1

Chapter 6

Chemical Reactions Classification and Mass Relationship

2

In a physical change, The identity and composition of the

substance do not change. The state can change or the material can

be torn into smaller pieces.

In a chemical change, New substances form with different

compositions and properties. A chemical reaction takes place.

Physical and Chemical Change

3

Physical and Chemical Change

4

Some Examples of Chemical and Physical Changes

5

Classify each of the following as a

1) physical change or 2) chemical change

A. ____ Burning a candle.

B. ____ Ice melting on the street.

C. ____ Toasting a marshmallow.

D. ____ Cutting a pizza.

E. ____ Polishing a silver bowl.

Learning Check

6

Classify each of the following as a

1) physical change or 2) chemical change

A. 2 Burning a candle.

B. 1 Ice melting on the street.

C. 2 Toasting a marshmallow.

D. 1 Cutting a pizza.

E. 2 Polishing a silver bowl.

Solution

7

Chemical Reaction In a chemical

reaction, a chemical change produces one or more new substances.

During a reaction, old bonds are broken and new bonds are formed.

8

In a chemical reaction, atoms in the reactants are rearranged to form one or more different substances.

In this reaction, Fe and O2 react to form rust (Fe2O3).

4Fe + 3O2 2Fe2O3

Chemical Reaction

9

A chemical equation Shows the chemical formulas of the reactants to the

left of an arrow and the products on the right. Reactants ProductsMgO + C CO + Mg

Can be read in words. “Magnesium oxide reacts with carbon to form carbon monoxide and magnesium.”

Writing a Chemical Equation

10

Symbols Used in Equations

Symbols used in equations show the states of the reactants and products and the reaction conditions.

11

4 NH3 + 5 O2 4 NO + 6 H2O

Four molecules of NH3 react with five molecules of O2 to produce four molecules of NO and six molecules of H2O.

or

Four moles of NH3 react with 5 moles of O2 to produce four moles of NO and six moles of H2O.

Quantities in A Chemical Reaction

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In any ordinary chemical reaction, matter is not created nor destroyed.

+ + H2 + Cl2 2 HCl=

Total Mass2(1.0) + 2(35.5) 2(36.5)73.0 g = 73.0 g

Law of Conservation of Mass

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6.2 Balancing a Chemical Equation

A chemical equation is balanced when there are the same numbers of each type of atom on both sides of the equation.

Al + S Al2S3 Not Balanced

2Al + 3S Al2S3 Balanced

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To balance an equation, place coefficients in front of the appropriate formulas. 4 NH3 + 5 O2 4 NO + 6 H2O

Check the balance by counting the atoms of each element in the reactants and the products.

4 N (4 x 1N) = 4 N (4 x 1N)12 H (4 x 3H) = 12 H (6 x 2H)10 O (5 x 2O) = 10 O (4O + 6O)

Using Coefficients to Balance

15

Check the balance of atoms in the following: Fe3O4 + 4 H2 3 Fe + 4 H2O

A. Number of H atoms in products.

1) 2 2) 4 3) 8

B. Number of O atoms in reactants.

1) 2 2) 4 3) 8

C. Number of Fe atoms in reactants.

1) 1 2) 3 3) 4

Learning Check

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Fe3O4 + 4 H2 3 Fe + 4 H2O

A. Number of H atoms in products.

3) 8 (4H2O)

B. Number of O atoms in reactants.

2) 4 (Fe3O4)

C. Number of Fe atoms in reactants.

2) 3 (Fe3O4)

Solution

17

Balancing with Polyatomic Ions Polyatomic ions can be balanced as a unit when they

appear on both sides.Pb(NO3)2 + NaCl NaNO3 + PbCl2

Balance NO3- as a unit

Pb(NO3)2 + NaCl 2NaNO3 + PbCl2

2 NO3– = 2 NO3

–

Balance Na (or Cl)Pb(NO3)2 + 2NaCl 2NaNO3 + PbCl2

2Na+ = 2Na+

2Cl– = 2Cl–

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Balance each equation. The coefficients in the answers are read from left to right.

