chapter 9 honors

Section 9-1

Chemical Reactions

• The process by which one or more substances are rearranged to form different substances is called a chemical reaction. And rummy tummmy

Section 9-1

Chemical Reactions (cont.)

• Evidence of a chemical reaction

– Change in temperature

– Change in color

– Odor, gas, or bubbles may form.

Section 9-1

Representing Chemical Reactions

• Chemists use statements called equations to represent chemical reactions.

• Reactants are the starting substances.

• Products are the substances formed in the reaction.

• This table summarizes the symbols used in chemical equations.

Diatomic elements

• There are 8 elements that never want to be alone.

• They form diatomic molecules.

• H2 , N2 , O2 , F2 , Cl2 , Br2 , I2 , and At2

• The –ogens and the –ines

• 1 + 7 pattern on the periodic table

Section 9-1

Representing Chemical Reactions (cont.)

• In word equations, aluminum(s) + bromine(l) → aluminum bromide(s) reads as “aluminum and bromine react to produce aluminum bromide”.

• Skeleton equations use symbols and formulas to represent the reactants and products.

Al(s) + Br2(l) → AlBr3(s)

• Skeleton equations lack information about how many atoms are involved in the reaction.

Convert these to equations

• Solid iron (III) sulfide reacts with gaseous hydrogen chloride to form iron (II) chloride and hydrosulfuric acid gas.

• Nitric acid dissolved in water reacts with solid sodium carbonate to form liquid water and carbon dioxide gas and sodium nitrate dissolved in water.

The other way

• Fe(s) + O2(g) → Fe2O3(s)

• Cu(s) + AgNO3(aq) →

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

Section 9-1

Representing Chemical Reactions (cont.)

• A chemical equation is a statement that uses chemical formulas to show the identities and relative amounts of the substances involved in a chemical reaction.

Section 9-1

Balancing Chemical Equations

• The most fundamental law in chemistry is the law of conservation of mass.

• Balanced equations show this law.

• Atoms can’t be created or destroyed

• All the atoms we start with we must end up with

• A balanced equation has the same number of each element on both sides of the equation.

Section 9-1

Balancing Chemical Equations

• This figure shows the balanced equation for the reaction between aluminum and bromine.

Section 9-1

Balancing Chemical Equations (cont.)

• A coefficient in a chemical equation is the number written in front of a reactant or product, describing the lowest whole-number ratio of the amounts of all the reactants and products.

Rules for balancing

• 1 Write the correct formulas for all the reactants and products

• 2 & 3 Count the number of atoms of each type appearing on both sides

• 4 Balance the elements one at a time by adding coefficients (the numbers in front)

• 5 Reduce if necessary

• 6 Check to make sure it is balanced.

Never• Never change a subscript to balance an

equation.• If you change the formula you are

describing a different reaction.

• H2O is a different compound than H2O2

• Never put a coefficient in the middle of a formula

• 2 NaCl is okay, Na2Cl is not.

ExampleH2 + H2OO2

→

Make a table to keep track of the elements

Example

H2 + H2OO2→

Need twice as much O in the product

R PH

O

2

2

2

1

Example

H2 + H2OO2→

Changes the O

R PH

O

2

2

2

1

2

Example

H2 + H2OO2→

Also changes the H

R PH

O

2

2

2

1

2

2

Example

H2 + H2OO2→

Need twice as much H in the reactant

R PH

O

2

2

2

1

2

2

4

Example

H2 + H2OO2→

Recount

R PH

O

2

2

2

1

2

2

4

2

Example

H2 + H2OO2→

The equation is balanced, has the same

number of each kind of atom on both sides

R PH

O

2

2

2

1

2

2

4

2

4

Example

H2 + H2OO2→

This is the answer

R PH

O

2

2

2

1

2

2

4

2

4

Not this

Section 9-1

Balancing Chemical Equations (cont.)

Practice

• CH4 + O2 → CO2 + H2O

• AgNO3 + Cu → Cu(NO3)2 + Ag

• Mg + N2 → Mg3N2

• P + O2 → P4O10

• Na + H2O → H2 + NaOH

A. A

B. B

C. C

D. D

Section 9-1

A B C D

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Section 9.1 Assessment

Which of the following is NOT a chemical reaction?

A. a piece of wood burning

B. a car rusting

C. an ice cube melting into water

D. red litmus paper turning blue

A. A

B. B

C. C

D. D

Section 9-1

A B C D

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What is the coefficient of bromine in the equation 2Al(s) + 3Br2(l) → 2AlBr3(s)?

A. 1

B. 2

C. 3

D. 6

Section 9-2

Types of Chemical Reactions

• Chemists classify reactions in order to organize the many types

• We will learn 5 types.• Will be able to predict the products.• For some we will be able to predict

whether they will happen at all.• Will recognize them by the reactants

Section 9-2

Types of Chemical Reactions (cont.)

