A General Features of Physical and Chemical Changes A chemical change a chemical reaction converts one substance into another Chemical reactions involve Breaking bonds in the reactants ID: 790981
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5.1 Introduction to Chemical ReactionsA. General Features of Physical and Chemical Changes
A chemical change (a chemical reaction) converts one substance into another.
Chemical reactions involve:
Breaking bonds in the reactants (starting materials)
Forming new bonds in the products
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5.1 Introduction to Chemical ReactionsA. General Features of Physical and Chemical Changes
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5.1 Introduction to Chemical ReactionsB. Writing Chemical Equations
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5.1 Introduction to Chemical ReactionsB. Writing Chemical Equations
A chemical equation uses chemical formulas and othersymbols showing what reactants are the starting
materials in a reaction and what products are formed.
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5.1 Introduction to Chemical ReactionsB. Writing Chemical Equations
The law of conservation of mass states that atoms cannot be created or destroyed in a chemical reaction.
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5.2 Balancing Chemical Equations
HOW TO Balance a Chemical EquationExample
Write a balanced chemical equation forthe reaction of propane (C3H8) with oxygen (O2) to form carbon dioxide (CO2)and water (H2O).Step [1]
Write the equation with the correct formulas.
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5.2 Balancing Chemical Equations
Step [2]HOW TO Balance a Chemical Equation
Balance the equation with coefficients oneelement at a time.
Balance the C’s first:
Balance the H’s next:
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5.2 Balancing Chemical Equations
Step [2]HOW TO Balance a Chemical Equation
Balance the equation with coefficients oneelement at a time.
Finally, balance the O’s:
Slide9Balance the Equations9__H2 + __O2 __H2O__NO + __O2 __NO2__CH4 + __Cl2 __CH
2Cl2 + __HCl
Slide10Polyatomic Ions10__Ca3(PO4)2 + __H2SO4 __CaSO4 + __H3PO4
Slide11Balance the Equation11__Al + __H2SO4 __Al2(SO4)3 + __H2__Na2SO3 + __H3PO4
__H2SO3 + __Na
3PO4
Slide12Balance the Equation12__Mg + __HBr __MgBr2 + __H2__KClO3 __KCl + __O2__CH4 + __Cl2 __CCl4 + __HCl
Slide13Balance the Equation13__Al2O3 + __HCl __AlCl3 + __H2O__Al(OH)3 + __H2SO4 __Al2(SO4
)3 + __H2O
Slide14__Ni + __HCl __NiCl2 + __H2__PbS + __O2 __PbO + __SO2__H3PO4 + __Ca(OH)2 __Ca3(PO4
)2 + __H2
O
Slide15__H2SO4 + __NaOH __Na2SO4 + __H2O__CO + __O2 __CO2__S + __O2 + __H2
O __H2SO4
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5.3 Types of Reactions
The majority of chemical reactions fall into 6 categories:
combinationdecompositionsingle replacement
double replacementoxidation and reduction (Section 5.4)acid-base (Chapter 9)
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5.3 Types of ReactionsA. Combination and Decomposition
A combination reaction is the joining of two or more reactants to form a single product.
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5.3 Types of ReactionsA. Combination and Decomposition
A decomposition reaction is the conversion of a single reactant to two or more products.
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5.3 Types of ReactionsB. Replacement Reactions
A single replacement reaction is a reaction in which one element replaces another element in a compound to form a different compound and element as products.
Slide20205.3 Types of ReactionsB. Replacement Reactions2 NaCl + Br2 Fe + CaSO4
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5.3 Types of ReactionsB. Replacement Reactions
A double replacement reaction is a reaction in which two compounds exchange “parts”–atoms or ions—to form two new compounds.
