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Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process...

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Unit 8 Unit 8 Chemical Reactions Chemical Reactions PAGE 123 PAGE 123
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Page 1: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Unit 8 Unit 8 Chemical ReactionsChemical Reactions

Unit 8 Unit 8 Chemical ReactionsChemical Reactions

PAGE 123PAGE 123

Page 2: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Describing Chemical Reactions

• A chemical reaction is the process by which one or more substances are changed into one or more different substances.

•They are described by chemical equations

Page 3: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Describing Chemical Reactions

• In a chemical reaction:– bonds are broken in the reactants

–Bonds are formed in the products

Page 4: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Parts of a Chemical Parts of a Chemical EquationEquation

Parts of a Chemical Parts of a Chemical EquationEquation

Page 5: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Reactants•original substances in a chemical reaction

•written on the left hand side of a chemical equation

Page 6: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Products•The resulting substances produced in a chemical reaction.

•written on the right hand side of the chemical equation

Page 7: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

yields

Page 8: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Subscripts in (parenthesis)

•represents the physical states of the compounds (elements)

•Ex: (s)= solid, (l)=liquid, (g)= gas, (aq)= aqueous (dissolved in water)

Page 9: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.
Page 10: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

•Words or symbols are placed over/under the arrow(s) to indicate certain conditions under which the reaction is carried out.

Page 11: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

– : heat is applied– catalyst

• substance that speeds up a chemical reaction without becoming part of the reaction.

Page 12: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.
Page 13: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.
Page 14: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Law of conservation of mass

According to the law ofconservation of mass, •the total mass of reactants must equal the total mass of products for any given chemical reaction.

Page 15: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Law of conservation of mass

Mass must be equal50 g + 45 g

Balance atoms H2 (g) + O2 (g) H2O (g)22

95g

Page 16: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.
Page 17: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.
Page 18: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.
Page 19: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.
Page 20: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.
Page 21: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.
Page 22: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.
Page 23: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.
Page 24: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Translate Chemical Translate Chemical Equations into WordsEquations into WordsTranslate Chemical Translate Chemical

Equations into WordsEquations into Words

Page 25: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Chemical Equations

•1) include all of the symbols appearing in the equation (with the exception of the

coefficients)

Page 26: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Chemical Equations•3. Diatomic Elements: Elements that combine with each other when found alone in nature

Page 27: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.
Page 28: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Diatomic Elements•7 diatomic elements (know)

H2 O2 F2 Br2 I2 N2 Cl2

Page 29: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Example #2Mg(s) + 2HCl(aq) MgCl2(aq) +

H2(g)Solid magnesium

reacts with

aqueous hydrochloric acid

to produceaqueous magnesium

chlorideand hydrogen gas

Page 30: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Check for Understanding

CaCO3(s) CaO(s) + CO2(g)

Solid calcium carbonate is heated and produces solid calcium oxide and gaseous carbon dioxide

Page 31: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Check for Understanding #2

3KOH(aq) + Fe(NO3)3(aq) Fe(OH)3(s) + 3KNO3(aq)

Aqueous potassium hydroxide reacts with aqueous iron (III) nitrate to produce solid iron (III) hydroxide and aqueous potassium nitrate

Page 32: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Writing Chemical Equations Writing Chemical Equations from a Written from a Written

DescriptionDescription

Writing Chemical Equations Writing Chemical Equations from a Written from a Written

DescriptionDescription

Page 33: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Example #1

Aluminum metal reacts with oxygen in the air to form solid aluminum oxide.

4 Al (s) + O2 (g)3 Al2O3 (s)2

Page 34: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Example #2

When solid mercury(II) sulfide is heated with oxygen gas, liquid mercury metal and gaseous sulfur dioxide are produced.

+ SO2 (g)HgS (s) + O2

(g)

Hg (l)

Page 35: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Check for Understanding

Oxygen gas can be produced by heating solid potassium chlorate in the presence of the catalyst manganese dioxide. Potassium chloride is a solid residue.

MnO2 + O2 (g)2 2 3KClO3 (s) KCl (s)

Page 36: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Check for Understanding

Aqueous potassium nitrate and a precipitate of barium chromate are formed when aqueous solutions of barium nitrate and potassium chromate are mixed.

Page 37: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Check for Understanding

Aqueous potassium nitrate and a precipitate of barium chromate are formed when aqueous solutions of barium nitrate and potassium chromate are mixed.