• When two elements react, the reaction is always a synthesis reaction.

• A synthesis reaction is a reaction in which two or more substances combine to produce a single product.

• Predicting products of a synthesis reaction:

• Element + Element compound

• Fe + O2 Fe2O3 (you would be told iron (III))

– Rules of forming compounds must be followed

• Predict the products– Calcium reacts with chlorine– Aluminum reacts with oxygen


Section 9-2


• In a combustion reaction, oxygen combines with a substance and releases energy in the form of heat and light.

• Heated hydrogen reacts with oxygen to produce heat and water in a combustion reaction. This is also a synthesis reaction.

Last Type

Two specific types of combustion

•If compound composed of only C, H and maybe O is reacted with oxygen, there are two possible outcomes

•Complete combustion will produce CO2 and

H2O.

•Incomplete combustion will produce CO

and H2O.

Examples

Predict Products of combustion reactions:

•C4H10 + O2 → (complete)

•C4H10 + O2 → (incomplete)

•C6H12O6 + O2 → (complete)

•C8H8 + O2 → (incomplete)

•Mg + O2

Section 9-2

Decomposition Reactions

• A decomposition reaction is one in which a single compound breaks down into two or more elements or new compounds.

• Decomposition reactions often require an energy source, such as heat, light, or electricity, to occur.

• Compound Element or compound + Element or compound

#2 Decomposition Reactions

• Predicting Products of Decomposition

• Easily predict the products if it is a binary compound

• Made up of only two elements

• Compound will fall apart into its elements

• H2O

• HgO

electricity → →heat → yelectricit

Section 9-2

Replacement Reactions

• A reaction in which the atoms of one element replace the atoms of another element in a compound is called a single replacement reaction.

A + BX → AX + B

#3 Single Replacement

• We can tell whether a reaction will happen

• Some elements are more reactive than others

• Use Activity Series List• More reactive replaces less reactive

– Higher on the list replaces lower.– If the element by itself is higher, reaction

occurs, if lower it doesn’t

Section 9-2

Replacement Reactions (cont.)


• Fe + CuSO4 →

• Pb + KCl → • Al + HCl →

• What does it mean that Ag, Pt and Au are on the bottom of the Activity Series List?

Section 9-2


• Halogens frequently replace other halogens in replacement reactions.

• Halogens also have different reactivities and do not always replace each other.


• The order of activity is on the periodic table.

• Higher replaces lower.• F2 + HCl →

• Br2 + KCl →

Section 9-2


• Double replacement reactions occur when ions exchange between two compounds.

• This figure shows a generic double replacement equation.

Section 9-2


• A solid product produced during a chemical reaction in a solution is called a precipitate.

• All double replacement reactions produce either water, a precipitate, or a gas.

Complete and balance

Complete and Balance

•assume all of the reactions take place.

•CaCl2 + NaOH →

•CuCl2 + K2S →

•KOH + Fe(NO3)3 →

•(NH4)2SO4 + BaF2 →

Section 9-2


• This table summarizes different ways to predict the products of a chemical reaction.

Examples

• H2 + O2 →

• H2O →

• Zn + H2SO4 →

• HgO →

• KBr +Cl2 →

• AgNO3 + NaCl →

• Mg(OH)2 + H2SO3 →

A. A

B. B

C. C

D. D

Section 9-2

A B C D

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Which of the following is NOT one of the four types of reactions?

A. deconstructive

B. synthesis

C. single replacement

D. double replacement

A. A

B. B

C. C

D. D

Section 9-2


A B C D

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The following equation is what type of reaction?

KCN(aq) + HBr(aq) → KBr(aq) + HCN(g)

A. deconstructive

B. synthesis

C. single replacement

D. double replacement

Section 9-3

Aqueous Solutions

• An aqueous solution contains one or more dissolved substances (called solutes) in water.

• The solvent is the most plentiful substance in a solution.

Section 9-3

Aqueous Solutions (cont.)

• Water is always the solvent in an aqueous solution.

• There are many possible solutes—sugar and alcohol are molecular compounds that exist as molecules in aqueous solutions.

• Compounds that produce hydrogen ions in aqueous solutions are acids.

Section 9-3

Aqueous Solutions (cont.)

• Ionic compounds can also be solutes in aqueous solutions.

• When ionic compounds dissolve in water, their ions separate in a process called dissociation.

Section 9-3

Types of Reactions in Aqueous Solutions

• When two solutions that contain ions as solutes are combined, the ions might react.

• If they react, it is always a double replacement reaction.

• Three products can form: precipitates, water, or gases.

Section 9-3

Types of Reactions in Aqueous Solutions (cont.)

• Aqueous solutions of sodium hydroxide and copper(II) chloride react to form the precipitate copper(II) hydroxide.

2NaOH(aq) + CuCl2(aq) → 2NaCl(aq) + Cu(OH)2(s)

• Ionic equations that show all of the particles in a solution as they actually exist are called complete ionic equations.