__Mg + __N2 __Mg3N2

1) 1, 3, 2 2) 3, 1, 2 3) 3, 1, 1

B.__Al + __Cl2 __AlCl3

1) 3, 3, 2 2) 1, 3, 1 3) 2, 3, 2

Learning Check

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A. 3) 3, 1, 1 3 Mg + 1 N2 1 Mg3N2

B. 3) 2, 3, 2

2 Al + 3 Cl2 2 AlCl3

Solution

20

A collection term indicates a specific number of items.

For example, 1 dozen doughnuts contains 12 doughnuts.

1 ream of paper means 500 sheets.

1 case is 24 cans.

Collection Terms

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A mole contains 6.02 x 1023 particles, which is the number of carbon atoms in 12.01 g of carbon.

1 mole C = 6.02 x 1023 C atoms The number 6.02 x 1023 is known as Avogadro’s

number. One mole of any element contains Avogadro’s

number of atoms.1 mole Na = 6.02 x 1023 Na atoms1 mole Au = 6.02 x 1023 Au atoms

A Mole

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Avogadro’s number is also the number of molecules and formula units in one mole of a compound.

One mole of a covalent compound contains Avogadro’s number of molecules.1 mole CO2 = 6.02 x 1023 CO2 molecules

1 mole H2O = 6.02 x 1023 H2O molecules One mole of an ionic compound contains

Avogadro’s number of formula units.1 mole NaCl = 6.02 x 1023 NaCl formula units

A Mole of Molecules

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Samples of One Mole Quantities

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A. Calculate the number of atoms in 2.0 moles of Al. 1) 2.0 Al atoms

2) 3.0 x 1023 Al atoms 3) 1.2 x 1024 Al atoms

B. Calculate the number of moles of S in 1.8 x 1024 S. 1) 1.0 mole S atoms 2) 3.0 mole S atoms 3) 1.1 x 1048 mole S atoms

Learning Check

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A. Calculate the number of atoms in 2.0 moles of Al. 3) 1.2 x 1024 Al atoms

2.0 moles Al x 6.02 x 1023 Al atoms1 mole Al

B. Calculate the number of moles of S in 1.8 x 1024 S. 2) 3.0 mole S

1.8 x 1024 S atoms x 1 mole S

6.02 x 1023 S atoms

Solution

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The mass of one mole is called molar mass.

The molar mass of an element is the atomic mass expressed in grams.

Molar Mass

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Give the molar mass to the nearest 0.1 g.

A. 1 mole of K atoms = ________

B. 1 mole of Sn atoms = ________

Learning Check

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Give the molar mass to the nearest 0.1 g.

A. 1 mole of K atoms =39.1 g

B. 1 mole of Sn atoms = 118.7 g

Solution

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Molar Mass of CaCl2

For a compound, the molar mass is the sum of the molar masses of the elements in the formula. We calculate the molar mass of CaCl2 to the nearest 0.1 g as follows.

Element Number of Moles

Atomic Mass Total Mass

Ca 1 40.1 g/mole 40.1 g

Cl2 2 35.5 g/mole 71.0 g

CaCl2 111.1 g

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Molar Mass of K3PO4

Determine the molar mass of K3PO4 to 0.1 g.