Ba(NO3)2 (aq) + K2CrO4 (aq)

KNO3 (aq) + BaCrO4 (s)2

Page 38: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Types of Chemical Types of Chemical ReactionsReactions

Types of Chemical Types of Chemical ReactionsReactions

Page 39: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Synthesis (Combination) Reactions

Two or more substances combine to form a new compound.

.

Formation of only ONE product.

Page 40: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Synthesis (Combination) Reactions

Page 41: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Examples:

2H2 + O2 2H2O

CaO + H2O Ca(OH)2

Page 42: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Decomposition Reactions

• A single compound undergoes a reaction that produces two or more simpler substances.

Page 43: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Decomposition Reactions

Page 44: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Decomposition Reactions Decomposition reactions are the opposite of synthesis reactions.

There is only one reactant.

Page 45: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Examples

•CaCO3 CaO + CO2

•Na2CO3 Na2O + CO2

Page 46: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Single-Replacement Reactions

• one element replaces a similar element in a compound.

• a single element reacts with a compound.

Page 47: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Single-Replacement Reactions

Page 48: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Distinguishing Characteristics

• Examples:

Pb + 2HNO3 Pb(NO3)2 + H2

F2 + 2NaI 2NaF + I2

Page 49: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Predict the Products

Zn + CuCl2 ZnCl2 + Cu

Page 50: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Double Replacement Reactions

The ions of two compounds exchange places in an aqueous solution to form two new compounds.

Two ionic compounds “swap” ions.

Page 51: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Double Replacement Reactions

Page 52: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Usually forms a precipitate

• precipitate: when two aqueous solutions are mixed and a solid product that is formed

AgNO3(aq) + KCl(aq) AgCl(s) + KNO3(aq)

Precipitate

Page 53: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Examples

• PbSO4 + 2KCl K2SO4 + PbCl2

• AgNO3(aq) + KCl(aq) ‑‑‑‑> AgCl(s) + KNO3(aq)

Page 54: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Predict the Products

H2O 2KOH + H2SO4 K2SO4 +2HOH

Page 55: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Combustion Reactions

A hydrocarbon (CxHy) combines with oxygen, releasing a large amount of energy in the form of light and heat.

Page 56: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

General Form

CxHy + O2 CO2 + H2O

Page 57: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Example

• C3H8 + 5O2 3 CO2 + 4 H2O

• CH4 + O2 CO2 + H2O

Page 58: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Predict the Products

H2O C2H6 + O2 CO2+2 4 12101 5 2 6

Page 59: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

1) 2 Li + 2 H2O 2 LiOH + H2

single replacement / displacement

Page 60: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

2) NH4Cl NH3 + HCl

decomposition

Page 61: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

3) AgNO3 + NaCl AgCl + NaNO3

double replacement / displacement

Page 62: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

4) 2 C6H14 + 19 O2 12 CO2 + 14 H2O

combustion

Page 63: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

5) N2 + 3 H2 2 NH3

combination / synthesis

Page 64: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Oxidation – Oxidation – ReductionReductionProcessesProcesses

Oxidation – Oxidation – ReductionReductionProcessesProcesses

Page 65: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Redox ReactionAny chemical reaction that involves the transfer of one or more electrons between atoms. One reactant gains electrons and the other reactant loses electrons.

Page 66: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Examples of Redox Reactions

•Combustion of gasoline •Burning of wood•Energy from food•Bleaching stains•Iron rusting

Page 67: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Oxidation and Reduction

• Opposing reactions

•Must occur together–Redox (Reduction – Oxidation)

Page 68: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Oxidation•Electrons are fully or partially

lost

Mg0 (s) Mg 2+ + 2e-

Electrons lost: written as a product

Page 69: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Reduction• Electrons are fully or

partially gained

S0(s) + 2 e- S2-

electrons gained: written as a reactant

Page 70: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Mnemonic Device

• LEO the lion goes GER

LEO: Loss of Electrons is Oxidation

GER: Gain of Electrons is Reduction

Page 71: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Mnemonic Device

•OIL RIG

–Oxidation Is Loss of electrons

–Reduction Is Gain of electrons

Page 72: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Complete Redox Reaction

• Add together the reduction half-reaction with the oxidation half-reaction to get the complete redox reaction.