Slide22225.3 Types of ReactionsB. Replacement ReactionsAgNO3 + NaClHCl + NaOH
Slide23Combination, Decomposition, Single Displacement or Double Displacement?23Ni(NO3)2 + Mg Ni + Mg(NO3)22 KI + Sn(NO3)2 SnI2 + 2 KNO3
2 HgO
2 Hg + O2
Slide2424Mg + 2 ZnCl MgCl2 + 2 ZnH2C=CH2 + HBr CH3CH2BrKCN + HCl
KCl + HCN
Slide25256 Na + AlSO4 3 NaSO4 + 2 AlKNO3 + HBr KBr + HNO3
Slide26Predicting Reactions26Combination: N2 + ____ Mg3N2Decomposition: 2 SO3 2SO2 + ______Single Replacement: 2 Ag + CuBr2 ______ + ______Double Replacement: KOH + HI ______ + _______
Slide2727Comb: 2 Na + Cl2 Decomp: 2 NI Single: Cl2 + Ki Double: NaOH + HBr
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5.4 Oxidation and ReductionA. General Features
Oxidation is the loss of electrons from an atom.
Reduction
is the gain of electrons by an atom.
Both processes occur together in a single reaction called an oxidation−reduction or redox reaction.
A
redox
reaction involves the
transfer of electrons
from one element to another.
A redox reaction always has two components, one that is oxidized and one that is reduced.
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5.4 Oxidation and ReductionA. General Features
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5.4 Oxidation and ReductionA. General Features
Oxidation half reaction:
Each of these processes can be written as an individual half reaction
:Zn + Cu2+
Zn
2+
+ Cu
Reduction
half reaction:
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5.4 Oxidation and ReductionA. General Features
Zn + Cu2+
Zn
2+ + Cu
A compound that is reduced while causing anothercompound to be oxidized is called an oxidizing agent.
Cu
2+
acts as an
oxidizing agent
because it causes
Zn to lose electrons and become
oxidized
.
oxidized
reduced
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5.4 Oxidation and ReductionA. General Features
Zn + Cu2+
Zn
2+ + Cu
Zn acts as a reducing agent because it causes Cu2+ to gain electrons and become reduced.
A compound that is
oxidized
while causing another
compound to be
reduced
is called a
reducing agent
.
oxidized
reduced
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5.4 Oxidation and ReductionA. General Features
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5.4 Oxidation and Reduction
B. Examples of Oxidation–Reduction Reactions
Iron Rusting
4 Fe(s) + 3 O2(g)
2 Fe2O3(s)
Fe
3+
O
2–
neutral Fe
neutral O
Fe loses e
–
and is oxidized.
O gains e
–
and is reduced.
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5.4 Oxidation and ReductionB. Examples of Oxidation–Reduction Reactions
Zn + 2 MnO2
ZnO + Mn
2O3
Slide36Zn + 2H+ Zn2+ + H2Fe3+ + Al Al3+ + Fe
Slide37I- + Br2 I2 + Br-AgBr Ag + Br2
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5.4 Oxidation and ReductionB. Examples of Oxidation–Reduction Reactions
Oxidation results in the:
Reduction results in the:
Gain of oxygen atoms
Loss of hydrogen atoms
Loss
of
oxygen
atoms
Gain
of
hydrogen
atoms
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5.5 The Mole and Avogadro’s Number
A mole is a quantity that contains 6.02 x 1023 items.
1 mole of C
atoms = 6.02 x 1023 C atoms
1 mole of H2O molecules = 6.02 x 1023 H2O molecules
1 mole of Vitamin C
molecules
= 6.02 x 10
23
Vitamin C
molecules
The number 6.02 x 10
23
is
Avogadro’
s number
.