Element Number of Moles

Atomic Mass Total Mass in K3PO4

K 3 39.1 g/mole 117.3 g

P 1 31.0 g/mole 31.0 g

O 4 16.0 g/mole 64.0 g

K3PO4 212.3 g

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One-Mole Quantities

32.1 g 55.9 g 58.5 g 294.2 g 342.3 g

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A. 1 mole of K2O = ______g

B. 1 mole of antacid Al(OH)3 = ______g

Learning Check

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A. 1 mole of K2O

2 moles K (39.1 g/mole) + 1 mole O (16.0 g/mole)

78.2 g + 16.0 g = 94.2 g

B. 1 mole of antacid Al(OH)3

1 mole Al (27.0 g/mole) + 3 moles O (16.0 g/mole)+ 3 moles H (1.0 g/mole)

27.0 g + 48.0 g + 3.0 g = 78.0 g

Solution

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Prozac, C17H18F3NO, is an antidepressant that inhibits the uptake of serotonin by the brain. What is the molar mass of Prozac?1) 40.0 g/mole2) 262 g/mole 3) 309 g/mole

Learning Check

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Prozac, C17H18F3NO, is a widely used antidepressant that inhibits the uptake of serotonin by the brain. What is the molar mass of Prozac?

3) 309 g/mole

17C (12.0) + 18H (1.0) + 3F (19.0) + 1N (14.0) + 1 O (16.0) =

204 + 18 + 57.0 + 14.0 + 16.0

Solution

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Methane CH4 known as natural gas is used in gas cook tops and gas heaters.

1 mole CH4 = 16.0 g

The molar mass of methane can be written as conversion factors.

16.0 g CH4 and 1 mole CH4

1 mole CH4 16.0 g CH4

Molar Mass Factors

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Acetic acid C2H4O2 gives the sour taste to vinegar. Write two molar mass conversion factors for acetic acid.

Learning Check

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Acetic acid C2H4O2 gives the sour taste to vinegar. Write two molar mass factors for acetic acid.

1 mole of acetic acid = 60.0 g acetic acid

1 mole acetic acid and 60.0 g acetic acid 60.0 g acetic acid 1 mole acetic acid

Solution

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Mole factors are used to convert between the grams of a substance and the number of moles.

Calculations with Molar Mass

Grams Mole factor Moles

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Aluminum is often used for the structure oflightweight bicycle frames. How many gramsof Al are in 3.00 moles of Al?

3.00 moles Al x 27.0 g Al = 81.0 g Al1 mole Al

mole factor for Al

Calculating Grams from Moles

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The artificial sweetener aspartame (Nutri-Sweet) C14H18N2O5 is used to sweeten diet foods, coffee and soft drinks. How many moles of aspartame are present in 225 g of aspartame?

Learning Check

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Calculate the molar mass of C14H18N2O5.

(14 x 12.0) + (18 x 1.0) + (2 x 14.0) + (5 x 16.0) = 294 g/mole

Set up the calculation using a mole factor. 225 g aspartame x 1 mole aspartame

294 g aspartame

mole factor(inverted)

= 0.765 mole aspartame

Solution

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Conservation of Mass In a chemical reaction, the mass of the reactants

is equal to the mass of the products.

2 moles Ag + 1 mole S = 1 mole Ag2S2 (107.9 g) + 1(32.0 g) = 1 (247.9 g)

247.9 g reactants = 247.9 g product

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We can read the equation in “moles” by placing the word “moles” between each coefficient and formula.4 Fe + 3 O2 2 Fe2O3 4 moles Fe + 3 moles O2 2 moles Fe2O3

Moles in Equations

223.2g 96 g 319.2

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A mole-mole factor is a ratio of the coefficients for two substances. 4 Fe + 3 O2 2 Fe2O3

Fe and O2 4 mole Fe and 3 mole O2

3 mole O2 4 mole Fe

Fe and Fe2O3 4 mole Fe and 2 mole Fe2O3

2 mole Fe2O3 4 mole Fe

O2 and Fe2O3 3 mole O2 and 2 mole Fe2O3

2 mole Fe2O3 3 mole O2

Writing Mole-Mole Factors

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Consider the following equation:

3 H2 + N2 2 NH3

A. A mole factor for H2 and N2 is 1) 3 mole N2 2) 1 mole N2 3) 1 mole N2

1 mole H2 3 mole H2 2 mole H2

B. A mole factor for NH3 and H2 is 1) 1 mole H2 2) 2 mole NH3 3) 3 mole N2

2 mole NH3 3 mole H2 2 mole NH3

Learning Check

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3 H2 + N2 2 NH3

A. A mole factor for H2 and N2 is 2) 1 mole N2

3 mole H2

B. A mole factor for NH3 and H2 is 2) 2 mole NH3

3 mole H2

Solution

48

Consider the following reaction:

4 Fe + 3 O2 2 Fe2O3

How many moles of Fe2O3 are produced when 6.0moles O2 react?

