Chapter 10: Chapter 10: Chemical ReactionsChemical Reactions

Chemical ReactionsChemical Reactions

Defn – process by which the atoms of one Defn – process by which the atoms of one or more substances are rearrangedor more substances are rearranged

- new substances are formed- new substances are formed

Evidences of a chemical reactionEvidences of a chemical reaction

1) gas production1) gas production

2) light production2) light production

3) temperature change (endo/exothermic)3) temperature change (endo/exothermic)

4) precipitate formed (solid from 2 liquids)4) precipitate formed (solid from 2 liquids)

5) permanent color change5) permanent color change

Energy is stored in compounds as chemical Energy is stored in compounds as chemical potential energy due to specific arrangements potential energy due to specific arrangements of atoms. A chemical reaction changes the of atoms. A chemical reaction changes the potential energy present. When energy is lost potential energy present. When energy is lost as heat, it is called a __________________. as heat, it is called a __________________. These reactions get hotter. Sometimes energy These reactions get hotter. Sometimes energy is gained; heat is added for a reaction to occur. is gained; heat is added for a reaction to occur. These are called ______________________, These are called ______________________, which get colder.which get colder.

exothermic reaction

endothermic reaction

Word EquationWord Equation

Defn – equation expressed in wordsDefn – equation expressed in words

Iron + chlorine iron (III) chloride

Formula EquationFormula Equation

Defn – equation with chemical formulasDefn – equation with chemical formulas

Coefficients – whole # placed in front of Coefficients – whole # placed in front of compoundcompound Balances the number of atomsBalances the number of atoms

2 Fe + 3 Cl2 2 FeCl3

Parts Of A ReactionParts Of A Reaction

SymbolsSymbols

(s)

(l)

(g)

(aq)

solid

liquid

gas

aqueous (dissolved in water)

Δ heat added

exampleexample

Solid calcium carbonate reacts with a solution Solid calcium carbonate reacts with a solution of hydrochloric acid to produce aqueous of hydrochloric acid to produce aqueous calcium chloride, gaseous carbon dioxide, and calcium chloride, gaseous carbon dioxide, and liquid waterliquid water

CaCO3 (s) + HCl (aq) CaCl2 (aq)

+ CO2 (g) + H2O (l)

Diatomic ElementsDiatomic Elements

Defn – 7 elements that NEVER occur as Defn – 7 elements that NEVER occur as singular atoms (singular atoms (always paired with an always paired with an the same or different elementthe same or different element))

HH22 O O22 F F22 Br Br22 I I22 N N22 Cl Cl22

Ex: 2 HCl + K 2 KCl + H2

Balancing EquationsBalancing Equations

Number of reactant atoms on left of an Number of reactant atoms on left of an element must equal number of product element must equal number of product atoms on the rightatoms on the right

Must obey Must obey law of conservation of masslaw of conservation of mass

Rules for balancing equationsRules for balancing equations

1) 1) Only coefficientsOnly coefficients are changed in are changed in balancing reactionsbalancing reactions

2) Never change subscript during balancing2) Never change subscript during balancing

3) Coefficients are placed in front of 3) Coefficients are placed in front of compound and multiplied across compound and multiplied across compound to get total # of atoms of each compound to get total # of atoms of each elementelement

Helpful HintsHelpful Hints

Balance hydrogen and oxygen lastBalance hydrogen and oxygen last

Balance polyatomic ions as a group if Balance polyatomic ions as a group if present on both reactants and productspresent on both reactants and products

BeforeBefore

AfterAfter

MgCl2 + NaOH Mg(OH)2 + NaCl

1 Mg 1 Mg

2 Cl 1 Cl1 Na 1 Na

1 OH 2 OH

MgCl2 + 2 NaOH Mg(OH)2 + 2 NaCl

1 Mg 1 Mg

2 Cl 2 Cl2 Na 2 Na

2 (OH) 2 (OH)

Sample ProblemsSample Problems

sodium and chlorine combine to form sodium and chlorine combine to form sodium chloridesodium chloride

