ADVANCED CHEMISTRY 1. Philip Matthews B&& CAMBRIDGE UNIVERSITY PRESS

Transcription

1 ADVANCED CHEMISTRY 1 Philip Matthews B&& CAMBRIDGE UNIVERSITY PRESS

2 Acknowledgements How to use this book PHYSICAL CHEMISTRY 1 Elements, atoms and electrons: basic ideas 1.1 Dalton's atomic theory 1.2 Evidence for atoms 1.3 Cathode rays 1.4 Millikan's experiment 1.5 Electric Charge is quantised 2 Energy levels 2.1 Energy changes 2.2 Energy levels 2.3 Max Planck and energy levels 2.4 Light energy 3 Atoms and the nucleus 3.1 A plum pudding 3.2 How the nucleus was discovered 3.3 The discovery of protons 3.4 Moseley and atomic number 3.5 Discovery of neutrons 3.6 A comparison of electrons, protons and neutrons 3.7 Isotopes 3.8 Atomic mass units 3.9 Relative atomic and molecular masses 3.10 Einstein's equation 3.11 Binding energy 3.12 Mass defect and mass excess 4 Discovery of radioactivity 4.1 The discovery of radioactivity 4.2 New elements 4.3 Some properties of radiation 4.4 Units of radioactivity 4.5 Nuclear reactions 4.6 Artificially prepared elements 4.7 A sad ending pagex xi Radioactive decay 28 Detection of radiation 28 Half-lives 29 The radioactive decay law 31 Decay schemes 31 Nuclear energy 34 Discovery of nuclear energy 34 Fission reactions 34 Nuclear power 35 Fusion reactions 37 Nuclear weapons 38 Applications of radioactivity 41 Industrial uses of radioactivity 41 Medical uses of radioactivity 42 Radiocarbon dating 42 Chemical applications 43 Bohr's model of the atom 46 Energy levels of the hydrogen atom 46 How to calculate the ionisation energy of hydrogen 47 What are Orbitals? 48 What are stationary states? 48 Ground and excited states 49 The hydrogen atom spectrum 51 Balmer's formula for the hydrogen atom 51 Bohr's explanation 51 Other lines in the hydrogen spectrum 51 Waves and particles 54 Experimental evidence about the nature of light 54 What is wave particle duality? 56 de Broglie's equation 56 Schrödinger's theory of the atom 58 Schrödinger's theory of the hydrogen atom 58 What do the quantum numbers teil us? 59 Different types of orbital 59 Wavefunctions and what they mean 60