Use the appropriate mole factor to determine themoles Fe2O3.6.0 mole O2 x 2 mole Fe2O3 = 4.0 mole Fe2O3

3 mole O2

Calculations with Mole Factors

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Mass Calculations

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Methanol (CH3OH) burns in air according to the equation

2CH3OH + 3O2 2CO2 + 4H2O

If 209 g of methanol are used up in the combustion, what mass of water is produced?

grams CH3OH moles CH3OH moles H2O grams H2O

molar massCH3OH

coefficientschemical equation

molar massH2O

209 g CH3OH1 mol CH3OH

32.0 g CH3OHx

4 mol H2O

2 mol CH3OHx

18.0 g H2O

1 mol H2Ox =

235 g H2O

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The reaction between H2 and O2 produces 13.1 g of water. How many grams of O2 reacted?

2H2 + O2 2H2O

? g 13.1 g

52

The reaction between H2 and O2 produces 13.1 g of

water. How many grams of O2 reacted?

2H2 + O2 2H2O

? g 13.1 gPlan: g H2O mole H2O mole O2 g O2

13.1 g H2O x 1 mole H2O x 1 mole O2 x 32.0 g O2

18.0 g H2O 2 mole H2O 1 mole O2

= 11.6 g O2

Calculating the Mass of a Reactant

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You prepared cookie dough to make 5 dozen cookies. The phone rings and you answer. While you talk, a sheet of 12 cookies burns. You have to throw them out. The rest of the cookies are okay. The results of our baking can be described as follows:

Theoretical yield 60 cookies possible

Actual yield 48 cookies to eat

Percent yield 48 cookies x 100 = 80% yield 60 cookies

Percent Yield

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Percent Yield The theoretical yield is the maximum amount

of product calculated using the balanced equation.

The actual yield is the amount of product obtained when the reaction is run.

Percent yield is the ratio of actual yield compared to the theoretical yield.

Percent Yield = Actual Yield (g) x 100 Theoretical Yield (g)

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Sample Exercise % Yield

Without proper ventilation and limited oxygen, the reaction of carbon and oxygen produces carbon monoxide.

2C + O2 2CO

What is the percent yield if 40.0 g of CO are produced from the reaction of 30.0 g O2?

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Sample Exercise % Yield (cont.)1. Calculate theoretical yield of CO. 30.0 g O2 x 1 mole O2 x 2 mole CO x 28.0 g CO

32.0 g O2 1 mole O2 1 mole CO= 52.5 g CO (theoretical)

2. Calculate the percent yield. 40.0 g CO (actual) x 100 = 76.2 % yield

52.5 g CO(theoretical)

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Learning Check

In the lab, N2 and 5.0 g of H2 are reactedand produce 16.0 g of NH3. What is thepercent yield for the reaction?

N2(g) + 3H2(g) 2NH3(g)

1) 31.3 %

2) 57%

3) 80.0 %

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Solution

2) 57%

N2(g) + 3H2(g) 2NH3(g)

5.0 g H2 x 1 mole H2 x 2 moles NH3 x 17.0 g NH3

2.0 g H2 3 moles H2 1 mole NH3

= 28 g NH3 (theoretical)

Percent yield = 16.0 g NH3 x 100 = 57 %

28 g NH3

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6.8

Chapter 6 Chemical Reactions

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Combination Decomposition Single Replacement Double Replacement Combustion

Types of Reactions

61

In a combination reaction, two or more elements or simple compounds combine to form one product.A + B AB

ExamplesH2 + Cl2 2HCl

2S + 3O2 2SO3

4Fe + 3O2 2Fe2O3

Combination Reactions

62

In a combination reaction, magnesium and oxygen react to form magnesium oxide.2Mg + O2 2MgO

Combination Reactions

Mg

O2

MgO

63

In a decomposition reaction, one substance is broken down (split) into two or more simpler substances.

