Here is a comprehensive summary of Units 15-25 of OCR A Level Chemistry, covering advanced topics essential for exam success:
15. Unit 15 - Chemical Equilibria: Focuses on dynamic equilibrium in chemical reactions, Le Chatelier's Principle, and equilibrium constants (Kc and Kp). The unit explains how changes in temperature, pressure, and concentration affect equilibrium positions and how these concepts are applied in industry.
16. Unit 16 - Transition Elements: Explores the chemistry of transition metals, their variable oxidation states, complex ion formation, and their role as catalysts. The unit also covers colored compounds and the unique electron configurations that give rise to their distinctive properties.
17. Unit 17 - Electrode Potentials and Fuel Cells: Examines redox reactions and the concept of electrode potentials (E°). It covers electrochemical cells, standard electrode potentials, and their use in predicting redox reactions. This unit also introduces fuel cells, their function, and their importance in sustainable energy.
18. Unit 18 - Thermodynamics: Delves into the principles of thermodynamics, including enthalpy (ΔH), entropy (ΔS), and Gibbs free energy (ΔG). This unit explains how these factors determine the spontaneity and feasibility of chemical reactions.
19. Unit 19 - Ionic Equilibria: Focuses on the behavior of acids, bases, and salts in aqueous solutions. It covers concepts such as pH, buffer solutions, and the calculation of ionization constants (Ka, Kb), as well as the importance of ionic equilibria in biological and environmental systems.
20. Unit 20 - Aromatic Chemistry: Covers the structure and properties of benzene and other aromatic compounds. Key reactions include electrophilic substitution (nitration, halogenation) and the stability of the aromatic ring. This unit emphasizes the industrial applications of aromatic chemistry.
21. Unit 21 - Carbonyl Compounds: Focuses on the chemistry of aldehydes and ketones, including nucleophilic addition reactions, oxidation, and reduction. The unit highlights the importance of carbonyl compounds in organic synthesis and industry.
22. Unit 22 - Carboxylic Acids and Esters: Explores the structure, properties, and reactions of carboxylic acids and esters. This unit covers esterification, hydrolysis, and the significance of these compounds in biological systems and industrial processes.
23. Unit 23 - Nitrogen Compounds: Focuses on the chemistry of amines, amides, and amino acids. The unit covers their properties, synthesis, and reactivity, and emphasizes their importance in pharmaceuticals, proteins, and industrial chemistry.
24. Unit 24 - Polymers: Examines both addition and condensation polymers, their methods of production, and their properties. The unit also discusses environmental issues related to polymers, including recycling and biodegradability.
25. Unit 25 - Analytical Techniques: Provides an overview of modern analytical techniques used to identify and quantify chemical substances, including infrared (IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, and chromatography. These techniques are essential for structure determination and quality control in chemistry.
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Definitions
reversible reaction constant concentrations 1 Temperature
Dynamicequilibrium temperature favoursendothermic
system is closed direction
rate offorward rate
ofbackward
constant concentrations
all othermeasurable variables are unchanging
Equilibrium Law 2 Concentration
a Atb B E e C t d D at co
4 A shifttoright to opposechange
temperature
A a x B EET moiam
an the
aspect
nceneration
constant
3 Pressure
guilibrium
Kc 0 equalconcentrations t pressure shift towardsto sidewith
fewermoles ofgas
But T pressure T rate in both
Chemical
directions but 4 rate
offorward
reaction more
EquilibriumConstantKp
a Atb B E e C t d D
Equilibria 4 Catalyst
d
P c xp D speedsuprate of forward and backward
Kp p a a xp B reaction equally no effect on the
position of equilibria
450 C
Catalystoffinely dividediron
mama
200 atm
Compromise between cost and yield
N2 342 2 NH
nm
I mixknownquantitiesofproducts and
reactants
2 Setup manyexperimentswithdifferent
amounts
3 Allow equilibrium is established
4 Keep temperature constant
5 Colorimeter measure withoutdisturbing
Calculate Kc or Kp
, Definitions Reactions
Transition elements d block elements with an oxidationstate 1 Precipitation
with partially filled d subshell
a at 204 a Hao OH 242
Remember the 4s
fills before the 3d and is emptied
beforethe 3d Coat 204 fo Hao OH 242
Properties
Feat 204 Fe Hao OH 242
I variable oxidation States Mn't 204 MnHao OH 242
eg Fest Fest Cut Cut
2 Coloured ions
Electrons can jump from a lower energy d orbital to an
unoccupied higher energy d orbital art 304 Er Hao OH 342
3 Catalytic behaviour
2 Ligand substitutions
Heterogeneous catalyst
molecules adsorb onto surface of catalyst Cachao t 204 a one Hao 242
Fixes orientation increases moleculesperunit weakens Nhs H2O NhaOH
the bonds as it withdraws e density a Hao t INI a NH 4201774h
Molecules react Cachao t HCL I Cuda 6420
ransition
Products desorb from Observedcolour
the catalyst's surface co no 4cL Coca 6h20
observedcolour
Nat342 É 2nA y y new g er Mao
Er om 401 307
38ft er om 401 34
2502 02 5 250 Creon 3h20
Homogeneous catalyst er om Hao GNH CrNhs 3420 30
catalyst in same phase as reactants
2Fe't H2O 2 Fe t 24 02 Co on 42014 GNH CoNhs t 204 442
2Fe t 2Mt H2O 2Fe t 2420
4 Complexes
central positiveion surrounded
complexion
byligands coordinately bonded to it
Co ordination number numberofligands co ordinately
bonded d
Chelating ligand can co ordinate from morethan I
atom at once
Bidentate ligand can co ordinate from two positions
H NY
I DNN H NO
d NH
cis trans
Naming 1 Tetrahedral
on
or onion
cyano gangs
snaissen
ligandsthen 8951
opticalisomerism
OH Ch
hydroxo Da a
cis trans
02 oxo 2 Square planar
H2O aqua an
ngfifinna pignus
pigun
1800
NH3 ammine Cl a N
Pt mannn Naa man na na
mycis Hst a opticalisomerism
trans