Using Chemical Formulas
7-3
Beaker Breaker
1. Name the following compounds:
CaCl2 = ____________
P3O6 = _____________
FeCl2 =______________
H2SO4 =______________
Formula Masses
• sum of the average atomic masses of all the atoms
represented in a formula
• (can be of a molecule, formula unit or ion)
• Formula mass of H2O:
• 2 (ave. atomic mass of H) +1(ave. at. mass of O)
• = 2(1.01 amu) + 1(16.00 amu)
• = 2.02 amu + 16.00 amu
• = 18.02 amu
Calculate the formula mass of
the following:
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sulfuric acid
calcium nitrate
phosphate ion
magnesium chloride
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sulfuric acid
98.09 amu H2SO4
calcium nitrate
164.10 amu Ca(NO3)2
phosphate ion
94.97 amu PO43magnesium chloride
95.21 amu MgCl2
Molar Masses
• sum of the masses of the elements present
in a mole of the molecules or formula units
that make up a compound
• Molar mass of water, H2O:
• 1 mole H2O = 2 mol H + 1 mol O
• 2 mol H x 1.01 g H =
2.02 g H
1 mol H
• 1 mol O x 16.00 g =
16.00 g O
1 mol O
18.02 g
• Molar mass of water = 18.02 g/mol
What is the molar mass of…
• aluminum sulfide
• sodium nitrate
• barium hydroxide
What is the molar mass of…
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aluminum sulfide
Al2S3 150.17 g/mol
sodium nitrate
NaNO3 85.00 g/mol
barium hydroxide
Ba(OH)2 171.35 g/mol
Beaker Breaker
1. Name the following the compounds:
CaBr2 =_______________
H3PO3 =_______________
C3I7 =_________________
CuCl3 = _______________
Gram-Mole Conversions
Using Molar Mass as a conversion
factor between “moles” ↔ “mass”
• What is the mass, in grams, of 0.50000 moles
of barium hydroxide?
• Given: 0.500000 mol Ba(OH)2
• Find: g Ba(OH)2
• Know: 1 mol Ba(OH)2 =171.35 g Ba(OH)2
• 0.500000 mol Ba(OH)2 x 171.35 g Ba(OH)2
1 mole Ba(OH)2
• = 85.675 g Ba(OH)2
How many moles are in 6.60 g
of ammonium sulfate?
• Given: 6.60g (NH4)2SO4
• Find: 0.0499 mol (NH4)2SO4
• Know: 1 mol(NH4)2SO4 = 132.17 g (NH4)2SO4
• (NH4)2SO4 = 2(N) + 8(H) + 1(S) + 4(O)
• =
2(14.01) + 8(1.01) + 1(32.07) + 4(16.00)
•
132.17 g/mol
• 6.60g (NH4)2SO4 x 1 mol(NH4)2SO4
132.17 g (NH4)2SO4
• = 0.0499 mol (NH4)2SO4
(4.99 x 10-2mol)
Gram-Mole Conversions
Remember….
1 mole = 6.02 x 1023 “things”
• How many molecules are in 50.0 g of water?
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Given: 50.0 g H2O
Find: molecules H2O
Know: 1 mol H2O = 18.02g
1 mol H2O = 6.02 x 1023 molecules H2O
50.0 g H2O x 1 mol H2O x 6.02 x 1023 molecules
18.02 g H2O
1 mol H2O
• = 1.67 x 1024 molecules H2O
White Board Practice with Partners
How many moles of compound are there in the
following
a. 6.60g (NH4)2SO4
b. 4,500g Ca(OH)2
Answers
• A. 0.0500mol
• B. 61mol
White Board Practice with Partners
• How many molecules are there in the
following:
a. 25.0g H2SO4
b. 125g of C12H22O11
Answers
• A. 1.53 x1023 molecules
• B. 2.20 x1023 molecules
Beaker Breaker
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1.
2.
3.
4.
Write the formulas of the following
compounds
Nitric Acid =___________
Hydroiodic acid =____________
Magnesium Fluoride =____________
Tetracarbon nonahydride =__________
Percentage Composition
• % = part x 100
whole
• percentage by mass of each element in a
cmpd
Find the % copper in copper(I) sulfide
• % Cu = part Cu
x 100
whole Cu2S
• % Cu = mass of Cu in 1 mole of Cu2S x 100
mass of 1 mol of Cu2S
Or...% Cu= mass of Cu in 1 mole of Cu2S x 100
molar mass of Cu2S
• Cu2S = 159.17 g/mol (molar mass..on bottom)
• 1 mol Cu2S, there are 2 mol Cu = 127.10 g Cu
(top term)
Know:
Find the % copper in
copper(I) sulfide
• % Cu = mass of Cu in 1 mole of Cu2S x 100
mass of 1 mol of Cu2S
• 1 mol of Cu2S = 159.17 g Cu2S
• 1 mol of Cu2S= 2mol Cu = 2(63.546g)= 127.10g
• = 127.10 g Cu
x 100
159.17 g Cu2S
• = 79.852% Cu in Cu2S
What is the percent carbon in
ammonium carbonate?
Know: (NH4)2CO3
•
% C = grams of C in 1 mol (NH4)2CO3 x 100
molar mass of (NH4)2CO3
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1 mol (NH4)2CO3 = 1 mol C = 12.01 g C
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1 mol (NH4)2CO3 = 96.11 g (NH4)2CO3
12.01 g C x 100
96.11 g
• = 12.50% C
• =
Beaker Breaker
1. Phosphoric acid can be used in
orthodontics to roughen the surface of
teeth before the placement of braces.
Write the chemical formula for phosphoric
acid.
2. Explain your method used to arrive to that
answer.
a. NH41+
Ammonium
b.ClO3Chlorate
c. OHHydroxide
d.SO42Sulfate
e. NO3Nitrate
f.CO32Carbonate
g. PO43Phosphate
h. CH3COOAcetate
i. HCO3Bicarbonate
j. CrO42Chromate
Homework Check
Pg 236 #25
Mix Review Challenge
Write the name or formula of the following:
1. MgSO3 =______________
2. Sodium Hydroxide = __________
3. Nickel (II) Fluoride =___________
4. P2H3 =__________
Answers
1.
2.
3.
4.
Magnesium Sulfite
NaOH
NiF2
Diphosphorus Trihydride
Mix Review Challenge
• Write the name or formula of the following:
5. Sulfurous acid =___________
6. Copper (II) Chloride =_________
7. AlPO4 =____________
8. TetraSulfur Heptoxide =__________
Answers
5. H2SO3
6. CuCl2
7. Aluminum Phosphate
8. S4O7