1 chapter 4 recycling and chemical mathematics. 2 nature’s recycling – the carbon cycle
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Chapter 4Chapter 4
Recycling and Chemical MathematicsRecycling and Chemical Mathematics
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Nature’s Recycling –The carbon cycle
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Chemical Equations
Chemical reaction: the reorganization of the atoms in one or more substances to form a different substance(s).
A chemical equation for respiration:
C6H12O6(s) + 6O2(g) → 6CO2(g) + 6H2O(l)
What does this equation mean?What does this equation mean?
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What does this equation mean?What does this equation mean?
C6H12O6(s) + 6O2(g) → 6CO2(g) + 6H2O(l)
“One molecule of glucose solid reacts with six molecules of oxygen gas to give (or produce) six molecules of carbon dioxide gas and six molecules of water.”
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Accounting for atoms in the process of respiration
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Example:Example: Recognizing Balanced Equations
Is the following equation balanced?
CaCl2 + 2Na3PO4 → Ca3(PO4)2 + 3NaCl
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Solution:Solution: Recognizing Balanced Equations
This is the balanced chemical equation.
33CaCl2 + 22Na3PO4 → Ca3(PO4)2 + 66NaCl
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Producing Aluminum via the Hall-Heroult Process
2Al2O3(l) + 3C(s) → 4Al(l) + 3CO2(g)
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Example:Example: Atomic Masses
The mass of an atom is the weighted average of its naturally-occurring isotopes.Gallium has 2 isotopes,
60.10% 69Ga (= 68.93 amu) and
39.90% 71Ga (= 70.92 amu).
What is the average atomic massaverage atomic mass of Ga?
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Solution:Solution: Atomic Masses
60.10% 69Ga (= 68.93 amu) and
39.90% 71Ga (= 70.92 amu).
What is the average atomic massaverage atomic mass of Ga?
(0.6010 x 68.93) + (0.3990 x 70.92) = contribution of 69Ga isotope contribution of 71Ga isotope
69.72 amu69.72 amu
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Formula Masses
The sum of the atomic masses of all the atoms in the formula.
H2O = 2 x 1.008 + 1 x 16.00 = 18.02 amu hydrogen oxygen
Fe(OH)3 = 1 x 55.847 + 3 x (16.00 + 1.008) = 106.87 amu iron oxygen hydrogen
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Avogadro’s Number
1 mol of anything = 6.02 x 1023 things 1 mol of C atoms = 6.02 x 1023 C atoms 1 mol of Al atoms = 6.02 x 1023 Al atoms
1 mol of Al2O3 = 6.02 x 1023 Al2O3 formula units 1 mol of frosted flakes =
6.02 x 1023 frosted flakes (Yum!)(Yum!)
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Conversions: Moles to Grams
How many grams of Al2O3 are in 31.27 moles of Al2O3?
= 3188 g Al= 3188 g Al22OO33
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3232 O Almol 1
O Alg 101.96 x O Almol 31.27
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Conversions: Grams to Moles
How many moles of (NH4)2Cr2O7 are in 586.2 grams of (NH4)2Cr2O7?
= 2.326 moles of NH= 2.326 moles of NH44CrCr22OO77
7224
72247224 OCr)(NH g 06252
OCr)(NH mol 1 x OCr)(NH g 586.2
.
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Using Equations for Stoichiometric Calculations
How many moles of iron can be formed from 2.8 moles of iron(III) oxide, Fe2O3?
Fe2O3 + 2Al → 2Fe + Al2O3
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Solution:Solution: Using Equations for Stoichiometric Calculations
How many moles of iron can be formed from 2.8 moles of iron(III) oxide, Fe2O3?
Fe2O3 + 2Al → 2Fe + Al2O3
= 5.6 moles Fe= 5.6 moles Fe
3232 OFe mol 1
Fe mol 2 x OFe mol 2.8
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Using Equations for Stoichiometric Calculations
How many grams of Al2O3 can be formed from 1162 grams of Fe2O3?
Fe2O3 + 2Al → 2Fe + Al2O3
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Using Equations for Stoichiometric Calculations
How many grams of Al2O3 can be formed from 1162 grams of Fe2O3?
Fe2O3 + 2Al → 2Fe + Al2O3
StrategyStrategy
g Fe2O3 → mol Fe2O3 → mol Al2O3 → g Al2O3
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Solution:Solution: Using Equations for Stoichiometric Calculations
How many grams of Al2O3 can be formed from 1162 grams of Fe2O3?
g Fe2O3 → mol Fe2O3 → mol Al2O3 → g Al2O3
= 741.8 g Al= 741.8 g Al22OO33
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3232 O Almol 1
O Alg 101.96 x
OFe mol 1
O Almol 1 x
OFe g 159.7
OFe mol 1 x OFe g 1162
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Using Equations for Stoichiometric Calculations
How many grams of CO2 can be formed from 80.7 grams of C6H12O6 in respiration? Assume excess oxygen.
C6H12O6 + 6O2 → 6CO2 + 6H2O
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Using Equations for Stoichiometric Calculations
How many grams of CO2 can be formed from 80.7 grams of C6H12O6 in respiration? Assume excess oxygen.
C6H12O6 + 6O2 → 6CO2 + 6H2O
StrategyStrategy
g C6H12O6 → mol C6H12O6 → mol CO2 → g CO2
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Solution:Solution: Using Equations for Stoichiometric Calculations
How many grams of Al2O3 can be formed from 1162 grams of Fe2O3?
g C6H12O6 → mol C6H12O6 → mol CO2 → g CO2
= 118 g CO= 118 g CO22
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2
6126
2
6126
61266126 CO mol 1
CO g 44.01 x
OHC mol 1
CO mol 6 x
OHC g 180.2
OHC mol 1 x OHC g 80.7
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Common Polymers and Their Monomers
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