Types of ReactionsTypes of ReactionsChemistryChemistry

Learning Objective

TLW identify and quantify changes that occur during chemical reactions (TEKS 8)

Agenda

Review of Basics Define Types of Chemical Reactions and

Real-World Examples Examples of the Types of Chemical

Reactions Group Practice Individual Practice Labs

Chemical Reactions –General Stuff

Reactants are added together to make products

Reactants are found on left side of chemical equation and products are on the right side

Compounds are formed – substances made up of two or more elements that chemically combined (not easily separated or impossible to return to original element)

Chemical Reactions –General Stuff

Valence electrons and periodic trends determine how various atoms of elements react (or don’t react)

Catalysts are “outside agents” that may be added to speed up reactions or cause reactions to perform differently under different conditions (such as varying temperatures).– They are not used up in the reaction

Chemical Reactions –General Stuff

Don’t forget about the laws of conservation of mass and energy… neither can be created nor destroyed– Reactants are transformed– Products are formed– Chemical energy converts to heat, light,

electricity, sound

Chemical Reactions –General Stuff

Also – Law of Definite Proportions, which states in any sample of a chemical compound the elements are always combined in the same proportion by mass

H2O

H = 1 g x 2 = 2 g

O = 16 g

Total 18 g

H = 2 g / 18 g = 11% O = 16 g / 18 g = 89%

Chemical Reactions –General Stuff

From Dalton’s Laws (remember him?) Law of Multiple Proportions states

whenever two elements form more than one compound different masses of one element that combine with the same mass of the other element are in the ratio of small whole number

H2O H2O2

Chemical Reactions –General Stuff

Law of Definite Proportions – describes composition of one compound

Law of Multiple Proportions – compares composition of two different compounds containing same elements

Types of Reactions Combination Combination (a.k.a. Synthesis, Addition)(a.k.a. Synthesis, Addition) DecompositionDecomposition Single Replacement Single Replacement (a.k.a. Single Displacement)(a.k.a. Single Displacement) Double Replacement Double Replacement (a.k.a. Double (a.k.a. Double

Displacement)Displacement) CombustionCombustion NeutralizationNeutralization PrecipitationPrecipitation Reduction/Oxidation Reactions (Reduction/Oxidation Reactions (RedoxRedox)) Energy Producing – Exothermic, Endothermic, Energy Producing – Exothermic, Endothermic,

LightLight

CombinationCombination(aka Synthesis, Addition)(aka Synthesis, Addition)

Two or more elements or substances combine Two or more elements or substances combine to form a new compound. to form a new compound.

A + B A + B AB AB Examples –Examples –

– Formation of rustFormation of rust– Air pollutant sulfur dioxideAir pollutant sulfur dioxide– Polymerization (plastics)Polymerization (plastics)– PhotoPhotosynthesissynthesis (plants) (plants)

CombinationCombination A + B A + B AB AB Where A and B are elements Where A and B are elements

and AB is a compound and AB is a compound Note that only one compound Note that only one compound

exists on the exists on the RIGHTRIGHT SIDE… SIDE…

CombinationCombination

4Fe(s) + 3O4Fe(s) + 3O22(g) (g) 2Fe 2Fe22OO33(s)(s) S(s) + OS(s) + O22(g) (g) SO SOxx(g)(g) 2Na + Cl2Na + Cl22 2NaCl 2NaCl

ExamplesExamples

Teacher Demo – need a better one…..

DecompositionDecomposition

A single compound is broken down A single compound is broken down to produce two or more smaller to produce two or more smaller compounds and/or elements.compounds and/or elements.

