LEAVING
CERTIFICATE
CHEMISTRY
NOTES
2016/2017
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CianHurley
PART A
QUESTION
EXPERIMENT
PAGE
Question 1
Titrations
1
Question 2
Organic chemistry experiments
15
Question 3
Other experiments
26
PART B
UNIT
PAGE
1 – Periodic table and atomic
The periodic table
39
structure
The Atomic structure
42
Radioactivity
46
Electronic structure of atoms
49
Oxidation and reduction
52
2.1
Chemical compounds
55
2.2
Ionic bonding
56
2.3
Covalent bonding
58
2.4
Electronegativity
60
2.5
Shapes of molecules and intermolecular forces
60
2.6
Oxidation numbers
64
3.1
States of matter
67
3.2
Gas laws
67
3.3
The mole
69
3.4
Chemical formulae
70
3.5
Chemical equations
71
4.1
Concentration of solutions
73
4.2
Acids and bases
74
5.1
Sources of hydrocarbons
78
5.2
Structure of aliphatic carbons
78
5.3
Aromatic hydrocarbons
83
5.4
Exothermic and endothermic reactions
83
5.5
Oil and its refining prodcuts
85
5.6
Other chemical fuels
89
2 – Chemical bonding
3 – Stoichiometry
4 – Volumetric Analysis
5 – Fuels and heats of reaction
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Leaving Certificate Chemistry Notes 2016/2017
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6 – Rates of reaction
7 – Organic chemistry
8 – Chemical Equilibrium
9 – Environmental chemistry: water
6.1
Reaction rates
90
6.2
Factors affecting rates of reaction
90
7.1
Tetrahedral carbon
95
7.2
Planar carbon
99
7.3
Organic chemical reaction types
106
7.4
Organic natural products
117
8.1
Chemical equilibrium
118
8.2
Le Chatelier’s principle
120
9.1
pH scale
122
9.2
Hardness in water
126
9.3
Water treatment
127
9.4
Water analysis
130
These notes are compiled based on the State Examinations Commission (SEC) syllabus with reference
to teacher guidelines. All areas covered correlate with past exam papers (including 1990s) and some
sample pre/mock papers. The “higher order questions” are designed to anticipate future questions
which bring together multiple parts of the course to test understanding and reasoning. Marking
schemes are also linked in to relevant parts with special attention on common student mistakes and
how to achieve full marks in each question.
Thesenotesareanextractfrommybookofnoteswhichcanbepurchasedonebay.ie
Searchterm:leavingcertchemistrynotes
C. Hurley
Leaving Certificate Chemistry Notes 2016/2017
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2.5ShapesofMoleculesandIntermolecularForces
Simple Molecules
GENERALSHAPE
EXAMPLES
LINEAR
2BondPairs
AB2
BeH2
180o
X
B X
AB
TRIGONALPLANAR
3BondPairs
AB3
A
X
120o
B
X
X
AA
TETRAHEDRAL
4BondPairs
AB4
B
X
109.5o
A
X B
X
X
B
B
180o
H XBe
BF3
F
3-D IMAGE
X
H
X
o
B 120
X
X
FF
CH4
H
X
109.5o
C
X
H
X X
X
H
H
UsingElectronPairRepulsionTheorytoExplainShapesofMolecules
TypicalExamQuestion–Describetheshapeofammonia
1. Nhas3bondingand1non-bonding(lone)pair(EachHhas1bondpair)
2. Thebondarrangementcausestheshapeofthemoleculetobepyramidal
ElectronPairRepulsionTheory
BondAngles
1. AB3withnolonepairshasabondangleof120o
AB3with1lonepairhasabondangleof107o
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2. AB2withnolonepairshasbondangleof180o
AB2with2lonepairshasbondangleof104.5o
Theory
• Lonepairshavegreaterrepulsionofeachother–i.e.lonepairincontactwithlonepairwill
producethegreatestrepulsion,followedbylonepairincontactwithbondpairandfinallythe
weakest,bondpairincontactwithbondpair
• L.P:L.P>L.P:B.P>B.P:B.P(Repulsion)**
• Lonepairwantstogetasfarapartasgeometricallypossiblefromeachotherpushingbondscloser
together**
**Bothpointsarerequiredtogetfullmarks
ComplexMolecules
GENERALSHAPE
PYRAMIDAL
3BondPairs+1LonePair
AB3
A
X
X
B B X
B
EXAMPLES
3-D
NH3
N
o
X X 107 X
H
