OR
4 moles of Al + 3 moles of O produces--->
2 moles of Al2O3

65. Types of Reactions
There are five types of chemical reactions we will talk about:
Synthesis reactions
Decomposition reactions
Combustion reactions
Single replacement reactions
Double Replacement reactions
You need to be able to identify the type of reaction and predict the product(s)

66. Zn powder + Sulfur – See Hilt
1. Synthesis Reactions
Synthesis reactions occur when two substances (generally elements) combine and form a compound. (Sometimes these are called combination or addition reactions.)
reactant + reactant  1 product
Basically: A + B  AB
Example: 2H2 + O2  2H2O
Example: C + O2  CO2
DEMO: Write the reaction for the synthesis of MgO(s)
Mg(g) + O2(g)  MgO(s) 2
Zn powder + Sulfur – See Hilt

67. 2. Decomposition Reactions
Decomposition reactions occur when a compound breaks up into the elements or in a few to simpler compounds
1 Reactant  Product + Product
In general: AB  A + B
Example: 2 H2O  2H2 + O2
Example: 2 HgO 
2Hg + O2

68. Decompostion of KBrO3 – See Hilt
Elephant’s Toothpase
Write the reaction for the decomposition of hydrogen peroxide (H2O2)
H2O2  H2O O2 2
Decompostion of KBrO3 – See Hilt

69. Practice
Predict the products. Then, write and balance the following decomposition reaction equations:
Solid Lead (IV) oxide decomposes
The formation of sulfur dioxide
PbO2(s) 
Pb + O2
S +
O2 
SO2

70. 3. Combustion Reactions Combustion is actually an organic reaction
Organic Compound + O2  CO2 + H2O
Methane Mamba
CH4
+ O2
 CO2
+ H2O

71. BELL RINGER
Write and balance the following: Decomposition of ammonia Formation of calcium chloride

72. 4. Single Replacement Reactions
Single Replacement Reactions occur when one element replaces another in a compound.
A metal can replace a metal (+) OR a nonmetal can replace a nonmetal (-).
Must refer to Table J
element + compound different element + different compound
A + BC  AC + B (if A is a metal) OR
A + BC  BA + C (if A is a nonmetal)
(remember the cation(+) always goes first!)
When H2O splits into ions, it splits into
H+ and OH- (not H+ and O-2 !!)

73. Aluminum metal reacts with aqueous copper (II) nitrate
Practice
Sodium chloride solid reacts with fluorine gas
NaCl(s) + F2(g)  2
NaF(s) + Cl2(g)
Aluminum metal reacts with aqueous copper (II) nitrate
Al(s) + 2 3
Cu(NO3)2 (aq) 
Cu + 3 2
Al(NO3)3

74. 5. Double Replacement Reactions
Double Replacement Reactions occur when a metal replaces a metal in a compound and a nonmetal replaces a nonmetal in a compound
Compound + compound  product + product
AB + CD  AD + CB

75. Double Replacement Reactions
Mixed doubles in tennis, can the guy switch with a girl?
Example:
AgNO3(aq) + NaCl(s)  AgCl(s) + NaNO3(aq)

76. Double Replacement Reactions
Lead (II) Nitrate and Potassium Iodide 
Lead (II) Iodide and Potassium Nitrate
Pb(NO3)2 + 2 KI
PbI2 + 2
KNO3 

77. RB: p. 40 q
ODD only

78. BELL RINGER
Predict the following products and ID the reaction type: MgCl2 + NaOH 

79. Aluminum metal reacts with fluorine gas
Practice
Predict the product. Write and balance the following synthesis reaction equations.
Aluminum metal reacts with fluorine gas
Al(s) F2(g)  3 2
AlF3

80. Types of Reactions Lab

81. Types of Reactions Lab AND NO GARBAGE!
You need to make sure your tray has:
1 Test tube rack
4 test tubes
Box of matches
10 ml Graduated cylinder
Watch glass
Test tube tongs
Crucible tongs
Scoopula
Wood splint
Plastic spatula
Microspatula
AND NO
GARBAGE!

82. Mole Calculations

84. For the Scan-Tron p. 53+54 1 – 45 2 – 46 3 – 47 4 – 48 5 – 49 6 – 50
7 – 51
8– 52
9– 53
10– 54
11– 55
12– 56
13– 57
14 – 58
15 – 59
16 – 60
17 – 61
18 – 62
19 – 63
20 – 64
21 – 65
22 – 66
23 – 67
24 – 68
25 – 69
26 – 70
27 – 71

85. BELL RINGER
Write and balance the following: Magnesium and oxygen react to form magnesium oxide.

86. HW Quiz Decomposition of Aluminum oxide Synthesis of sulfur trioxide
Combustion of Methane (CH4)
Sodium bromide and silver nitrate form sodium nitrate and silver bromide.
Balance the following:
C6H12O6  C2H5OH + CO2

87. Are you smarter than a 5th Grader ….
Lila decided to make more baked goods for the bake sale. She used 1/8 lb less flour to make bread than to make cookies. She used ¼ lb more flour to make cookies than to make brownies. If she used ½ lb of flour to make the bread, how much flour did she use to make the brownies?