AB AB A + B A + B Example – Example –

– Water with electricity into Water with electricity into hydrogen and oxygen (electrolysis)hydrogen and oxygen (electrolysis)

– Baking soda with heatBaking soda with heat

DecompositionDecomposition

AB AB A + B A + B Where AB is a compound and Where AB is a compound and

A & B are elements or other A & B are elements or other compoundscompounds

Note that only one compound Note that only one compound exists on the exists on the LEFTLEFT SIDE… SIDE…

DecompositionDecomposition

Examples:Examples:

2H2H22OO(l)(l) 2H 2H2(g)2(g) + O + O2(g) 2(g)

NaHCONaHCO3(s)3(s) 2H 2H2(g)2(g) + NaCO + NaCO33heat

Teacher demo – baking soda and heat

Single ReplacementSingle Replacement(Single Displacement)(Single Displacement)

One element replaces (displaces) a similar One element replaces (displaces) a similar element in a compoundelement in a compound

Produces heat (is exothermic)Produces heat (is exothermic) A + BC A + BC AC + B AC + B Example – Example –

– If you place an iron nail into a beaker of If you place an iron nail into a beaker of copper (II) chloride you will begin to see copper (II) chloride you will begin to see reddish copper forming on the iron.reddish copper forming on the iron.

– Iron Iron replacesreplaces ( (displacesdisplaces)) copper in the copper in the solution and the copper falls out of solution solution and the copper falls out of solution as a metalas a metal

Single ReplacementSingle Replacement A + BC A + BC AC + B AC + B Where A and B are elements and BC Where A and B are elements and BC

and AC are compoundsand AC are compounds Can have more than 2 reactants and/or Can have more than 2 reactants and/or

productsproducts

Example: Example: 2HCl2HCl(l)(l) + Zn + Zn(s)(s) ZnCl ZnCl2(l)2(l) + H + H2(g)2(g)

FeFe(s) (s) + CuCl + CuCl2(l)2(l) Cu Cu(s)(s) + FeCl + FeCl2(l)2(l)

Single ReplacementSingle Replacement All single replacement reactions are All single replacement reactions are

exothermicexothermic They give off heat and occur rapidlyThey give off heat and occur rapidly

Teacher demo – Zinc plus hydrochloric acid or iron nail in copper(II)chloride

Double ReplacementDouble Replacement(Double Displacement)(Double Displacement)

Ions from two compounds in solution exchange Ions from two compounds in solution exchange to produce two new compoundsto produce two new compounds

AB + CD AB + CD AD + CB AD + CB One compound usually forms a precipitate that One compound usually forms a precipitate that

settles out of the solution, a gas that bubbles settles out of the solution, a gas that bubbles out, or a molecular compound like waterout, or a molecular compound like water

The other compound formed often remains The other compound formed often remains dissolved in the solutiondissolved in the solution

Examples – Examples – – Baking soda and vinegarBaking soda and vinegar– Dried fruitDried fruit

Double ReplacementDouble Replacement AB + CD AB + CD AD + CB AD + CB Where AB, CD, AD, & CB are all Where AB, CD, AD, & CB are all

compoundscompounds Can have more than 2 reactants and/or Can have more than 2 reactants and/or

productsproducts Examples:Examples: 2HCl + 2NaOH 2HCl + 2NaOH 2NaCl + 2H2NaCl + 2H22OO

NaNa22SOSO3(aq)3(aq) + 2HCl + 2HCl(aq)(aq)

2NaCl2NaCl(aq)(aq) + H + H22OO(l)(l) + SO + SO2(g)2(g)

Teacher demo – the ever popular baking soda and vinegar or cleaning pennies with vinegar using salt as a catalyst

CombustionCombustionCarbon substances combine with oxygen, Carbon substances combine with oxygen, releasing large amounts of energy, in releasing large amounts of energy, in the form of heat, light, etc. Carbon the form of heat, light, etc. Carbon dioxide and water are also typical dioxide and water are also typical productsproducts

CCxxHHyy + O + O22 CO CO22 + H + H22OO

Examples –Examples –– Natural gas to heat a houseNatural gas to heat a house– Hydrogen powered carsHydrogen powered cars