1.3×10
23
kg
Titan
, largest moon of Saturn
1.5×10
23
kg
Ganymede
, largest moon of Jupiter
3.3×10
23
kg
Mercury
6.4×10
23
kg
Mars
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How many items do 1 mol of the following contain:
BaseballsBicycles
CheeriosCH4 molecules
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5.5 The Mole and Avogadro’s Number
It can be used as a conversion factor to relate thenumber of moles
of a substance to the number ofatoms or molecules:
1 mol6.02 x 1023 atoms
or
6.02 x 10
23
atoms
1 mol
1 mol
6.02 x 10
23
molecules
or
6.02 x 10
23
molecules
1 mol
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5.5 The Mole and Avogadro’s Number
Sample Problem 5.5
How many molecules are contained in 5.0 moles of carbon dioxide (CO2)?Step [1]
Identify the original quantity and the desired quantity.
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5.5 The Mole and Avogadro’s Number
Step [3]
Set up and solve the problem.Step [2]
Write out the conversion factors.
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How many C atoms are there in the following:
2.0 mol6.0 mol0.5 mol25.0 mol
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How many molecules are contained in each of the following number of moles
2.5mol of penicillin0.25 mol of NH30.4 mol of Sugar55.3 mol of Acetaminophen
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5.6 Mass to Mole Conversions
The formula weight is the sum of the atomic weights of all the atoms in a compound, reported in atomic mass units (amu).
HOW TO Calculate the Formula Weight of a CompoundExample
Calculate the formula weight for FeSO4.Step [1]
Write the correct formula and determinethe number of atoms of each element fromthe subscripts.
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5.6 Mass to Mole Conversions
HOW TO Calculate the Formula Weight of a CompoundStep [2]
Multiply the number of atoms of each element by the atomic weight and addthe results.
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5.6 Mass to Mole ConversionsA. Molar Mass
The molar mass is the mass of one mole of any substance, reported in grams per mole (g/mol).
The value of the molar mass of a compound in grams equals the value of its formula weight in amu.
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5.6 Mass to Mole ConversionsB. Relating Grams to Moles
The molar mass relates the number of moles to the number of
grams of a substance.
In this way, molar mass can be used as a conversion factor.
The molar mass of H2O is 18.0 g/mol, the conversion factor can be written:
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5.6 Mass to Mole ConversionsB. Relating Grams to Moles
Sample Problem 5.9
How many moles are present in 100. g of aspirin (C9H8O4)?Step [1]
Calculate the molar mass.
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5.6 Mass to Mole ConversionsB. Relating Grams to Moles
Step [2]
Write out the conversion factors.
The conversion factor is the molar mass, and it can be written in two ways.
Choose the one that places the unwanted unit, grams, in the denominator so that the units cancel:
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5.6 Mass to Mole ConversionsB. Relating Grams to Moles
Step [3]
Set up and solve the problem.
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How many moles are contained in the following:
100 g NaCl
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How many moles are contained in the following:
0.25g Aspirin(C9H8O4)
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How many moles are contained in the following:
25.5g CH4
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How many moles are contained in the following:
25g of H2O
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5.6 Mass to Mole ConversionsC. Relating Grams to Number of Atoms or Molecules
We can also use the molar mass to show the relationship between grams and number of
molecules (or atoms).
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5.6 Mass to Mole ConversionsC. Relating Grams to Number of Atoms or Molecules
Sample Problem 5.10
How many molecules are in a 325-mg tablet of aspirin (C9H8O4)?Step [1]
Find the molar mass
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5.6 Mass to Mole ConversionsC. Relating Grams to Number of Atoms or Molecules
Step [2]
Write out the conversion factors.
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5.6 Mass to Mole ConversionsC. Relating Grams to Number of Atoms or Molecules
Step [3]
Set up and solve the problem.
Slide61How many molecules are present in a 500mg tablet of penicillin (C16H18N2O4S)61
Slide62How many molecules are present in a 500mg tablet of penicillin (C16H18N2O4S)62
Slide63How many molecules are present in a 750mg of Mescaline (Hallucinogenic from peyote) (C11H17NO3)63
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5.7 Mole Calculations in Chemical Equations
A balanced chemical equation also tell us:
The number of moles of each reactant that combineThe number of moles of each product formed
1 N2(g
)+
1 O
2
(
g
)
2 NO(
g
)
(The coefficient
“
1
”
has been written for emphasis.)