3 11.5 The shapes of orbitals 11.6 The spin quantum number 12 The aufbau method and electron structures 12.1 What is the aufbau method? 12.2 More about orbital energies 12.3 Filling orbitals - the importance of energy 12.4 The Pauli exclusion principle 12.5 Hund's rule 12.6 Background to Hund's rule 12.7 The aufbau method in action 13 Electron structures, ionisation energies and shielding 13.1 What is shielding? 13.2 Ionisation energies down a Group 13.3 Ionisation energies across a Period 13.4 How ionisation energies are linked to Groups in the Periodic Table 14 Bonding in molecules: valence bond theory 14.1 Valence bond theory 14.2 Dot-and-cross diagrams for diatomic molecules 14.3 Dot-and-cross diagrams for triatomic and quadratomic molecules 14.4 Dot-and-cross diagrams for hydrocarbons 14.5 Showing bonds by lines 14.6 Bonding in oxoanions 14.7 Resonance structures 15 Coordinate bonding 15.1 What is coordinate bonding? 16 Molecular orbital theory 16.1 Wavefunctions can be positive or negative 16.2 How wavefunctions can be combined 16.3 Bonding and antibonding orbitals using s orbitals 16.4 Bonding and antibonding orbitals using p orbitals 16.5 Energies of bonding and antibonding orbitals 16.6 Molecular orbitals for homopolar diatomic molecules 16.7 Molecular orbitals for heteropolar diatomic molecules 16.8 Molecular orbitals for hydrocarbons 17 Shapes of molecules 17.1 Molecular modeis 17.2 Electron repulsion theory 17.3 The isoelectronic rule 17.4 Hybridisation Ionic substances have some covalent character 101 Other evidence that a substance contains ions 102 Which elements make ionic Compounds? 103 Why do ionic Compounds exist? 103 Ionic Compounds and electron structures 104 Polar molecules and polar bonds 107 What is a polar molecule? 107 Polar bonds and electronegativities 107 Polar molecules and dipole moments 108 Polarisability 111 Intermolecular forces 113 Where are intermolecular forces found? 113 What causes intermolecular forces? 113 Dispersion forces and polarisability 114 Intermolecular forces are also produced by permanent dipoles 114 Some words of warning 114 Hydrogen bonding 117 What is hydrogen bonding? 117 Evidence for hydrogen bonding 117 Intermolecular and intramolecular hydrogen bonding 119 Hydrogen bonding in biochemistry 120 Hydrogen bonding in solids 120 Metallic bonding 122 How can you recognise a metal? 122 What is the band structure of metals? 122 Why do metals conduct electricity? 123 Semiconductors 123 Why do metals conduct heat? 126 Metal atoms exist in a sea of electrons 126 The three states of matter 128 The three states of matter 128 How do we know that gases are disorderly? 129 Differences in properties of solids, liquids and gases 129 The potential energy curve for two neighbouring molecules 130 Some remarkable substances 130 Three types of spectroscopy 136 Emission and absorption spectra 136 Electronic spectroscopy 136 Vibrational spectroscopy 136 Rotational spectroscopy 136 Translations 138 Electromagnetic waves 138 The electric field and electrons 139 The magnetic field and electrons 139 Selection rules Ionic bonding 18.1 Covalent substances have some ionic character Visible spectroscopy 142 Why does copper(n) sulphate Solution lookblue? 142 IV

4 25.2 The visible spectrum of copper(n) sulphate Solution 25.3 How does a visible light spectrometer work? 25.4 What happens to the photons absorbed by copper(n) sulphate Solution? 25.5 Why vibrations are important in visible spectra 26 Ultraviolet spectroscopy 26.1 The ultra violet spectrum of alkenes 26.2 The ultraviolet spectrum of arenes 26.3 The ultraviolet spectrum of aldehydes and ketones 27 Vibrational spectroscopy 27.1 Why is vibrational spectroscopy useful? 27.2 What are group frequencies? 27.3 Making sense of vibrational spectra 27.4 Vibrational spectra can teil us about the strengths of bonds Unit cells 179 The seven crystal Systems 179 The fourteen Bravais lattices 179 What are unit cells? 179 Radius ratio rules 184 The number of atoms or ions in a unit cell 185 Sizes of atoms, ions and molecules 188 How can we estimate the size of an atom? 188 Metallic and covalent radii 188 Van der Waals radii 189 Ionic radii 190 Bondlengths 191 Real and ideal gases 193 The gas laws 193 Real gases and the van der Waals equation 195 How good is the van der Waals equation? Nuclear magnetic resonance 28.1 The importance of nuclear spin 28.2 The patterns in an n.m.r. spectrum 28.3 Why do protons appear in different places in the spectrum? 28.4 N.m.r. spectra can teil us how many protons are present 28.5 Not only hydrogen atoms can show up in n.m.r. 29 Mass spectrometry 29.1 What are mass spectrometers? 29.2 The design of a mass spectrometer 29.3 The whole number rule and Standards of mass 29.4 Mass spectra and isotopes 29.5 Calculating relative atomic masses from mass spectra 29.6 What are fragmentation patterns? 29.7 The effect of isotopes in a molecule's mass spectrum Kinetic theory of gases 200 What is the kinetic theory of gases? 200 The pressure of an ideal gas 200 The connection between energy and temperature 201 The spread of energies in a gas 202 Kinetic theory and Avogadro's theory 203 Chemistry and gases 205 Gay-Lussac's law of combining volumes 205 Avogadro's theory 205 Dalton's law of partial pressures 206 Graham's law of diffusion 206 The mole 209 What is the mole? 209 How to work with moles of Compounds 210 Moles and equations 210 Moles and balancing equations 211 The empirical formula and molecular formula of a Compound 212 Percentage compositions X-ray diffraction 30.1 What causes X-ray diffraction? 30.2 More about diffraction 30.3 Bragg's equation 30.4 Different types of X-ray diffraction experiment 30.5 Explanation of powder photographs 30.6 The arrangement of planes in crystals 30.7 The arrangements of individual atoms 31 Crystallography 31.1 What is crystallography? 31.2 The dosest packing of atoms 31.3 Structures that are not close-packed 31.4 C oordination numbers 31.5 Metal crystals Molar masses of gases and liquids 216 Measuring the molar mass of a gas 216 Measuring the molar mass of a soluble gas 217 Measuring the molar mass of a volatile liquid 218 Moles and titrations 221 Standard Solutions 221 The concentration of a Solution 223 Concentration and molarity 224 How to do calculations involving concentrations 224 Four types of titration 227 Acid-base titrations 227 v

