Chapter 8Chapter 8

Chemical Chemical Equations Equations and and ReactionsReactions

8-1 Describing Chemical Reactions8-1 Describing Chemical Reactions

Chemical reaction – process by which one Chemical reaction – process by which one or more substances are changed into one or more substances are changed into one or more different substancesor more different substances

Reactants – starting substancesReactants – starting substancesProducts – ending substancesProducts – ending substancesConservation of mass tells us that the Conservation of mass tells us that the

mass of the reactants must be equal to the mass of the reactants must be equal to the mass of the productsmass of the products

8-1 Chemical Equations8-1 Chemical Equations Chemical equation – represents (with symbols and Chemical equation – represents (with symbols and

formulas) the identities and relative amounts of the formulas) the identities and relative amounts of the reactants and products in a chemical reactionreactants and products in a chemical reaction

8-1 Signs of a Chemical Reaction8-1 Signs of a Chemical Reaction

Evolution of heat and lightEvolution of heat and light Production of a Production of a

gas/bubblesgas/bubbles Formation of a precipitateFormation of a precipitate Color changeColor change

8-1 Requirements for Properly 8-1 Requirements for Properly Written Chemical EquationsWritten Chemical Equations

All reactants and products must be All reactants and products must be representedrepresented

Correct symbols and formulas must be Correct symbols and formulas must be used for all substances in the equation used for all substances in the equation (remember diatomics!)(remember diatomics!)

Reactants on left, products on rightReactants on left, products on rightArrow means “yields” or “forms”Arrow means “yields” or “forms”Law of conservation of matter must be Law of conservation of matter must be

satisfied – equations must be BALANCEDsatisfied – equations must be BALANCED

8-1 Balancing Chemical Equations8-1 Balancing Chemical Equations

Equations must be balanced to show the Equations must be balanced to show the same number of atoms of each type on same number of atoms of each type on both sides of the equationboth sides of the equation

Balance equations by writing coefficientsBalance equations by writing coefficientsCoefficient – a small whole number that Coefficient – a small whole number that

appears in front of a formula in a chemical appears in front of a formula in a chemical equationequation

NEVER change subscripts!NEVER change subscripts!

8-1 Balancing Equations8-1 Balancing Equations

Write a balanced chemical equation for the Write a balanced chemical equation for the formation of ammonia from its elements. formation of ammonia from its elements.

8-1 Balancing Chemical Equations8-1 Balancing Chemical Equations

Write a balanced chemical equation for the Write a balanced chemical equation for the decomposition of sodium chloride to its decomposition of sodium chloride to its elements. elements.

8-1 Word and Formula Equations8-1 Word and Formula Equations

It is often helpful to begin by writing a word It is often helpful to begin by writing a word equation that represents all the facts about equation that represents all the facts about a chemical reaction. a chemical reaction.

In a word equation, reactants and products In a word equation, reactants and products are represented by words.are represented by words.

methane + oxygen methane + oxygen carbon dioxide + water carbon dioxide + water

8-1 Word and Formula Equations8-1 Word and Formula Equations

A formula equation represents the A formula equation represents the reactants and products of a chemical reactants and products of a chemical reaction by their symbols or formulas.reaction by their symbols or formulas.

CHCH44 + O + O22 CO CO22 + H + H22O (unbalanced)O (unbalanced)

8-1 Additional Symbols Used in 8-1 Additional Symbols Used in Chemical EquationsChemical Equations

(s)(s)

(l)(l)

(aq)(aq)

(g)(g)

YieldsYields

SolidSolid

LiquidLiquid

AqueousAqueous

gasgas

8-1 Reversible Reactions8-1 Reversible Reactions

A reversible reaction is one in which A reversible reaction is one in which products can re-form the original reactantsproducts can re-form the original reactants

3Fe(s) + 4H3Fe(s) + 4H22O(g) FeO(g) Fe33OO44(s) + 4H(s) + 4H22(g)(g)

8-1 Reactions Requiring Heat8-1 Reactions Requiring Heat

Some reactions will only Some reactions will only proceed if the reactants proceed if the reactants are heated. are heated.

2HgO(s) 2HgO(s) 2Hg(l) + O 2Hg(l) + O22(g)(g)

8-1 Practice8-1 Practice

Translate the following into a sentence:Translate the following into a sentence:

2NaOH(aq) + MgCl2NaOH(aq) + MgCl22(aq) (aq) 2NaCl(aq) + Mg(OH) 2NaCl(aq) + Mg(OH)22(s)(s)

NaCl(aq) + AgNONaCl(aq) + AgNO33(aq) (aq) NaNO NaNO33(aq) + AgCl(s)(aq) + AgCl(s)

8-1 Practice8-1 Practice

Write a balanced chemical equation for the Write a balanced chemical equation for the following processes:following processes:

Solid calcium reacts with solid sulfur to Solid calcium reacts with solid sulfur to produce solid calcium sulfide.produce solid calcium sulfide.