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5.7 Mole Calculations in Chemical Equations
Coefficients are used to form mole ratios, which canserve as
conversion factors.
N2(g)
+ O2(g)
2 NO(
g
)
Mole ratios:
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5.7 Mole Calculations in Chemical Equations
Sample Problem 5.11
Using the balanced chemical equation, how many moles of CO are produced from 3.5 molesof C2H6?Step [1]
Identify the original and desired quantities.
2 C2H6(g) + 5 O2(g)
4 CO(
g
) + 6 H
2
O(
g
)
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5.7 Mole Calculations in Chemical Equations
Step [2]
Write out the conversion factors.Step [3]
Set up and solve the problem.
2 C2H6(g) + 5 O2(g)
4 CO(
g
) + 6 H
2
O(
g
)
Slide68Complete the following conversionsHow many mol of NO are formed from 3.3 mol of N2How many mol of NO are formed from 0.5mol of O2How many moles of O2 are needed to completely react with 1.2 mol of N268
N
2(g)
+
O2(g)
2 NO(g)
Slide69How many mol of NO are formed from 3.3 mol of N2How many mol of NO are formed from 0.5mol of O269
N
2(g)
+
O2(g)
2 NO(g)
Slide70How many moles of O2 are needed to completely react with 1.2 mol of N270
N
2(g)
+
O2(g)
2 NO(g)
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5.8 Mass Calculations in Chemical Equations
HOW TO Convert Moles of Reactant to Grams of ProductExample
Using the balanced equation, how manygrams of O3 are formed from 9.0 mol of O2.
3 O2(g)
2 O3(g)
sunlight
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5.8 Mass Calculations in Chemical Equations
Step [1]
Convert the number of moles of reactantto the number of moles of product usinga mole–mole conversion factor.HOW TO Convert Moles of Reactant to Grams of Product
3 O2(g)
2 O3(g)
sunlight
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5.8 Mass Calculations in Chemical Equations
HOW TO Convert Moles of Reactant to Grams of ProductStep [2]
Convert the number of moles of productto the number of grams of product using the product’s molar mass.
Slide7474
5.8 Mass Calculations in Chemical Equations
HOW TO Convert Moles of Reactant to Grams of Product
Set up and solve the conversion.
3 O2(g)
2 O3(g)
sunlight
Slide75C6H12O6 2 C2H6O + 2CO2How many g of ethanol are formed from 0.55 mol of glucoseHow many g of CO2 are formed from 0.25 mol of glucoseHow many g of glucose are needed to form 1mol of ethanol75 (ethanol) (glucose)
Slide76How many g of ethanol are formed from 0.55 mol of glucose76
C6
H12O6 2 C2H6O + 2CO2
Slide77How many g of CO2 are formed from 0.25 mol of glucose77
C
6H12O6 2 C2H6O + 2CO2
Slide78How many g of ethanol would be formed if 0.55 mols of glucose is used78
C6
H12O6 2 C2H6O + 2CO2
Slide7979
5.8 Mass Calculations in Chemical Equations
HOW TO Convert Grams of Reactant to Grams of ProductExample
Ethanol (C2H6O) is synthesized by reacting ethylene (C2H4) with water.How many grams of ethanol are formed from 14 g of ethylene?