Page 73: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Complete Redox Reaction

Mg0 (s) Mg 2+ + 2e-

S0(s) + 2 e- S2-

+

Mg0 (s) + S0

(s) Mg 2+ + S2-

Mg + S Mg+2+ S -2

Page 74: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Assigning Oxidation Assigning Oxidation NumbersNumbers

Assigning Oxidation Assigning Oxidation NumbersNumbers

Page 75: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Oxidation Numbers•Numbers assigned to all of

the elements involved in the reaction to determine if electrons have been transferred between atoms in a reaction.

Page 76: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Oxidation Numbers

• The oxidation number is usually equal to the charge on the ion if it was formed.

Page 77: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Rule #1•Free elements are assigned

an oxidation state of 0.

–Al = 0–Na = 0

–H2 = 0

Page 78: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Rule #2• The oxidation state for any

simple one-atom ion is equal to its charge.

–Na+ = +1–Be2+= +2–F- = -1

Page 79: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Rule #3•The alkali metals (Li, Na, K, Rb,

Cs and Fr) in compounds are always assigned an oxidation state of +1.

–LiOH: Li = +1–Na2SO4: Na= +1

Page 80: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Rule #4

•Fluorine in compounds is always assigned an oxidation state of -1.

–HF: F= -1

–MgF2: F= -1

Page 81: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Rule #5• The alkaline earth metals (Be,

Mg, Ca, Sr, Ba, and Ra) and also Zn and Cd in compounds are always assigned an oxidation state of +2. Similarly, Al & Ga are always +3.

•MgF2: Mg = +2

•CaO: Ca= +2

•Al2O3: Al=+3

Page 82: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Rule #6• Hydrogen in compounds is assigned an

oxidation state of +1. 

Exception - Hydrides, ex. LiH (H=-1).

•H2SO4: H=+1

•HCl: H=+1

Page 83: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Rule #7

• Oxygen in compounds is assigned an oxidation state of -2.

Exception - Peroxide, ex. H2O2 (O = -1).

– H3PO4: O=-2

– H2O: O=-2

Page 84: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Rule #8

•The sum of the oxidation numbers of all atoms in a neutral compound is 0.

–H2SO4: add up to 0–CO2: add up to 0

Page 85: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Rule #9

•The sum of the oxidation numbers of all atoms in a polyatomic ion equals the charge on the ion.

–SO42-: add up to -2

–NH4+: add up to +1

Page 86: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Examples•Al(s):

–Al = ____

Rule #1

0

Page 87: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Examples•CaCl2:

–Ca = ____–Cl=____

Rule #5

Ca+2 Rule #8

1 (+2) + 2 (Cl) = 0

Cl = -1

-1

Page 88: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Examples•HNO3:

–H= ____–N= ____–O= ____

Rule # 6

Rule # 7

Rule # 8+1

-2 1(1) + 1(N) + 3(-2) = 0

N = +5

+5

Page 89: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Examples• SO4

2-:

– S= ____– O= ____

Rule #7

-2

Rule #9

1(S) + 4(-2) = -2+6

S= +6

Page 90: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Examples• H2O:

– H= ____– O= ____

Rule #6

+1Rule #7

-2

Page 91: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Examples•(NH4)2CO3

NH4+ CO3

2-

N=____ C=___ H=____ O=___

Rule 6

+1

Rule 7

-2

Rule 9

1(N)+4(+1)=+1N= -3

-3

1(C)+3(-2)=-2C=+4

+4

Page 92: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Check for Understanding

• S8:

– S= ____

• AsO43-:

– As= ____ – O= ____

0

-2+5

Page 93: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Check for Understanding

• Cr(OH)3:

– Cr= ____ – O= ____ – H= ____

-2

+1

+3

OH-

Page 94: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Check for Understanding

• (NH4)3PO4:

– N= ____ – H=_____ – P= ____ – O= ____

NH4+ PO4

-3

+1-3

-2

+5

Page 95: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Oxidized Element

• Atoms that lose electrons in a chemical reaction.

– Elements that lose electrons are undergoing oxidation and are said to be oxidized.

Page 96: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Oxidized Element

• The substance that loses electrons is the oxidized element.

• Atoms that are oxidized will have an increase in their oxidation number

Page 97: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Oxidized Element

Mg0 (s) + S0

(s) Mg 2+ + S2-

Increase in oxidation number

Mg is oxidized

Page 98: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Reduced Element

• Atoms that gain electrons in a chemical reaction.

