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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