AB A + B

2HgO 2Hg + O2

2KClO3 2KCl + 3 O2

Decomposition Reactions

64

Classify the following reactions as

1) combination or 2) decomposition:

___A. H2 + Br2 2HBr

___B. Al2(CO3)3 Al2O3 + 3CO2

___C. 4 Al + 3C Al4C3

Learning Check

65

Classify the following reactions as

1) combination or 2) decomposition:

1 A. H2 + Br2 2HBr

2 B. Al2(CO3)3 Al2O3 + 3CO2

1 C. 4 Al + 3C Al4C3

Solution

66

In a single replacement, one element takes the place of an element in a reacting compound.A + BC AC + BZn(s) + 2HCl(aq) ZnCl2(aq) + H2(g)

Single Replacement

Zn HCl

H2

ZnCl2

67

In a double replacement, the positive ions in the reacting compounds switch places.

AB + CD AD + CB

AgNO3 + NaCl AgCl + NaNO3

ZnS + 2HCl ZnCl2 + H2S

Double Replacement

68

Example of a Double Replacement When solutions of sodium sulfate and barium

chloride are mixed, solid BaSO4 is produced.

BaCl2 + Na2SO4 BaSO4 + 2NaCl

BaSO4

69

Classify each of the following reactions as a

1) single replacement or 2) double replacement

__A. 2Al + 3H2SO4 Al2(SO4)3 + 3H2

__B. Na2SO4 + 2AgNO3 Ag2SO4 + 2NaNO3

__C. 3C + Fe2O3 2Fe + 3CO

Learning Check

70

Classify each of the following reactions as a

1) single replacement or 2) double replacement

1 A. 2Al + 3H2SO4 Al2(SO4)3 + 3H2

2 B. Na2SO4 + 2AgNO3 Ag2SO4 + 2NaNO3

1 C. 3C + Fe2O3 2Fe + 3CO

Solution

71

In a combustion reaction, a reactant often containing carbon reacts with oxygen O2.

C + O2 CO2

CH4 + 2O2 CO2 + 2H2O

C3H8 + 5O2 3CO2 + 4H2O Many combustion reactions utilize fuels that

are burned in oxygen to produce CO2, H2O, and energy.

Combustion

72

Balance the combustion equation:

___C5H12 + ___O2 ___CO2 + ___H2O

Learning Check

73

Balance the combustion equation:

1 C5H12 + 8 O2 5 CO2 + 6 H2O

Solution

74

Reaction of lead nitrate with sodium Iodide

PbI2

75

Class of Chemical Reactions01

Precipitation Reactions: A process in which an insoluble solid precipitate drops out of the solution.

Most precipitation reactions occur when the anions and cations of two ionic compounds change partners.

Pb(NO3)2(aq) + 2 NaI(aq) 2 NaNO3(aq) + PbI2(s)

76

Types of Chemical Reactions02 Acid–Base Neutralization: A process in which an

acid reacts with a base to yield water plus an ionic compound called a salt.

The driving force of this reaction is the formation of the stable water molecule.

HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l)

77

Types of Chemical Reactions03 Oxidation–Reduction (Redox) Reaction: A

process in which one or more electrons are transferred between reaction partners.

The driving force of this reaction is the decrease in electrical potential.

