Chapter 5 Chemical Reactions -...

12/17/2016

1

Chapter 5 Chemical Reactions

1. Physical and Chemical Changes

2. Understanding Chemical Changes

3. Chemical Equations

4. Balancing Chemical Equations

5. Types of Chemical Reactions

Table of Contents

Chapter 5

• List down some changes around you and identify them as physical and chemical.

Warm up

• Which changes in your list are reversible and which are irreversible?

• Which changes in your list produce new substances?


12/17/2016

2

Chapter 5 1. Physical and Chemical Changes

• Physical changes are changes in which the identity of a substance does not change. Chemical composition of substances remain unchanged. Breaking of a glass, cutting of a sheet of paper, dissolving of salt in water, freezing of water…etc are physical changes.

• No new substance is formed.• Some physical changes are reversible.


• Changes that cause to produce new substances are

called chemical changes. The rusting of iron, boiling

of an egg, spoiling fruits, burning of coal…etc. are

chemical changes. Chemical changes usually

irreversible.

12/17/2016

3



12/17/2016

4


Chapter 5

Section Review1. Identify the following changes as physical or chemical.

Burning of wood, evaporation of alcohol, freezing of

cement, frying of egg, souring of milk, digging of soil,

painting of a wall, cleaning of dishes.


1. Chemical changes: Burning of wood, frying of egg,

souring of milk, cleaning of dishes.

Physical changes: Evaporation of alcohol, digging of

soil, painting of a wall

12/17/2016

5

Chapter 5

Section Review

2. Which of the following changes is different?

A. Raining

B. Sublimation of iodine

C. Combustion of gasoline

D. Distillation of petroleum


Chapter 5

Section Review

2. Which of the following changes is different?

A. Raining

B. Sublimation of iodine

C. Combustion of gasoline

D. Distillation of petroleum


12/17/2016

6

Chapter 5

Section Review

3. Wood that has burned and formed carbon dioxide and

water vapor has gone through a

A. chemical change

B. physical change

C. change in state

D. change in color.


Chapter 5

Section Review

3. Wood that has burned and formed carbon dioxide and

water vapor has gone through a

A. chemical change

B. physical change

C. change in state

D. change in color.


12/17/2016

7

Chapter 5

• List some evidences that suggest that a chemical reaction has occurred and decide which of them might be indicator for the following changes.

Cooking of cake, photosynthesis, burning of paper, spoiling of fruits, cleaning of a cloth.

Warm up

2. Understanding Chemical Changes

Chapter 5 2. Understanding Chemical Changes

12/17/2016

8



Evidence of a Chemical Reaction, continued

2. Color ChangePb(NO3)2 + 2KI PbI2 + 2KNO3

yellow ppt

1. Solid Formation (precipitation)3NaOH + AlCl3 Al(OH)3 + 3NaCl

white ppt

12/17/2016

9





12/17/2016

10



3. Gas ReleaseCaCO3 + 2HCl CaCl2 + CO2 + H2O

4. Heat Exchange2Al + Fe2O3 2Fe + Al2O3 + Energy



12/17/2016

11




Section Review

1. What are the indicators for the chemical reaction of

combustion of gasoline in engines?

1. Gas formation, heat exchange, color change

12/17/2016

12


Section Review

2. Which observation does NOT indicate that a chemical

reaction has occurred?

A. formation of a precipitate

B. production of a gas

C. evolution of energy

D. change in total mass of substances


Section Review

2. Which observation does NOT indicate that a chemical

reaction has occurred?

A. formation of a precipitate

B. production of a gas

C. evolution of energy

D. change in total mass of substances

12/17/2016

13


Section Review

3. A solid produced by a chemical reaction that then

separates from the solution is called a(n) _________ .

3. A solid produced by a chemical reaction that then

separates from the solution is called a(n) precipitate.

Chapter 5

• Write some word equations that represent the chemical changes given below.

Baking a cake, souring milk, burning a piece of paper, rusting iron

Warm up

3. Chemical Equations

12/17/2016

14

Chapter 5 3. Chemical Equations

• A chemical equation shows the chemical formulas

and relative amounts of all reactants and products.