General FormulaGeneral Formula

CCxxHHyy + O + O22 CO CO22 + H + H22OOhydrocarbon oxygen carbon waterhydrocarbon oxygen carbon water

dioxidedioxide

Examples -Examples -

CHCH4 4 + 2O+ 2O22 COCO22 + 2H + 2H22OO

2H2H22(g) + O(g) + O22(g) (g) 2H 2H22O(l)O(l)

Teacher demo – lighting a match

NeutralizationNeutralization Double Replacement Reaction where wn acid

and a base react to form water and a salt General formula

HA + BOH H2O + BA acid base water salt

Examples –

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

H2SO4(aq) + Ca(OH)2(aq) H2O(l) + CaSO4(s)

PrecipitationPrecipitation When solutions are saturated, adding

additional ions will cause a precipitate to form Solid – usually sinks to bottom, but can float Solubility product (Ksp) can be used to predict

formation of precipitates– If ion-product concentration > Ksp then a precipitate

will form

– If ion-product concentration < Ksp then a precipitate will not form

Teacher demo – baking soda and vinegar… again (how boring)

Practice Worksheet – Identify 5 basic reactions

Discovery Video - ElectrochemistryReduction/Oxidation Reactions

A. Reaction in which electrons are transferredB. Commonly called the redox reactionC. One element is reduced – it gains electrons

One element is oxidized – it loses electrons

Reduction/OxidationReduction/Oxidation

Redox reactions have radicals fragments of molecules with at least one electron for bonding

Ex. of radicals = Styrofoam

Example of redox reactionRust = iron reacts with oxygen

Fe2O3

Fe loses 3 electronsO gains 2 electrons

Rules for Assigning Oxidation Numbers

Rule 1

The oxidation number of any uncombined element is 0

Example:

The oxidation number of Na (s) is 0.

Rule 2

The oxidation number of a monatomic ion equals the charge on the ion.

Example:

The oxidation number of Cl- is -1.

Rule 3

The more electronegative element in a binary compound is assigned the number equal to the charge it would have if it were an ion.

Example:

The oxidation number of O in NO is -2.

Rule 4

The oxidation number of fluorine in a compound is always -1.

Example:

The oxidation number of F in LiF is -1.

Rule 5

Oxygen has an oxidation number of -2 unless it is combined with F, when it is +2, or it is in a peroxide, such as H2O2, when it is -1.

Example:

The oxidation number of O in NO2 is -2.

Rule 6

The oxidation state of hydrogen in most of its compounds is +1 unless it is combined with a metal, in which case it is -1.

Example:

The oxidation number of H in LiH is -1.

Rule 7

In compounds, Group 1 and 2 elements and aluminum have oxidation numbers of +1, +2, and +3, respectively.

Example:

The oxidation number of Ca in CaCO3 is +2.

Rule 8

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

Example:

The oxidation number of

C in CCO3 is +4.

Rule 9

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

Example:

The oxidation number of P in H2PO- 4 is +5.

Exothermic Reactions

In many reactions, less energy is required to break the bonds in the reactants than is released when bonds form to make new products

In these reactions some type of heat or light is released and they are called exothermic

Exothermic reactions can be detected by a rise in temperature

Exothermic Reactions

What are examples of exothermic reactions you are familiar with?

Demonstration

Endothermic Reactions

Sometimes more energy is required to break bonds in the reactants than is released to form new products

The are called endothermic reactions You can detect these reactions by a

decrease in temperature

Endothermic Reactions

What are examples of endothermic reactions you are familiar with?

Demonstration

Group Practice ~ Name Those Reactions

A Group Activity

Types of Chemical Reactions – Sorting Matslink

Individual Practice

Identifying Types of Reactions Worksheet link

Crossword Puzzle

Looking Ahead Labs –

– Conservation of Mass– Types of Chemical Reactions– Empirical Formula Determination– Predicting the Amount of Product in a Reaction– Identifying Relationships between Reactants and

Products in a Reaction– Predicting the Products of a Reaction– Precipitation Reactions– Energetic Reactions – exothermic and endothermic

experiments– Qualitative and Quantitative Analysis

More on calculating definite proportions and multiple proportions