2Na+(aq) + 2OH–(aq) + Cu2+ (aq)+ 2Cl–(aq) → 2Na+

(aq) + 2Cl–(aq) + Cu(OH)2(s)

Section 9-3


• Ions that do not participate in a reaction are called spectator ions and are not usually written in ionic equations.

• Formulas that include only the particles that participate in reactions are called net ionic equations.

2OH–(aq) + Cu2+(aq) → Cu(OH)2(s)

Section 9-3


• Some reactions produce more water molecules.

• No evidence of a chemical reaction is observable.

HBr(aq) + NaOH(aq) → H2O(l) + NaBr(aq)

• Without spectator ions H+(aq) + OH–(aq) → H2O(l).

Section 9-3


• Gases that are commonly produced are carbon dioxide, hydrogen cyanide, and hydrogen sulfide.

2HI(aq) + Li2S(aq) → H2S(g) + 2LiI(aq)

A. A

B. B

C. C

D. D

Section 9-3

A B C D

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What is the solvent in an aqueous solution?

A. hydrogen

B. sodium ions

C. water

D. alcohol

A. A

B. B

C. C

D. D

Section 9-3


A B C D

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An equation that includes only the particles that participate in a reaction is called:

A. net ionic equation

B. spectator ions

C. complete ionic equation

D. reduced ionic equation

Study Guide 1

Section 9.1 Reactions and Equations

Key Concepts

• Some physical changes are evidence that indicate a chemical reaction has occurred.

• Word equations and skeleton equations provide important information about a chemical reaction.

• A chemical equation gives the identities and relative amounts of the reactants and products that are involved in a chemical reaction.

• Balancing an equation involves adjusting the coefficients until the number of atoms of each element is equal on both sides of the equation.

Study Guide 2

Section 9.2 Classifying Chemical Reactions

Key Concepts

• Classifying chemical reactions makes them easier to understand, remember, and recognize.

• Activity series of metals and halogens can be used to predict if single-replacement reactions will occur.

Study Guide 3

Section 9.3 Reactions in Aqueous Solutions

Key Concepts

• In aqueous solutions, the solvent is always water. There are many possible solutes.

• Many molecular compounds form ions when they dissolve in water. When some ionic compounds dissolve in water, their ions separate.

• When two aqueous solutions that contain ions as solutes are combined, the ions might react with one another. The solvent molecules do not usually react.

• Reactions that occur in aqueous solutions are double-replacement reactions.

A. A

B. B

C. C

D. D

Chapter Assessment 1

A B C D

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The law of conservation of mass requires what in a chemical reaction equation?

A. both sides of the equation to contain the same substances

B. the reactants to have the same amount of molecules as the products

C. both sides to have the same amount of atoms of each element

D. the products to have fewer molecules than the reactants

A. A

B. B

C. C

D. D


A B C D

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A reaction that gives off heat is what type of reaction?

A. single replacement reaction

B. double replacement reaction

C. synthesis reaction

D. combustion reaction

A. A

B. B

C. C

D. D


A B C D

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Ions that are present in a solution and do not participate in a chemical reaction when another substance is added are called ____.

A. spectator ions

B. reactants

C. products

D. net ions

A. A

B. B

C. C

D. D


A B C D

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A double replacement reaction produces all of the following except ____.

A. gases

B. solids

C. light

D. water

A. A

B. B

C. C

D. D


A B C D

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What type of reaction is the following?

2H2O(l) + energy → H2(g) + O2(g)

A. synthesis reaction

B. decomposition reaction

C. combustion reaction

D. replacement reaction

A. A

B. B

C. C

D. D

STP 1

A B C D

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What type of reaction is the following?

2H2(g) + O2(g) → 2H2O(l)

A. replacement reaction

B. synthesis

C. combustion reaction

D. double replacement reaction

A. A

B. B

C. C

D. D

STP 2

A B C D

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A precipitate forms in a double replacement reaction only if:

A. the reactivities of the compounds differ

B. the new compound is denser than water

C. the new compound is soluble in water

D. the new compound is not soluble in water

A. A

B. B

C. C

D. D

STP 3

A B C D

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A ____ is a statement that uses chemical formulas to show the identities and relative amounts of the substances involved in a chemical reaction.

A. word equation

B. skeleton equation

C. chemical equation

D. balanced equation

A. A

B. B

C. C

D. D

STP 4

A B C D

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Predict the type of reaction.

LiBr2 (aq) + 2NaOH (aq) → ____

A. synthesis reaction

B. combustion reaction

C. single replacement reaction

D. double replacement reaction

A. A

B. B

C. C

D. D

STP 5

A B C D

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Which reactions are essentially the opposite of synthesis reactions?

A. single-replacement

B. decomposition

C. combustion

D. double-replacement

chapter 9 honors

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