• A substance that undergoes a reaction is called a

reactant.

• When reactants undergo a chemical change, each

new substance formed is called a product.

methane + oxygen carbon dioxide + water

CH4 + O2 CO2 + H2O


12/17/2016

15



12/17/2016

16


• In chemical reactions following properties remain constant.

• Types and number of reacting atoms,

• Total mass of substances.

• Total number of protons, neutrons, and electrons.

• In chemical reactions following properties may change.

• Number of electrons and electronic configurations of

atoms.

• Total number of moles, molecules and volumes.

• Physical properties like color, odor, taste and states.


Section Review

1. Knowledge about what products are produced in a

chemical reaction is obtained by

A. inspecting the chemical equation.

B. balancing the chemical equation.

C. laboratory analysis.

D. writing a word equation.

12/17/2016

17


Section Review

1. Knowledge about what products are produced in a

chemical reaction is obtained by

A. inspecting the chemical equation.

B. balancing the chemical equation.

C. laboratory analysis.

D. writing a word equation.


Section Review

2. A chemical reaction has NOT occurred if the

products have

A. the same mass as the reactants.

B. less total bond energy than the reactants.

C. more total bond energy than the reactants.

D. the same chemical properties as the reactants.

12/17/2016

18


Section Review

2. A chemical reaction has NOT occurred if the

products have

A. the same mass as the reactants.

B. less total bond energy than the reactants.

C. more total bond energy than the reactants.

D. the same chemical properties as the reactants.


Section Review

3. Which word equation represents the reaction that

produces water from hydrogen and oxygen?

A. Water is produced from hydrogen and oxygen.

B. Hydrogen plus oxygen yields water.

C. H2 + O2 water.

D. Water can be separated into hydrogen and oxygen.

12/17/2016

19


Section Review

3. Which word equation represents the reaction that

produces water from hydrogen and oxygen?

A. Water is produced from hydrogen and oxygen.

B. Hydrogen plus oxygen yields water.

C. H2 + O2 water.

D. Water can be separated into hydrogen and oxygen.


Section Review

4. How would oxygen be represented in the formula

equation for the reaction of methane and oxygen to

yield carbon dioxide and water?

A. oxygen

B. O2

C. O

D. O3

12/17/2016

20


Section Review

4. How would oxygen be represented in the formula

equation for the reaction of methane and oxygen to

yield carbon dioxide and water?

A. oxygen

B. O2

C. O

D. O3


Section Review

5. In an equation, the symbol for a substance in water

solution is followed by

A. (l).

B. (g).

C. (aq).

D. (s).

12/17/2016

21


Section Review

5. In an equation, the symbol for a substance in water

solution is followed by

A. (l).

B. (g).

C. (aq).

D. (s).


Section Review

6. Photosynthesis is the process plants use to make

glucose and oxygen gas from carbon dioxide and

water only in the presence of light. Write a word

equation for the reaction.

6. carbon dioxide + water glucose + oxygensunlight

12/17/2016

22


Section Review

7. Solid CuO and gaseous CH4 are combined and

heated. The products are solid copper, carbon

dioxide gas, and water vapor.

7. Consider the reaction;

4CuO(s) + CH4(g) 4Cu(s) + CO2(g) + 2H2O(g).

Describe this reaction in terms of states of matter and

the conditions required for the reaction to happen.

Chapter 5

• Describe the mass change in the burning of a wood.

• Think a way that proves mass does not change in

chemical reactions.

Warm up


12/17/2016

23

Chapter 5 4. Balancing Chemical Equations

Chapter 5

• The law of conservation of mass states that mass is

neither created nor destroyed during chemical reactions.

Total mass is constant in a chemical reaction. This is

known as Lavoisier’s Law.

Conservation of Mass


12/17/2016

24

Chapter 5

Conservation of Mass, continued


Chapter 5

• The number of atoms for each element must be the same

on the reactants’ side and on the products’ side.

• A coefficient multiplies the number of atoms of each

element in the formula that follows.