Hydrogen gas reacts with fluorine gas to Hydrogen gas reacts with fluorine gas to produce hydrogen fluoride gas. produce hydrogen fluoride gas.

8-2 Types of Chemical Reactions 8-2 Types of Chemical Reactions

Using generalizations about the ways Using generalizations about the ways various substances interact with each various substances interact with each other, we can predict the products of other, we can predict the products of reactionsreactions

There are five main types of chemical There are five main types of chemical reactions. reactions.

8-2 Types of Chemical Reactions8-2 Types of Chemical Reactions

SynthesisSynthesisDecompositionDecompositionSingle replacementSingle replacementDouble replacementDouble replacementCombustion (of hydrocarbons)Combustion (of hydrocarbons)

8-2 Synthesis Reactions8-2 Synthesis Reactions

Two or more substances react to form one Two or more substances react to form one new compoundnew compound

A + X A + X AX AX

Recognize by SINGLE PRODUCTRecognize by SINGLE PRODUCT

8-2 Synthesis Reactions8-2 Synthesis Reactions

Reactions of elements with oxygen or Reactions of elements with oxygen or sulfur FORM OXIDES OR SULFIDESsulfur FORM OXIDES OR SULFIDES

Magnesium reacts with oxygenMagnesium reacts with oxygen

Barium reacts with sulfurBarium reacts with sulfur

Rubidium reacts with sulfurRubidium reacts with sulfur

8-2 Synthesis Reactions8-2 Synthesis Reactions

Reactions of metals with halogens FORM Reactions of metals with halogens FORM METAL HALIDESMETAL HALIDES

Sodium reacts with chlorineSodium reacts with chlorine

Potassium reacts with iodinePotassium reacts with iodine

Magnesium reacts with fluorineMagnesium reacts with fluorine

8-2 Synthesis Reactions8-2 Synthesis Reactions

Metal oxides react with water to form Metal oxides react with water to form metal hydroxidesmetal hydroxides

Calcium oxide reacts with waterCalcium oxide reacts with water

Magnesium oxide reacts with waterMagnesium oxide reacts with water

8-2 Synthesis Reactions8-2 Synthesis Reactions

Nonmetal oxides react with water to form Nonmetal oxides react with water to form acidsacids

Sulfur dioxide reacts with waterSulfur dioxide reacts with water

Carbon dioxide reacts with waterCarbon dioxide reacts with water

8-2 Decomposition Reactions8-2 Decomposition Reactions

A single compound breaks down to A single compound breaks down to produce two or more simpler substancesproduce two or more simpler substances

AX AX A + X A + X

Recognize by single reactantRecognize by single reactant

Often require energy in the form of heat, Often require energy in the form of heat, light or electricity.light or electricity.

8-2 Decomposition Reactions8-2 Decomposition Reactions

Decomposition of binary compounds Decomposition of binary compounds produces elementsproduces elements

Decomposition of waterDecomposition of water

Decomposition of sodium chlorideDecomposition of sodium chloride

Decomposition of magnesium mercury (II) Decomposition of magnesium mercury (II) oxideoxide

8-2 Decomposition Reactions8-2 Decomposition Reactions

Decomposition of metal carbonates Decomposition of metal carbonates FORMS METAL OXIDE AND CARBON FORMS METAL OXIDE AND CARBON DIOXIDEDIOXIDE

Decomposition of calcium carbonateDecomposition of calcium carbonate

Decomposition of magnesium carbonateDecomposition of magnesium carbonate

8-2 Decomposition Reactions8-2 Decomposition Reactions

Decomposition of metal hydroxides Decomposition of metal hydroxides FORMS METAL OXIDES AND WATERFORMS METAL OXIDES AND WATER

Decomposition of calcium hydroxideDecomposition of calcium hydroxide

Decomposition of copper (II) hydroxideDecomposition of copper (II) hydroxide

8-2 Decomposition Reactions8-2 Decomposition Reactions

Decomposition of metal chlorates FORMS Decomposition of metal chlorates FORMS METAL CHLORIDES AND OXYGENMETAL CHLORIDES AND OXYGEN

Decomposition of potassium chlorateDecomposition of potassium chlorate

Decomposition of sodium chlorateDecomposition of sodium chlorate

8-2 Decomposition Reactions8-2 Decomposition Reactions

Decomposition of acids PRODUCES Decomposition of acids PRODUCES NONMETAL OXIDES AND WATERNONMETAL OXIDES AND WATER

Decomposition of carbonic acidDecomposition of carbonic acid

Decomposition of sulfuric acidDecomposition of sulfuric acid

8-2 Single Replacement Reactions8-2 Single Replacement Reactions

One element replaces another similar One element replaces another similar element in a compoundelement in a compound

A + BX A + BX AX + B AX + B

OROR

Y + BX Y + BX BY + X BY + X

8-2 Single Replacement Reactions8-2 Single Replacement Reactions

Replacement of a metal by another metalReplacement of a metal by another metalAluminum reacts with lead nitrateAluminum reacts with lead nitrate