4 Fe + 3 O2 2 Fe2O3

78

Reaction of lead nitrate with sodium Iodide

PbI2

79

Precipitation Reactions

Precipitate – insoluble solid that separates from solution

molecular equation

ionic equation

net ionic equation

Pb2+ + 2NO3- + 2Na+ + 2I- PbI2 (s) + 2Na+ + 2NO3

-

Na+ and NO3- are spectator ions

PbI2

Pb(NO3)2 (aq) + 2NaI (aq) PbI2 (s) + 2NaNO3 (aq)

precipitate

Pb2+ + 2I- PbI2 (s)

80

Writing Net Ionic Equations

1. Write the balanced equation (molecular equation).

2. Write the ionic equation showing the water soluble compounds in their ionic forms.

3. Determine precipitate from solubility rules

4. Cancel the spectator ions on both sides of the ionic equation

AgNO3 (aq) + NaCl (aq) AgCl (s) + NaNO3 (aq)

Ag+ + NO3- + Na+ + Cl- AgCl (s) + Na+ + NO3

-

Ag+ + Cl- AgCl (s)

Write the net ionic equation for the reaction of silver nitrate with sodium chloride in water.

81

82

Chapter 6 Chemical Reactions

6.12 Redox Reactions

83

Oxidation and reduction Are an important type of

reaction. Provide us with energy

from food. Provide electrical energy

in batteries. Occur when iron rusts.

4Fe + 3O2 2Fe2O3

Oxidation and Reduction

84

An oxidation-reduction reaction involves the transfer of electrons from one reactant to another.

In oxidation, electrons are lost. Zn Zn2+ + 2e- (loss of electrons) In reduction, electrons are gained.

Cu2+ + 2e- Cu (gain of electrons)

Electron Loss and Gain

85

Half-Reactions for Oxidation-Reduction

In the oxidation-reduction reaction of zinc and copper(II) sulfate, the zinc is oxidized and the Cu2+ (from Cu2+ SO4

2-) is reduced.

Zn Zn2+ + 2e- oxidationCu2+ + 2e- Cu reduction

86

Redox Reactions 02

87

Identify each of the following as an

1) oxidation or a 2) reduction:

__A. Sn Sn4+ + 4e-

__B. Fe3+ + 1e- Fe2+

__C. Cl2 + 2e- 2Cl-

Learning Check

88

Identify each of the following as an

1) oxidation or a 2) reduction:

1 A. Sn Sn4+ + 4e-

2 B. Fe3+ + 1e- Fe2+

2 C. Cl2 + 2e- 2Cl-

Solution

89

In a balanced oxidation-reduction equation, the loss of electrons is equal to the gain of electrons.Zn + Cu2+ Zn2+ + Cu

The loss and gain of two electrons is shown in the separate oxidation and reduction reactions.Zn Zn2+ + 2e- oxidationCu2+ + 2e- Cu reduction

Balanced Red-Ox Equations

90

In light-sensitive sunglasses, UV light initiatesan oxidation-reduction reaction. uv light

Ag+ + Cl- Ag + ClA. Which reactant is oxidized?

1) Ag+ 2) Cl- 3) AgB. Which reactant is reduced?

1) Ag+ 2) Cl- 3) Cl

Learning Check

91

In light-sensitive sunglasses, UV light initiatesan oxidation-reduction reaction.

uv light

Ag+ + Cl– Ag + ClA. Which reactant is oxidized

2) Cl– Cl– Cl + e–

B. Which reactant is reduced?1) Ag+ Ag+ + e– Ag

Solution

92

Write the separate oxidation and reduction half reactions for the following equation.

2Cs + F2 2CsF

Learning Check

93

Write the separate oxidation and reduction reactions for the following equation.

2Cs + F2 2CsF

2Cs 2Cs+ + 2e– oxidation

F2 + 2e– 2F- reduction

Solution

94

An early definition of oxidation is the addition of oxygen O2 to a reactant.

A metal or nonmetal is oxidized while the O2 is reduced to O2-.