– Elements that gain electrons are undergoing reduction and are said to be reduced.

Page 99: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Reduced Element

• The substance that gains electrons is the reduced element.

• Atoms that are reduced will have an decrease in their oxidation number

Page 100: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Reduced Element

Mg0 (s) + S0

(s) Mg 2+ + S2-

Decrease in oxidation number

S is reduced

Page 101: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Oxidizing Agent•The element or compound that

is reduced.

•It is called the oxidizing agent because it oxidizes the other element or compound.

Page 102: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Oxidizing Agent

Mg0 (s) + S0

(s) Mg 2+ + S2-

Decrease in oxidation number

S is reduced

S is the oxidizing agent(it is oxidizing Mg)

Page 103: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Reducing Agent•The element or compound that

is oxidized.

• It is called the reducing agent because it reduces the other element or compound.

Page 104: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Reducing Agent

Mg0 (s) + S0

(s) Mg 2+ + S2-

Increase in oxidation number

Mg is oxidizedMg is the reducing agent

(it is reducing S)

Page 105: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Examples

• Are the following redox reactions?

• If yes:– What element is oxidized?– What element is reduced?– What is the oxidizing agent?– What is the reducing agent?

Page 106: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Examples

Mg(s) + S(s) MgS

Step #1: Assign Oxidation Numbers

0 0 +2-2

Step # 2: Do the oxidation numbers change?

- if no it is not a redox reaction

- if yes it is a redox reaction

Yes – It is a redoxWhat element is oxidized?What element is reduced?What is the oxidizing agent?What is the reducing agent?

MgS

SMg

Page 107: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Examples

Step #1: Assign Oxidation Numbers

2AgNO3(aq) + Cu(s) Cu(NO3)2(aq) + 2Ag(s)

0 0

NO3- NO3

-

+1 +2

Yes – It is a redox

Step # 2: Do the oxidation numbers change?

- if no it is not a redox reaction

- if yes it is a redox reaction

What element is oxidized?What element is reduced?What is the oxidizing agent?What is the reducing agent?

CuAg

AgNO3(aq)

Cu(s)

Page 108: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Check for Understanding

• Are the following redox reactions?• If yes:

– What element is oxidized?– What element is reduced?– What is the oxidizing agent?– What is the reducing agent?

Page 109: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Check for Understanding

4Fe(s) + 3O2(g) 2Fe2O3(s)

0 0 -2+3

YesWhat element is oxidized?What element is reduced?What is the oxidizing agent?What is the reducing agent?

FeOO2

Fe

Page 110: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Check for Understanding

Ca(s) + H2O(l) Ca(OH)2(aq) + H2(g)

0 0+1 -2

OH-

+2 +1-2

YesWhat element is oxidized?What element is reduced?What is the oxidizing agent?What is the reducing agent?

CaH

H2OCa

Page 111: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Check for Understanding

HCl + NaOH NaCl + H2O +1-1 +1-2+1 +1-1 +1 -2

No – it is not a redox

Page 112: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Check for Understanding

Fe2O3(s) + 3CO(g) 2Fe(s) + 3CO2(g)

-2 +2-2 0+3 +4-2

YesWhat element is oxidized?What element is reduced?What is the oxidizing agent?What is the reducing agent?

CFe

Fe2O3

CO

Page 113: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Check for Understanding

2AgNO3(aq) + Cu(s) Cu(NO3)2(aq) + 2Ag (s)

NO3- NO3

-

+1 0 +2 +0

YesWhat element is oxidized?What element is reduced?What is the oxidizing agent?What is the reducing agent?

CuAg

AgNO3Cu

Page 114: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Check for Understanding

NaCl + AgNO3 NaNO3 + AgCl+1-1 +1

NO3- NO3

-

+1 +1-1

No – it is not a redox

Page 115: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Check for Understanding

2 H2(g) + O2(g) 2 H2O(l)

0 0 +1-1

YesWhat element is oxidized?What element is reduced?What is the oxidizing agent?What is the reducing agent?

HO

O2H2

Page 116: Unit 8 Chemical Reactions PAGE 123. Describing Chemical Reactions A chemical reaction is the process by which one or more substances are changed into.

Check for Understanding

CH4 + 2 O2 CO2 + 2 H2O -4+1 0 +4-2 +1-2

YesWhat element is oxidized?What element is reduced?What is the oxidizing agent?What is the reducing agent?

CO

O2

CH4


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