H
H
Ahastobeingroup5-1lonepair
V-SHAPED
2BondPairs+2LonePairs
AB2
X
H2O
A
X
B
B
Ahastobeingroup6-2lonepairs
O
104.5o
X
X
X
HH
RelationshipbetweenSymmetryandPolarityinaMolecule
B–Cl
• Electronegativitydifference=1.12
•
•
•
δ-
However,BCl3isactuallynon-polar
δ-
This is due to unequal sharing of electrons between B and Cl (i.e. Cl
polarity)cancelsduetosymmetryofmolecule
Thereforeonemayassumeitispolar
•
Centresofpositiveandnegativechargescoincide
•
BCl3hasatrigonalplanarshapewhichhassymmetry
Cl
⏐δ+
B
δ -
Cl
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IntermolecularForces
Attractive/Repulsiveattractiveforcesbetweenmolecules
TypesofIntermolecularForces:
1. VanderWaal’sforces
2. Dipole-dipole
3. HydrogenBonding
VanderWaal’sForces
Veryweakintermolecularforces
UpuntilnowH2wasrepresentedas:
H X H
givingrisetoapurecovalentintramolecularbond
But,inrealitythe2electronsinH2aremovingfromsidetosidecreatingtemporarycharges
δ
+
-
δ
H
X
H
creatingtemporarypolarity,knownasatemporarydipolewithinthe molecule
+
-
+
δ
δ
δ
δ
H
H--------------H
H
X
X
Thegreaternumberofelectronsinamolecule,thegreaternumberofpossibletemporarydipoles,and
thereforethegreaterintermolecularattraction
ThismeansthatVanderWaal’sforcesincreasewithanincreasingsizeofmolecule–i.e.biggermolecule
hasmoreelectrons
Theseweakintermolecularforcesincreasetheboilingpointwiththemoretemporarydipoles
E.g.Oxygen(16electrons)hasamuchhigherboilingpointthanHydrogen(1electron)–syllabus
Dipole-dipole
•
Intermolecularforcesbetweenpolarmolecules
•
DifferfromVanderWaal’sforcesbypermanentdipolesduetothepolarityofthemolecule
δ
+
H
•
X
-
δ
+
δ
-
δ
Cl--------HCl
Duetopermanentdipoletheboilingpointofmoleculeswithdipole-dipoleinteractionsaremuch
higherthanmoleculeswithVanderWaal
•
Syllabus: Ethene C2H4 (Mr=28) should have similar boiling point to Methanal HCHO (Mr=30),
howeverMethanalhasamuchhigherboilingpointduetostrongerintermolecularbonding
EthenecontainsVanderWaal’sforcesonly:
H
H
H
H
C=C-------------------C=C
H
H
H
H
Methanalcontainsdipole-dipoleforcesonly:
H
H
+ + δ δ δ δ C=O------------------C=O
H
H
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HydrogenBonding
Intermolecular attraction involving a slightly positive hydrogen atom bonded to a small highly
electronegativeelementsuchasF,OorN
• Hydrogenbondingisthestrongestformofintermolecularbonding
• Thisisbecausethemoleculesarehighlypolar
• E.g.inwatermolecules,O–Hishighlypolar(largeelectronegativityvalue)
• H2Sshouldhaveahigherboilingpointtowaterduetogreaterrelativemolecularmass.Butsince
theH–SbondislesspolarthantheO–Hbondinwaterithasamuchlowerboilingpointthan
water–syllabusexample
δ
-
δ+
H
H +
δ δ S--------------S δ
+
-
δ
+
δ
HO--------------H
δ
-
O
H
H H
H
VanderWaal’sandweak
HydrogenBonding
dipole–dipoleinteractions
H2Shasanelectronegativitydifferenceof0.38whichmeansitisbetweenpolarandnon-polar
ApplicationofKnowledge:DissolvingProperties
AmmoniaandWater:
δ–
N
δ– X
O
X X
+
X
X
δ H
H
δ+
H
H
HH
Process
Ø TheslightlynegativeOinwaterbondswiththeHinammonia
Ø TheslightlynegativeNinammoniabondswithHinwater
Ø Breakingofhydrogenbondsinwater
Ø Formingofhydrogenbondsbetweenammoniaandwater
Note:Eventhoughbothcompoundscontainhydrogenbonding,waterhasamuchhigherboilingpoint
becauseoflargerelectronegativitydifferenceintheOHbondthantheNHbondofammonia
2012:statehowbondinginPH3differsfromNH3,H2O,HCl
•
PH3=non-polar
•
NH3,H2O,HCl=polar
Reasonforthisdifferenceinbonding?
•
TinyelectronegativedifferentinPH3
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•
Largeelectronegativedifferenceintheothers
•
Asthebondingtypegetsstronger:
o Increaseinboilingpoint
o Increaseinmeltingpoint
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