4K + O2 2K2O

C + O2 CO2

2SO2 + O2 2SO3

Oxidation with Oxygen

95

In organic and biological reactions, oxidation involves the loss of hydrogen atoms and reduction involves a gain of hydrogen atoms. oxidation = Loss of Hreduction = Gain of HCH3OH H2CO + 2H (loss of H)Methanol Formaldehyde

Gain and Loss of Hydrogen

96

Oxidation–Reduction Reactions02

Oxidation

Is

Loss (of electrons)

Anode Oxidation

Reducing Agent

97

Oxidation–Reduction Reactions03

Reduction

Is

Gain (of electrons)

Cathode Reduction

Oxidizing Agent

98

Rule Applies to Statement1 Elements The oxidation number of an atom in an

element is zero.

2 Monatomic ions

The oxidation number of an atom in a monatomic ion equals the charge of the ion.

3 Oxygen The oxidation number of oxygen is –2 in most of its compounds. (An exception is O in H2O2 and other peroxides, where the oxidation number is –1.)

OxidationNumber Rules

99

Oxidation Number Rules

Rule Applies to Statement4 Hydrogen +1, it will be -1 when hydrogen comes with

metal. NaH

5 Halogens Fluorine is –1 in all its compounds. Each of the other halogens is –1 in binary compounds unless the other element is oxygen.

6 Compounds and ions

The sum of the oxidation numbers of the atoms in a compound is zero. The sum in a polyatomic ion equals the charge on the ion.

100

HCO3-

O = -2 H = +1

3x(-2) + 1 + ? = -1

C = +4

Oxidation numbers of all the elements in HCO3

- ?

101

NaIO3

Na = +1 O = -2

3x(-2) + 1 + ? = 0

I = +5

IF7

F = -1

7x(-1) + ? = 0

I = +7

K2Cr2O7

O = -2 K = +1

7x(-2) + 2x(+1) + 2x(?) = 0

Cr = +6

Oxidation numbers of all the elements in the following ?

102

Chapter Summary Chemical equations must be balanced, that is, the

numbers and kinds of atoms must be the same in the reactants and the products.

To balance an equation, coefficients are placed before formulas.

The coefficients in a balanced equation represent the numbers of moles of reactants and products in a reaction.

A mole refers to Avogadro’s number (6.022x1023) of formula units of a substance.

103

One mole of any substance has a mass equal to the molecular or formula weight of the substance in grams.

The ratios of coefficients act as mole ratios that relates amounts of reactants and/or products.

The yield of a reaction is the amount of product obtained.

The percent yield is the amount of product obtained divided by the amount theoretically possible and multiplied by 100.

Chapter Summary Contd.

104

Three common types of reactions of ionic compounds are:

Precipitation reactions Acid-base neutralization reaction Oxidation-reduction reactions

By comparing the oxidation numbers of an atom before and after reaction, we can tell whether the atom has gained or lost shares in electrons and thus whether a redox reaction has occurred.

Oxidation numbers are assigned to atoms in reactants and products to provide a measure for whether an atom is neutral, electron-rich, or electron-poor.

Chapter Summary Contd.

105

End of Chapter Six

106

Personal Response System Questionsfor use withFundamentals of General, Organic, and Biological Chemistry, 5th ed.Media Update EditionMcMurry and Castellion

Chapter 6

107

Assume the mixture of substances in drawing (a) undergoes a reaction. Which of the drawings (b)-(d) represents a product mixture consistent with the law of mass conservation?

1. All drawings (b)-(d)

2. Only drawing (b)

3. Only drawing (c)

4. Only drawing (d)(a)

(b) (c) (d)

108

Assume the mixture of substances in drawing (a) undergoes a reaction. Which of the drawings (b)-(d) represents a product mixture consistent with the law of mass conservation?

1. All drawings (b)-(d)

2. Only drawing (b)

3. Only drawing (c)4. Only drawing (d)

(a)

(b) (c) (d)

109

Reaction of A (unshaded spheres) with B (shaded spheres is shown schematically in the diagram below. Which equation best describes the reaction?