• H2O: 2 hydrogen atoms, 1 oxygen atom

• 2H2O: 4 hydrogen atoms, 2 oxygen atoms

12/17/2016

25


Chapter 5

• Below are some tips for balancing equations:

• Take the coefficients of the most complex compound

as one.

• Balance the elements found in this most complex

compound first.

• Balance the elements last that is free in reactants or

products.

• Balance oxygen and hydrogen atoms at the end.

• Never change the subscripts.


12/17/2016

26


Sample Problem ABalance the equation for the reaction of iron(III) oxide with hydrogen to form iron and water.

Sample Problem A Solution

Fe2O3 + H2 Fe + H2O1 3 32


Sample Problem BBalance the equation below with integer numbers.

Na + H2O NaOH + H2

Sample Problem B Solution

Na + H2O NaOH + H21 1 ½ 1

Then,2Na + 2H2O 2NaOH + 1H2

12/17/2016

27


Sample Problem CAluminum reacts with arsenic acid, HAsO3, to form H2

and aluminum arsenate. Write a balanced equation for this reaction.

Sample Problem C

Al + HAsO3 H2 + Al(AsO3)3 132

31

Then,2Al + 6HAsO3 3H2 + 2Al(AsO3)3


Sample Problem DFind the unknown substance represented by X in the following balanced equation.

4FeS2 + 11O2 2Fe2O3 + 8X

Sample Problem D

4FeS2 + 11O2 2Fe2O3 + 8SO2

12/17/2016

28


Chapter 5

Section Review

1. What is the small whole number that appears in front

of a formula in a chemical equation?

A. a subscript

B. a superscript

C. a ratio

D. a coefficient


12/17/2016

29

Chapter 5

Section Review

1. What is the small whole number that appears in front

of a formula in a chemical equation?

A. a subscript

B. a superscript

C. a ratio

D. a coefficient


Chapter 5

Section Review

2. According to the law of conservation of mass, the

total mass of the reacting substances is

A. always more than the total mass of the products.

B. always less than the total mass of the products.

C. sometimes more and sometimes less than the total

mass of the products.

D. always equal to the total mass of the products.


12/17/2016

30

Chapter 5

Section Review

2. According to the law of conservation of mass, the

total mass of the reacting substances is

A. always more than the total mass of the products.

B. always less than the total mass of the products.

C. sometimes more and sometimes less than the total

mass of the products.

D. always equal to the total mass of the products.


Chapter 5

Section Review

3. A chemical equation is balanced when the

A. coefficients of the reactants equal the coefficients of

the products.

B. same number of each kind of atom appears in the

reactants and in the products.

C. products and reactants are the same chemicals.

D. subscripts of the reactants equal the subscripts of the

products.


12/17/2016

31

Chapter 5

Section Review

3. A chemical equation is balanced when the

A. coefficients of the reactants equal the coefficients of

the products.

B. same number of each kind of atom appears in the

reactants and in the products.

C. products and reactants are the same chemicals.

D. subscripts of the reactants equal the subscripts of

the products.


Chapter 5

Section Review

4. When the equation Fe3O4 + Al Al2O3 + Fe is

correctly balanced, what is the coefficient of Fe?

A. 3 B. 4 C. 6 D. 9


12/17/2016

32

Chapter 5

Section Review

4. When the equation Fe3O4 + Al Al2O3 + Fe is

correctly balanced, what is the coefficient of Fe?

A. 3 B. 4 C. 6 D. 9


Chapter 5

Section Review

5. Which coefficients correctly balance the formula

equation

NH4NO2(s) N2(g) + H2O(l)?

A. 1, 2, 2

B. 1, 1, 2

C. 2, 1, 1

D. 2, 2, 2


12/17/2016

33

Chapter 5

Section Review

5. Which coefficients correctly balance the formula

equation

NH4NO2(s) N2(g) + H2O(l)?

A. 1, 2, 2

B. 1, 1, 2

C. 2, 1, 1

D. 2, 2, 2


Chapter 5

Section Review

6. What is the formula of the compound represented by

X in the following balanced equation?

