Transcript AP CHEMISTRY - Auburn School District

AP CHEMISTRY
Chapter 3
© 2005 Mark S. Davis
Law of Conservation of
Mass
• Mass is neither created nor
destroyed in chemical reactions
– Lavoisier
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Chemical equations
• Tell you:
– What has
– What
– Ratio of
– Products, reactants
– Conditions
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Generally
• Reactants  Products
• Coefficients
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Symbols
•
•
•
•
•
•
(s)
(l)
(g)
(aq)

+
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Example
• Carbon is burned in air to form
carbon dioxide
•
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Example
• Carbon is burned in air to form
carbon monoxide
•
2
2
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Balancing equations
• Why?
– To show conservation of mass
– Keep proper amounts of reactants and
products
– Show proper ratios between products
and reactants
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Example
C 2H 6 + O2 
CO2 + H2O
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Patterns of reactivity
• Groups are similar in reactivity
• Alkali metals
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Types of reactions
•
•
•
•
•
Combustion
Synthesis (Combination)
Decomposition
Single Replacement
Double Replacement
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Combustion Reaction
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Combustion
• Occurs in air
•
•
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Combustion Reactions
• Fuel – Carbon compound
• Ignition source – flame
• Oxygen source
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Synthesis Reaction
• Reaction of two substances to form
one product
• Either elements or compounds react
to form one compound as product
• Generally:
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Example
Mg +
O2 
MgO
Sodium reacts with Chlorine
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Decomposition Reaction
• One compound breaks apart to form
two or more other elements or
compounds.
• Generally:
• Sodium azide
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Airbags
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Example
NaN3(s) 
Na(s) +
N2(g)
Sugar is decomposed to form
carbon and water
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Single Replacement
• Reaction of an element and a
compound to form two new
substances
• Generally:
• Zinc and Copper sulfate
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Example
Zn(s) + CuSO4(aq) 
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Solubility Rules
• In the book… table 4.1 p 111
• Also posted online.
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Double Replacement
• Two solutions react to form two or
more new substances
• Generally:
• Lead (II) nitrate and potassium
iodide
• Identify the solid, gas, liquid,
aqueous components
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Example
Pb(NO3)2(aq) + KI(aq)
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• http://dbhs.wvusd.k12.ca.us/webdoc
s/ChemTeamIndex.html
• http://dbhs.wvusd.k12.ca.us/webdoc
s/Equations/Equations.html
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Atomic Weights
• The weight of an atom of an element
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Average Atomic Mass
• Average mass of all the isotopes of
an element
– 98.5% C-12
– 1.5% C-13
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Formula Weight
• The sum of the masses of all the
atoms in a compound.
• Usually refers to
–
–
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Molecular Weight
• The weight of all the atoms in a
–
–
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The MOLE
• Quantity of a
substance
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Molar Mass
• The mass in grams of one mole of a
substance
–
–
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Avogadro’s Number
• The number of
particles in one
mole of a
compound
• 6.022 x 1023
particles in one
mole
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Conversions
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Empirical Formulas
• Simplest formula
• C6H12O6 can be reduced to
• Represents the
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Empirical Formulas
• Ethylene glycol, the substance used
in automobile antifreeze, is
composed of 38.7% C, 9.7% H, and
51.6% O by mass. Its molar mass is
62.1 g/mol. What is the empirical
formula? What is the molecular
formula?
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Empirical Formulas
• Caproic acid, which is responsible
for the foul odor of dirty socks, is
composed of C, H, O. Combustion
of 0.225 g of caproic acid produces
0.512 g CO2 and 0.209 g H2O.
What is the empirical formula of
caproic acid? If it has a molar mass
of 116 g/mol, what is the molecular
formula?
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Problem
• Determine the empirical formula
of a compound that has the
composition of 20.20 %
magnesium, 26.60 % sulfur,
53.20 % oxygen.
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Problem 2
• It was determined that a
compound was made from
43.66 % P and 56.34 % O, what
is the empirical formula?
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Molecular Formulas
• Represents the formula of the
actual molecule
• If the empirical formula is CH2O
and the molar mass is 120 amu,
what is the molecular formula?
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Early Stoichiometry
• Stoichiometry Steps for success
online
• Method of converting
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Limiting Reactants
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Theoretical Yield
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