1. A + B AB

2. 4 A + 2 B 4 AB

3. A2 + B2 A2B

4. 2 A2 + B2 2 A2B

110

Reaction of A (unshaded spheres) with B (shaded spheres is shown schematically in the diagram below. Which equation best describes the reaction?

1. A + B AB

2. 4 A + 2 B 4 AB

3. A2 + B2 A2B

4. 2 A2 + B2 2 A2B

111

a CH3CH2OH + b O2 c CO2 + d H2O

When the above equation is balanced, the coefficients a, b, c, and d are

1. a=1, b=1, c=1, d=1

2. a=1, b=2, c=2, d=3

3. a=1, b=3, c=2, d=3

4. a=2, b=7, c=4, d=6

112

a CH3CH2OH + b O2 c CO2 + d H2O

When the above equation is balanced, the coefficients a, b, c, and d are

1. a=1, b=1, c=1, d=1

2. a=1, b=2, c=2, d=3

3. a=1, b=3, c=2, d=3

4. a=2, b=7, c=4, d=6

113

Which of the following reactions is an acid-base neutralization reaction?

1. AgNO3(aq) + NaBr(aq) AgBr(s) + NaNO3(aq)

2. 2 CH3OH(l) + 3 O2 (g) 2 CO2(g) + 4 H2O(l)

3. 2 Na(s) + Br2(l) 2 NaBr(s)

4. H2SO4(aq) + 2 KOH(aq) 2 H2O(l) + K2SO4(aq)

114

Which of the following reactions is an acid-base neutralization reaction?

1. AgNO3(aq) + NaBr(aq) AgBr(s) + NaNO3(aq)

2. 2 CH3OH(l) + 3 O2 (g) 2 CO2(g) + 4 H2O(l)

3. 2 Na(s) + Br2(l) 2 NaBr(s)

4. H2SO4(aq) + 2 KOH(aq) 2 H2O(l) + K2SO4(aq)

115

Predict which of the following solutions will result in a precipitation reaction.

1. Cr(NO3)3(aq) + KCl(aq)

2. CuCl2(aq) + Na2S(aq)

3. NH4Br(aq) + Na2SO4(aq)

4. CsOH(aq) + RbCl(aq)

116

Predict which of the following solutions will result in a precipitation reaction.

1. Cr(NO3)3(aq) + KCl(aq)

2. CuCl2(aq) + Na2S(aq)

3. NH4Br(aq) + Na2SO4(aq)

4. CsOH(aq) + RbCl(aq)

117

Identify the oxidized reactant, the reduced reactant, the oxidizing agent, and the reducing agent in the reaction: Fe2O3(s) + 3 CO(g) 2 Fe(s) + 3 CO2(g).

1. CO(g) is oxidized and is the oxidizing agent and Fe2O3(s) is reduced and is the reducing agent.

2. CO(g) is oxidized and is the reducing agent and Fe2O3(s) is reduced and is the oxidizing agent.

3. CO(g) is reduced and is the oxidizing agent and Fe2O3(s) is oxidized and is the reducing agent.

4. CO(g) is reduced and is the reducing agent and Fe2O3(s) is oxidized and is the oxidizing agent.

118

Identify the oxidized reactant, the reduced reactant, the oxidizing agent, and the reducing agent in the reaction: Fe2O3(s) + 3 CO(g) 2 Fe(s) + 3 CO2(g).

1. CO(g) is oxidized and is the oxidizing agent and Fe2O3(s) is reduced and is the reducing agent.

2. CO(g) is oxidized and is the reducing agent and Fe2O3(s) is reduced and is the oxidizing agent.

3. CO(g) is reduced and is the oxidizing agent and Fe2O3(s) is oxidized and is the reducing agent.

4. CO(g) is reduced and is the reducing agent and Fe2O3(s) is oxidized and is the oxidizing agent.