88. Stoichiometry
A way to predict how many products can be made or how many reactants would be needed. You need to get the equation written correctly and balanced properly.
2H2 + O2  2H2O
For example:
You would need 2 moles of Hydrogen to make 2 moles of water
1 mole of oxygen would make 2 moles of water
If you made 6 moles of water, how much hydrogen would you need?
6 moles
What would the mass of that be?
 12 grams
If you had 12 moles of oxygen and 2 moles of hydrogen, how much water could you make?
2 moles of water

89. Stoichiometry 2 3 AuCl3  Au + Cl2
How many moles of gold can be liberated from the decomposition of 5.2 moles of gold (III) chloride?
AuCl3  Au Cl2 2 3
Mass
GFM
Moles ?
5.20 mol
5.20 mol
Setup mole ratio

90. Stoichiometry 2 3 AuCl3  Au + Cl2
How many grams of Chlorine can be liberated from the decomposition of 64.0g of gold(III) chloride?
AuCl3  Au Cl2 2 3
Mass
GFM
Moles
64.0g ?
22.5 g
303.5g/mol
71.0 g/mol
.211 mol
.317 mol
Setup mole ratio

91. Stoichiometry 2 3 AuCl3  Au + Cl2
How many grams of gold can be liberated from the decomposition of 0.50 moles of gold (III) chloride?
AuCl3  Au Cl2 2 3
Mass
GFM
Moles ?
98.5 g
197.0 g/mol
0.50 mol
0.50 mol
Setup mole ratio

92. How many grams is 1.25 moles of Sodium hydroxide
BELL RINGER
How many grams is 1.25 moles of Sodium hydroxide
GFM = 40 Moles = 1.25 x 40 = 50 g

93. BELL RINGER
Gold (III) Chloride breaks into its component elements. Write the balanced equation for this reaction.

94. BELL RINGER
Al + O2  Al2O3 What is the total number of moles of O2 that must react completely with 8.0 moles of Al in order to form Al2O3?

95. Don’t panic – Balance the equation
Stoichiometry
How many moles of carbon dioxide are needed to produce moles of glucose in the following reaction:
CO H2O  C6H12O O2 6
Mass
GFM
Moles
2.00mol ?
0.333 mol
Setup mole ratio
Don’t panic – Balance the equation

96. Stoichiometry
What mass of carbon dioxide is needed to react with 54.0g of water in the following reaction:
CO H2O  C6H12O O2 6
Mass
GFM
Moles ?
54.0g
132.0 g
44.0 g/ mol
18.0g/mol
3.00 mol
3.00 mol
Setup mole ratio
Don’t panic – Balance the equation
Must convert to moles – NEVER grams

97. BELL RINGER
KClO3(s)  KCl(s) + O2(g) If you have 20.0 g of potassium chlorate, how many moles of oxygen could you make?

98. Practice Predict the products. Balance the equation
1. HCl(aq) + AgNO3(aq) 
HNO3(aq) + AgCl(s)
2. CaCl2(aq) + Na3PO4(aq)  3 2 6
NaCl(aq) + Ca3(PO4)2(s)
3. Pb(NO3)2(aq) + BaCl2(aq) 
PbCl2(s) + Ba(NO3)2(aq)
4. FeCl3(aq) + NaOH(aq)  3
Fe(OH)3(s) + NaCl(aq) 3
5. H2SO4(aq) + NaOH(aq)  2 2
HOH + Na2SO4(aq)
6. KOH(aq) + CuSO4(aq) 
K2SO4(aq) + Cu(OH)2(s) 2

100. BELL RINGER
Write the balanced equation for the decomposition of potassium chlorate.

102. BELL RINGER
If you wanted to make moles of hydrogen gas from the decomposition of water, how many moles of water would you need to start with?

103. Mixed Practice
State the type, predict the products, and balance the following reactions:
BaCl2 + H2SO4 
C6H12 + O2 
Zn + CuSO4 
Cs + Br2 
FeCO3 

104. To get Molecular Formula from Empirical Formula
Problem: You know a compound has an empirical formula of CN and a molecular mass of 52.0g. What is the molecular formula?
Find the mass of the empirical formula
C – N – 14 = 26
How many times does that mass divide into the molecular mass?
52 / 26 = 2
Multiply that number to each element in the empirical formula
C2N2

105. Determining Formulas from %
Hydrated Crystals
A student starts with 25.0 g of Barium Chloride Hydrate. The student performs the lab and has 21.4 g of anhydrous salt. What was the original formula of the hydrated crystal?
1. You already have g so you do not have to assume g.
2. Convert to moles
BaCl2  g/mol
Salt –
21.4 g
÷ g/mol
= mol
H2O –
3.6 g
÷ g/mol
= 0.20 mol

106. Determining Formulas from %
Hydrated Crystals
Percent to mass
Mass to moles
Divide by small
Multiply ‘til whole
3. Divide by small
Salt
 ÷ 0.103
= 1
BaCl2• ?H2O
H2O
 ÷
= 1.94
4. Multiply ‘til whole
Do Not need to here!
Just Round
BaCl2• 2H2O

107. GFM Practice 1. NaBr 6. C6H12O6 2. PbSO4 7. Fe3(PO4)2 3. Ca(OH)2
8. (NH4)2S
4. Na3PO4
9. Zn(C2H3O2)2
5. (NH4)2CO3
10. AgF

108. GFM Practice 1. NaBr 6. C6H12O6 2. PbSO4 7. Fe3(PO4)2 3. Ca(OH)2
102.9 g/mol
180.0 g/mol
2. PbSO4
7. Fe3(PO4)2
303.3 g/mol
357.4 g/mol
3. Ca(OH)2
8. (NH4)2S
74.1 g/mol
68.1 g/mol
4. Na3PO4
9. Zn(C2H3O2)2
164.0 g/mol
183.4 g/mol
5. (NH4)2CO3
10. AgF
126.9 g/mol
96.0 g/mol

109. Copper (II) sulfate●pentahydrate Sodium Hydrogen Carbonate
GFM
Whiteboard Review
Zinc
Copper (II) sulfate●pentahydrate
Sodium Hydrogen Carbonate
Sucrose
C12H22O11
Sodium Carbonate
Iron
Sodium Chloride
Water
Aluminum