Sodium reacts with iron (II) chlorideSodium reacts with iron (II) chloride

Calcium reacts with aluminum phosphateCalcium reacts with aluminum phosphate

8-2 Single Replacement Reactions8-2 Single Replacement Reactions

Replacement of hydrogen by a metalReplacement of hydrogen by a metalSodium reacts with waterSodium reacts with water

Magnesium reacts with hydrochloric acidMagnesium reacts with hydrochloric acid

Calcium reacts with nitric acidCalcium reacts with nitric acid

8-2 Single Replacement Reactions8-2 Single Replacement Reactions

Replacement of HalogensReplacement of HalogensChlorine reacts with potassium bromideChlorine reacts with potassium bromide

Fluorine reacts with sodium chlorideFluorine reacts with sodium chloride

Fluorine reacts with potassium iodideFluorine reacts with potassium iodide

8-3 Activity Series of the Elements8-3 Activity Series of the Elements

An activity series is a list of elements organized An activity series is a list of elements organized according to the ease with which the elements according to the ease with which the elements undergo certain chemical reactionsundergo certain chemical reactions

For metals, greater activity means greater ease For metals, greater activity means greater ease of LOSS OF ELECTRONS to form cations.of LOSS OF ELECTRONS to form cations.

For nonmetals, greater activity means greater For nonmetals, greater activity means greater ease of GAIN OF ELECTRONS to form anions.ease of GAIN OF ELECTRONS to form anions.

An activity series can be used to determine An activity series can be used to determine whether or not a single replacement reaction will whether or not a single replacement reaction will take place. take place.

8-3 Activity Series8-3 Activity Series

More active metals are More active metals are HIGHER on the list.HIGHER on the list.

A more active metal can A more active metal can replace a less active replace a less active metal on the activity metal on the activity series. series.

Example: Na + CoClExample: Na + CoCl22 Example: Cu + AlClExample: Cu + AlCl33 Example: Cr + HCl Example: Cr + HCl Example: Au + MgSOExample: Au + MgSO44

8-3 Activity Series8-3 Activity Series

Example: ClExample: Cl22 + NaBr + NaBr Example: BrExample: Br22 + KF + KF Example: ClExample: Cl22 + MgBr + MgBr22

8-2 Double Replacement Reactions8-2 Double Replacement Reactions

The ions of two compounds exchange The ions of two compounds exchange places to form two new compoundsplaces to form two new compounds

One of the products is usually a One of the products is usually a precipitate, gas or molecular compound precipitate, gas or molecular compound (like water)(like water)

AX + BY AX + BY AY + BX AY + BX

8-2 Double Replacement Reactions8-2 Double Replacement Reactions

Formation of a precipitateFormation of a precipitatePotassium iodide reacts with lead (II) Potassium iodide reacts with lead (II)

nitratenitrate

Magnesium chloride reacts with sodium Magnesium chloride reacts with sodium hydroxidehydroxide

8-2 Double Replacement Reactions8-2 Double Replacement Reactions

Formation of a gasFormation of a gas Iron (II) sulfide reacts with hydrochloric Iron (II) sulfide reacts with hydrochloric

acidacid

8-2 Double Replacement Reactions8-2 Double Replacement Reactions

Formation of waterFormation of waterAn acid reacts with a base – also called a An acid reacts with a base – also called a

NEUTRALIZATION reactionNEUTRALIZATION reactionHydrochloric acid reacts with sodium Hydrochloric acid reacts with sodium

hydroxidehydroxide

Sulfuric acid reacts with potassium Sulfuric acid reacts with potassium hydroxidehydroxide

8-2 Combustion Reactions8-2 Combustion Reactions

A substance combines with oxygen, A substance combines with oxygen, releasing a large amount of energy in the releasing a large amount of energy in the form of light and heatform of light and heat

Hydrocarbons burn in oxygenHydrocarbons burn in oxygenA hydrocarbon is a compound composed A hydrocarbon is a compound composed

of hydrogen and carbonof hydrogen and carbon

8-2 Combustion Reactions8-2 Combustion Reactions

Combustion of hydrocarbonsCombustion of hydrocarbonsWhen a hydrocarbon reacts with oxygen, When a hydrocarbon reacts with oxygen,

the products are carbon dioxide and waterthe products are carbon dioxide and waterCombustion of butaneCombustion of butane

Combustion of heptaneCombustion of heptane

8-2 Simple Hydrocarbons (C8-2 Simple Hydrocarbons (CnnHH2n+22n+2))

CHCH44

CC22HH66

CC33HH88

CC44HH1010

CC55HH1212

CC66HH1414

CC77HH1616

CC88HH1818

CC99HH2020

CC1010HH2222

methanemethane ethaneethane propanepropane butanebutane pentanepentane hexanehexane heptaneheptane octaneoctane nonanenonane decanedecane

It’s over!It’s over!