2Ag + 2H2SO4 Ag2SO4 + SO2 + 2X


6. H2O

12/17/2016

34

Chapter 5

Section Review

7. How many grams of water is produced from 8 g

hydrogen and 64 g oxygen gases?


7. 2H2 + O2 2H2OFollowing the conservation of mass lawmreactants= mproducts

8 g + 64 = 72 g H2O will be produced

Chapter 5

• Describe the following terms

Synthesis, Analysis, Decomposition, Combination,

Oxidation, Combustion, Neutralization, Displacement

• What kind of reactions exist in human body?

Warm up


12/17/2016

35

Chapter 5

• Whenever two or more substances combine to form a single product, the reaction is called a synthesisreaction.

• Combination reactions can be illustrated;

A + B AB

1. Combination (Synthesis) Reactions


• Here are some examples;C + O2 CO2

4Fe + 3O2 2Fe2O3

CaO + H2O Ca(OH)2

N2 + 3H2 2NH3

12/17/2016

36

Chapter 5

1. Combination (Synthesis) Reactions, continued


Chapter 5



12/17/2016

37

Chapter 5



Chapter 5



12/17/2016

38

Chapter 5



Chapter 5



12/17/2016

39

Chapter 5



Chapter 5

• In a decomposition reaction a single compound breaks down, often with the input of energy, into two or more elements or simpler compounds.

• Decomposition reactions can be illustrated;

AB A + B

2. Decomposition (Analysis) Reactions


• Here are some examples;

NH4NO3 N2O + 2H2O

2H2O2 2H2O + O2

2NaCl 2Na + Cl2

PCl5 PCl3 + Cl2

Electricity

12/17/2016

40

Chapter 5

2. Decomposition (Analysis) Reactions, continued


Chapter 5

• In a displacement reaction a single element reacts with a compound and displaces another element from the compound.

• Displacement reactions can be illustrated;

A + BC B + AC

3. Single Displacement Reactions


• Single displacement reactions mostly take place due to activity differences of elements. A more active element displaces a less active one.

Zn(s) + CuSO4(aq) Cu(s) + ZnSO4(aq)

Fe(s) + NaCl(aq) No reaction

12/17/2016

41

Chapter 5

3. Single Displacement Reactions, continued


Chapter 5



12/17/2016

42

Chapter 5



Chapter 5



Activity of Some Metals

Li Rb K Ba Sr Ca Na Mg Al Mn Zn Cr Cd Fe Co Ni Sn Pb H Cu Hg Ag Pt Au

Activity Decreases

Activity of Some Nonmetals

F Cl Br I Activity Decreases

• Some examples;

NaBr(aq) + Cl2(g) 2NaCl(aq) + Br2(g)

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

Mg(s) + 2CuCl(aq) MgCl2(aq) + 2Cu(s)

12/17/2016

43

Chapter 5



Chapter 5



12/17/2016

44

Chapter 5



Chapter 5

• In a double-displacement reaction two compounds in aqueous solution appear to exchange ions and form two new compounds.

• One of the products must be a solid precipitate, a gas, or a molecular compound, such as water.

• Double displacement reactions can be illustrated;

AB + CD AD + CB

4. Double Displacement (Metathesis) Reactions


• Some examples;

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

Pb(NO3)2(aq) + K2CrO4(aq) PbCrO4(ppt) + 2KNO3(aq)

12/17/2016

45

Chapter 5



Chapter 5 5. Types of Chemical Reactions


12/17/2016

46

Chapter 5

• A reaction which absorbs energy is endothermic reactionand which release energy is exothermic reaction.

5. Endothermic and Exothermic Reactions


• Some examples;

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

Exothermic Reaction

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

Endothermic Reaction

Chapter 5



12/17/2016

47

Chapter 5



Chapter 5

• A combustion reaction is a reaction of a carbon-based

compound with oxygen.

