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Chapter 12 Chemical Reactions•12-1. Phlogiston
•12-2. Oxygen
•12-3. The Mole
•12-4. Formula Units
•12-5. Exothermic and Endothermic Reactions
•12-6. Chemical Energy and Stability
•12-7. Activation Energy
•12-8. Liquid Fuels
•12-9. Gas Fuels
•12-10. Solid Fuels
•12-11. Temperature
•12-12. Other Factors
•12-13. Chemical Equilibrium
•12-14. Altering an Equilibrium
•12-15. Electrolysis
•12-16. Electrochemical Cells
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12-1. Phlogiston
Two early German chemists, Johann Becher and Georg Stahl, developed the phlogiston hypothesis.
Johann Becher 1635-1682)
Georg Stahl(1669-1734)
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The seventeenth century French chemist Antoine Lavoisier performed experiments that rejected the phlogiston hypothesis.
Lavoisier's experiments suggested that when tin is heated, the white powder formed results from the tin combining with a gas from the air.
The increase in mass of the powder over the tin was the mass of the gas.
Lavoisier revolutionized chemistry by basing his ideas on accurate measurements.
Antoine Lavoisier
(1743-1794)
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The English chemist Joseph Priestley discovered a
gas that Lavoisier later named oxygen
When oxygen combines
chemically with another
substance, the process
is called oxidation, and
the substance is said to
be oxidized.
Joseph Priestley(1733-1804)
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Fig. 12.4-5
Rust is caused by the reaction of oxygen with iron.A fire can be put out by cooling it with water or
depriving it of oxygen. Burning is the result of oxygen reacting with other materials.
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12.3 The Mole
The mole is a number, 6.02 x 1023. When you have a
mole of something you have 6.02 x 1023 of them. When
you have a mole of atoms or molecules you have enough
to see and weigh. The weight of a mole of one type of
atoms is the atomic weight from the periodic table in
grams. The mole allows you to count atoms by weighing.
For example, how many carbon atoms are there in 24
grams of carbon? From the periodic table each mole has
12 grams. So there are 2 moles or 2 x 6.02x1023 atoms of
carbon or 12.04x1023 carbon atoms.
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Fig. 12.6
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12.3 The Mole Figs. 12.7-8
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12.4 Formula Units
To find out how much a mole of molecules weigh you
just add up the atomic weights of the atoms in the
molecule.
How much does one mole of NaOH weigh?
Add the atomic weights of Na, O, and H you get 23 +
16 + 1 = 40 grams. How much does a mole of H2O
weigh?
Add 2 times 1 for H and 16 for O to get 18 grams.
How much does a mole of C3H8 weigh?
(3 x 12) + (8 x 1 ) = 36 + 8 = 44 grams.
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Fig. 12.9
C3H8 + 5O2 ���� 3CO2 + 4H2O
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12.5 Exothermic and Endothermic Reactions
•Chemical changes that give off energy are called exothermic reactions.
•Chemical changes that absorb energy are called endothermic reactions.
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Fig. 12.10-11
35/97 people died in 1937
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12.6 Chemical Energy and
Stability
The more energy needed to decompose a substance, the greater the chemical stability of the substance (with a few exceptions).
Chemical energy is electron potential
energy.
When electrons move to new locations
during an exothermic reaction, some of
their original potential energy is
liberated.
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Table 12.1
Histamine attacks
are greater when you
are hot. Cooling
down affected areas
can reduce allergy
symptoms.
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What Affects Chemical Reactions?
•Temperature•A 10oC rise in temperature approximately doubles the
speed of a chemical reaction occurring at or near room temperature.
•Concentration and Surface Area
•Catalysts (enzymes)•A catalyst is a substance that can change the rate of a chemical reaction without itself being permanently changed.
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What makes Switzerland unique?
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Activation Energy
Chemical Reactions must go over an energy
hill like a mountain (Swiss Alps).
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O-zone depletion from Antarctica
Depletion is measured by T.O.M.S.
“Total O-zone Mapping Spectrometer”
The below dark shaded are shows the amount of depletion around the Antarctica
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Use of Various Fuels
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Liquid Fuels
Petroleum, a mixture of various hydrocarbons, is the source of most liquid fuels.
Use a catalytic converter to convert the polluting exhaust gases of burned lead-free gasoline into harmless gases.
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Gas Fuels
Natural gas is largely methane, CH4.
Syngas
Coal can be gasified
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Hydroelectric Energy
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Solid Fuels
Types of solid fuels include coal, wood, and coke
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Solid Fuels
Acid rain from sulfur impurities in coal.
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Chemical EquilibriumChemical EquilibriumChemical EquilibriumChemical Equilibrium
In a chemical equilibrium, forward and reverse reactions
occur at the same rate; the
concentration of the reactants and products remain
constant. You can cause the
equilibrium to shift by adding or removing reactants or
products.
Below CO2 gas is in equilibrium with the water in
the soda.
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Electrolysis (Electroplating)Electrolysis (Electroplating)Electrolysis (Electroplating)Electrolysis (Electroplating)
Steel plated with tin prevents corrosion and is used in beverage containers. One key above has been plated with copper.
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More examples of
electroplating.
Electrolysis (Electroplating)Electrolysis (Electroplating)Electrolysis (Electroplating)Electrolysis (Electroplating)
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Types of Batteries
The Lead Storage
BatteryElectrochemical cells use oxidation-
reduction reactions
to produce electric current.
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Types of Batteries
The
Alkaline
Battery
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Types of
Batteries
The
Lithium
Battery
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Hydrogen gas is an excellent fuel produced by the electrolysis of water.
Hydrogen Fuel Cell
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Lecture Quiz 12
1. How many atoms are in a mole?
2. What is activation energy?
3. Give an example of an exothermic reaction?
4. What is probably the cheapest form of energy?
5. How much does one mole of H2O weigh?
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Lecture Quiz 12
1. How many atoms are in a mole? 6.02x10-23
2. What is activation energy? Energy needed to get over the energy hill or cause a reaction.
3. Give an example of an exothermic reaction? Burning wood
4. What is probably the cheapest form of energy? Hydroelectric
5. How much does one mole of H2O weigh? 18g
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Lecture Quiz 12
1. What is a catalytic converter?
2. Who did an experiment with tin and light?
3. What does exothermic and endothermic mean?
4. Who discovered oxygen?
5. How much does one mole of CO2
weigh?
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Lecture Quiz 12
1. What is a catalytic converter?Found on exhaust pipe and converts pollutants to harmless gases.
2. Who did an experiment with tin and light? Antoine Lavoisier
3. What does exothermic and endothermic mean? exothermic-gives off heat, endothermic-absorbs heat
4. Who discovered oxygen? Joseph Pieistley
5. How much does one mole of CO2weigh? 44 grams (12 for carbon and 2x16 for oxygen)