5 40.2 Redox titrations 40.3 Titrations involving iodine 40.4 Silver nitrate titrations 41 Oxidation numbers and oxidation states 41.1 What are oxidation and reduction reactions? 41.2 What are oxidation numbers? 41.3 Oxidation numbers of elements in covalent Compounds 41.4 Oxidation numbers of elements in ions 41.5 Rules for assigning oxidation numbers 41.6 Oxidation states 41.7 Using oxidation numbers with equations 41.8 Half-equations 42 Energy changes 42.1 Energy changes and chemical bonds 42.2 Energy changes and energy diagrams 42.3 Exothermic and endothermic reactions The Boltzmann distribution More about energy levels Entropy changes and mixing of gases Entropy and disorder Reversible and irreversible changes Some changes are spontaneous, some are not Entropy and reversible changes Entropy and non-reversible changes ( Standard entropies Calculating entropy changes Free energy 291 What is free energy? 291 Standard free energies 293 Free energy values do not teil us how fast a reaction will occur 294 Free energy changes under non-standard conditions 294 Ellingham diagrams and the extraction of metals Enthalpy 43.1 What is enthalpy? 43.2 Enthalpy and Standard states 43.3 Enthalpy and State functions 43.4 Hess's law 44 Standard enthalpies 44.1 Standard enthalpy of an dement 44.2 Standard heats of formation 44.3 Standard heats of combustion 44.4 Enthalpy changes when substances break apart 44.5 Bond energies and average bond energies 44.6 Heats of hydrogenation 45 Calculations using Hess's law 45.1 Using heats of formation 45.2 Impossible reactions 46 Lattice energies 46.1 What is meant by lattice energy? 46.2 The Born-Haber cycle 46.3 What do lattice energies teil us? Enthalpy changes in Solutions Heats of neutralisation Hydration energies Heats of Solution Enthalpies of formation of ions in Solution Equilibrium and free energy 299 What is the effect of concentration and pressure on free energy? 299 What is the connection between free energy and equilibrium? 300 Equilibrium and equilibrium constants 301 Chemical equilibrium 304 Equilibrium constants 304 Equilibrium constants and their units 305 Are equilibrium constants really constant? 306 How does temperature affect an equilibrium reaction? 306 How can the connection between equilibrium constants and temperature be made more exact? 307 Pressure can change the proportions of reactants and products at equilibrium 308 Some equilibrium reactions 314 What this unit is about 314 The bismuth trichloride water reaction 314 The chromate(vi)-dichromate(vi) reaction 314 The iodine iodine trichloride reaction 314 The iodine triiodide reaction 315 The nitrogen dioxide-dinitrogen tetraoxide reaction 315 The decomposition of ammonium salts 315 Reactions involving complex ions Internal energy What is internal energy? Taking account of work Measuring internal energy with a bomb calorimeter Measuring equilibrium constants 318 How can equilibrium constants be measured? 318 The ester equilibrium 318 The hydrogen iodide equilibrium Entropy 49.1 A first look at entropy Equilibria between phases 323 What is a phase? 323 vi