6. Combustion Reactions


• Some examples;

C3H8 + 5O2 3CO2 + 4H2O + heat

CH3CH2OH + 3O2 2CO2 + 3H2O + heat

C6H12O6 + 6O2 6CO2 + 6H2O + heat

12/17/2016

48

Chapter 5



Chapter 5



12/17/2016

49

Chapter 5

6. Combustion Reactions, continued


Chapter 5

6. Combustion Reactions, continued


12/17/2016

50

Chapter 5 5. Types of Chemical Reactions

Chapter 5

Section Review

1. In what kind of reaction do two or more substances combine to form a new compound?

A. decomposition reaction

B. double-displacement reaction

C. ionic reaction

D. synthesis reaction


12/17/2016

51

Chapter 5

Section Review

1. In what kind of reaction do two or more substances combine to form a new compound?


B. double-displacement reaction

C. ionic reaction

D. synthesis reaction


Chapter 5

Section Review

2. In what kind of reaction does a single compound produce two or more simpler substances?


B. displacement reaction

C. synthesis reaction

D. ionic reaction


12/17/2016

52

Chapter 5

Section Review

2. In what kind of reaction does a single compound produce two or more simpler substances?


B. displacement reaction

C. synthesis reaction

D. ionic reaction


Chapter 5

Section Review

3. The reaction 2KClO3(s) 2KCl(s) + 3O2(g) is a(n)

A. synthesis reaction.

B. combustion reaction.

C. decomposition reaction.

D. ionic reaction.


12/17/2016

53

Chapter 5

Section Review

3. The reaction 2KClO3(s) 2KCl(s) + 3O2(g) is a(n)


B. combustion reaction.

C. decomposition reaction.

D. ionic reaction.


Chapter 5

Section Review

4. In what kind of reaction does one element replace a

similar element in a compound?

A. displacement reaction

B. decomposition reaction

C. combustion

D. ionic reaction


12/17/2016

54

Chapter 5

Section Review

4. In what kind of reaction does one element replace a

similar element in a compound?

A. displacement reaction

B. decomposition reaction

C. combustion

D. ionic reaction


Chapter 5

Section Review

5. The reaction Cl2(g) + 2KBr(aq) 2KCl(aq) + Br2(l)

is a(n)


B. displacement reaction.

C. ionic reaction.

D. combustion reaction.


12/17/2016

55

Chapter 5

Section Review

5. The reaction Cl2(g) + 2KBr(aq) 2KCl(aq) + Br2(l)

is a(n)


B. displacement reaction.

C. ionic reaction.

D. combustion reaction.


Chapter 5

Section Review

6. A precipitate forms in a double-displacement reaction

when

A. hydrogen gas reacts with a metal.

B. positive ions combine with negative ions.

C. water boils out of the solution.

D. a gas escapes.


12/17/2016

56

Chapter 5

Section Review

6. A precipitate forms in a double-displacement reaction

when

A. hydrogen gas reacts with a metal.

B. positive ions combine with negative ions.

C. water boils out of the solution.

D. a gas escapes.


Chapter 5

Section Review

7. I. K2CO3 + Cr II. ZnI2 + Br2 III. CuSO4 + Zn

Which of the above reaction(s) take place underappropriate conditions?

A. I only B. II only C. II and III D. I and llI


12/17/2016

57

Chapter 5

Section Review

7. I. K2CO3 + Cr II. ZnI2 + Br2 III. CuSO4 + Zn

Which of the above reaction(s) take place underappropriate conditions?

A. I only B. II only C. II and III D. I and Ill


Chapter 5

Section Review

8. Which of the following is a combustion reaction?

A. N2 + 3H2 2NH3

B. H2O H2 + 1/2O2

C. CaCO3 + heat CaO + CO2

D. C3H8 + 5O2 3CO2 + 4H2O


12/17/2016

58

Chapter 5

Section Review

8. Which of the following is a combustion reaction?

A. N2 + 3H2 2NH3

B. H2O H2 + 1/2O2

C. CaCO3 + heat CaO + CO2

D. C3H8 + 5O2 3CO2 + 4H2O


End of the chapter

Date post:	20-Jul-2018
Category:	Documents
Upload:	hoangdieu
View:	235 times
Download:	0 times

Chapter 5 Chemical Reactions -...

Documents