C2H4 + H2O
C2H6O
Slide8080
5.8 Mass Calculations in Chemical Equations
HOW TO Convert Grams of Reactant to Grams of Product
C2H4 + H2O
C2H6O
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5.8 Mass Calculations in Chemical Equations
HOW TO Convert Grams of Reactant to Grams of Product
C2H4 + H2O
C2H6O
Slide8282
5.8 Mass Calculations in Chemical Equations
HOW TO Convert Grams of Reactant to Grams of Product
C2H4 + H2O
C2H6O
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Slide841) How many molecules of CO is produced?2) How many g of C2H6 are needed to react with all of O23) How many g of H2O are produced when 15g of O2 is used.84
2 C
2H6(g) + 5 O2(g)
4 CO(g) + 6 H2O(g)
Slide852 C
2H6(g
) + 5 O2(g)
4 CO(g) + 6 H2O(g)How many molecules of CO is produced?
Slide862 C
2H6(g
) + 5 O2(g)
4 CO(g) + 6 H2O(g)How many g of C2H6 are needed to react with all of O2
Slide872 C
2H6(g
) + 5 O2(g)
4 CO(g) + 6 H2O(g)How many g of H2O are produced when 15g of O2 is used.
Slide882 NO + O2 2 NO2How many g of NO2 are formed from 20g of NO?
Slide892 NO + O2 2 NO2How many g of NO are needed to make 30g of NO2?
Slide902 CH4O + 3 O2 2 CO2 + 4 H2OHow many grams of CO2 are formed from 50g CH4O?
Slide9191
5.9 Percent Yield
The theoretical yield is the amount of product expected from a given amount of reactant based on the coefficients in the balanced chemical equation.
The percent yield is the amount of product isolated from a reaction.
Usually, however, the amount of product formed is less than the maximum amount of product predicted.
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5.9 Percent Yield
Sample Problem 5.14
If the reaction of ethylene with water to form ethanol has a calculated theoretical yield of 23 g of ethanol, what is the percent yield if only 15 g of ethanol are actually formed?
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5.10 Limiting Reactants
The limiting reactant is the reactant that is completely used up in a reaction.
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5.10 Limiting ReactantA. Determining the Limiting Reactant
Analyze the two possible outcomes:
If the amount present of the second reactantis
less than what is needed, the secondreactant is the limiting reagent.
If the amount present of the second reactant isgreater than what is needed, the secondreactant is in excess.
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5.10 Limiting ReactantC. Determining the Limiting Reactant Using the Number of Grams
Sample Problem 5.20
Using the balanced equation, determine the limitingreactant when 10.0 g of N2 (MM = 28.02 g/mol) reactwith 10.0 g of O2 (MM = 32.00 g/mol).
N2(g) + O2(g) 2 NO(g)
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5.10 Limiting ReactantC. Determining the Limiting Reactant Using the Number of Grams
Sample Problem 5.20
[1] Convert the number of grams of each reactant into moles using the molar masses.
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5.10 Limiting ReactantC. Determining the Limiting Reactant Using the Number of Grams
Sample Problem 5.20
[2] Determine the limiting reactant by choosing N2 as the original quantity and converting to mol O2.
1 mol O21 mol N2
0.357 mol N2 x
= 0.357 mol O
2
mole–mole
Conversion factor
The amount of O
2
we started with (0.313 mol) is
less than the amount we would need (0.357 mol) so
O
2
is the limiting reagent
.
Slide98N2(g) + O2(g) NO(g)Determine the limiting reactant under the following conditions:1) 12.5g N2 and 15.0g O22) 14.0g N2 and 13.0g O298
Slide9912.5g N2 and 15.0g O2N2(g) + O2(g) NO(g)
Slide100N2(g) + O2(g) NO(g)14.0g N2 and 13.0g O2
Slide101101Balance/Rxn Type/ REDOXNi + HCl NiCl2 + H2CH4 + Cl2 CCl4 + HClKClO3 KCl + O2
Al2O3
+ HCl AlCl3 + H2O
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Slide103103
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Slide105105Given the following reaction:C12H22O11 + H2O C2H6O + CO2 (sucrose) (ethanol) Balance the equationDetermine the molecular weight of sucroseHow many mols of Ethanol would be produced from 2
mols of sucrose?
How many g of ethanol would be produced from 17.1 g sucrose?
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