NaNa ++ ClCl22 NaClNaCl11 2222

Sample ProblemsSample Problems

sodium hydroxide and calcium bromide sodium hydroxide and calcium bromide react to produce calcium hydroxide and react to produce calcium hydroxide and sodium bromidesodium bromide

NaOHNaOH CaBrCaBr22

Ca(OH)Ca(OH)22 NaBrNaBr

++

++

22

22

11

11

Sample ProblemsSample Problems

aluminum sulfate and calcium hydroxide aluminum sulfate and calcium hydroxide produce calcium sulfate and aluminum produce calcium sulfate and aluminum hydroxidehydroxide

AlAl22(SO(SO44))33 Ca(OH)Ca(OH)22

CaSOCaSO44 Al(OH)Al(OH)33

++

++

11

22

33

33

Classifying Chemical ReactionsClassifying Chemical Reactions

SynthesisSynthesis DecompositionDecomposition Single replacementSingle replacement Double ReplacementDouble Replacement CombustionCombustion

SynthesisSynthesis

Defn – two or more substances react Defn – two or more substances react to form ONE productto form ONE product

A + B A + B AB AB

Hey baby let’s get jiggy.

SynthesisSynthesis

reaction of two elementsreaction of two elements

___Al + ___Cl2 ___AlCl3

Al3+ Cl1-

22 2233

DecompositionDecomposition

defn – one substance breaks down defn – one substance breaks down into two or more simpler productsinto two or more simpler products

AB AB A + B A + B

Break yoself fool!

DecompositionDecomposition

Ex reactionEx reaction

__ NaN3 (s) ___ Na (s) + ___ N2 (g)2 2 3

__ CaO (s) ___ Ca (s) + ___ O2 (g)2 2 1

Single Replacement ReactionsSingle Replacement Reactions

Defn – one element replaces another Defn – one element replaces another element in a compound to form element in a compound to form new compoundnew compound

A + BX A + BX AX + BAX + B

I’m gon’ dance with yo’ lady

Reactivity SeriesReactivity Series

metalsmetals

halogenshalogens

Li K Ca Na Mg Al Mn Zn Fe Ni Sn Pb Cu Ag Au

most active least active

F Cl Br IF Cl Br I

most active least active

examplesexamples

aluminum + iron (III) oxidealuminum + iron (III) oxide

Al Fe2O3+

Stronger?

Al3+ O2-

Al2O3Fe +

Fe3+ O2-

2 21 1

examplesexamples

silver + copper (I) nitratesilver + copper (I) nitrate

Ag CuNO3+

Stronger?

Cu1+ NO31-

NO RXN

examplesexamples

fluorine gas + sodium bromidefluorine gas + sodium bromide

F2 NaBr+

Stronger?

Br2NaF +

Na1+ F1-

221 1

examplesexamples

chlorine gas + hydrogen fluoridechlorine gas + hydrogen fluoride

Cl2 HF+

Stronger?

NO RXN

Double ReplacementDouble Replacement

Defn – exchange of Defn – exchange of cationscations between two between two ionic compoundsionic compounds

A B + C D AD + CBswitch

3 possible products of double 3 possible products of double replacement rxnsreplacement rxns

PrecipitatePrecipitate GasGas WaterWater

Ex problemEx problem

lithium iodide and aqueous silver nitrate lithium iodide and aqueous silver nitrate reactreact

Li1+ I1- Ag1+ NO31-

Li I AgNO3 LiNO3Ag I (s)+ +

CombustionCombustion

defn – compound reacts with Odefn – compound reacts with O22

HydrocarbonHydrocarbon – cmpd w/ only carbon – cmpd w/ only carbon and hydrogenand hydrogen

CombustionCombustion

Combustion of hydrocarbonsCombustion of hydrocarbons

ALWAYS produces ALWAYS produces COCO22 and and HH22OO

CxHy + O2 CO2 + H2O

Ex problemEx problem

show combustion of propane (Cshow combustion of propane (C33HH88) gas) gas

C3H8 O2 CO2 H2O+ +1 5 3 4