6 55.2 How to interpret a phase diagram 55.3 The phase diagram of sulphur 55.4 The phase diagram of helium 56 Chromatography 56.1 What is chromatography? 56.2 Paper chromatography 56.3 Thin layer chromatography (TLC) 56.4 Column chromatography 56.5 Ion exchange chromatography 56.6 Gas-liquid chromatography (GLC) 56.7 High pressure liquid chromatography (HPLC) 57 Polymorphism and allotropy 57.1 What is polymorphism? 57.2 What is allotropy? 58 Equilibrium between a solid and liquid 58.1 What happens when a liquid freezes? 58.2 Cooling curves 58.3 Cooling curves for mixtures 59 Solubility of salts in water 59.1 The solubility of a solid in water 59.2 Fractional crystallisation 59.3 Crystals that contain water of crystallisation 59.4 Saturated and supersaturated Solutions 60 Explaining solubilities 60.1 Why is water a good solvent for ionic crystals? 60.2 Entropy changes are important when a crystal dissolves 60.3 The sizes of the ions in a crystal are important in explaining solubilities 60.4 Why is water a good solvent for many covalent substances? 60.5 Covalent liquids often dissolve covalent solids 60.6 Volume changes when solids dissolve 61 Mixtures of liquids 61.1 What is the difference between miscible and immiscible liquids? 61.2 Raoult's law and ideal Solutions 61.3 Solutions that do not obey Raoult's law 61.4 Why are there deviations from Raoult's law? 61.5 Why do some liquids mix and others not? 62 Competition between solvents 62.1 Solvent extraction 62.2 Solvent extraction is an equilibrium process 62.3 Partition coefficients 62.4 Why do some results not fit the partition law? Distillation 365 The boiling points of mixtures 365 How distillation works 366 Industrial distillation 368 Does distillation always work? 369 Steam distillation 370 Solubility product 373 What is a solubility product? 373 Using solubility products to calculate solubilities 373 The common ion effect 375 Solubility products teil us when a precipitate will be made 375 Using solubility products in chemical analysis 376 Colligative properties 379 What are colligative properties? 379 Why does a solute influence the vapour pressure of water? 379 Elevation of boiling point 379 How to make use of the boiling point constant 380 Depression of freezing point 381 Osmotic pressure 382 Methods of measuring osmotic pressure 382 How might we explain osmosis? 383 How to calculate molar masses from osmotic pressure experiments 383 Some examples of osmosis 384 Abnormal molar masses 384 Calculating the degree of dissociation from abnormal molar masses 385 The thermodynamic explanation of colligative properties 386 Raoult's law and solids in Solution 387 Electrochemical cells 389 How an equilibrium is set up between a metal and Solution 389 The Standard hydrogen electrode 390 Standard electrode potentials 390 Combining half-cells 391 How to work out cell reactions 392 A quick way of writing cells 393 The anode and cathode in a cell 393 More about salt bridges 393 The electrochemical series 394 Some useful cells 395 Cells and concentration changes 400 How cell e.m.f.s change with concentration 400 How to work out equilibrium constants from cell e.m.f.s 401 Concentration cells 403 ph and the glass electrode Corrosion An example of corrosion 408 vn

7 68.2 The rusting of iron 68.3 How does a layer of zinc prevent iron rusting? 68.4 Why does tin protect iron from corrosion? 69 Cells and thermodynamics 69.1 The link between free energy and cell e.m.f.s 69.2 Calculating Standard e.m.f.s from free energy values 69.3 Calculating free energy values from Standard e.m.f.s How to work out the ph of a weak acid Buffer Solutions Neutralisation and titrations 455 Salt hydrolysis 455 Salts of a strong acid and a strong base 455 Salts of a strong acid and a weak base 455 Salts of a weak acid and a strong base 455 Salts of a weak acid and a weak base 456 Endpoints in titrations depend on the strength of the acid and base 456 Indicators Redox potentials 70.1 Standard redox potentials 70.2 Predicting redox reactions 70.3 Predicting reactions in the laboratory from redox potentials 70.4 Redox titrations 71 Redox Charts 71.1 What is a redox chart? 71.2 How to use redox charts 71.3 What is disproportionation? Rates of reactions 459 Why do we study the rates of reactions? 459 What makes reactions take place? 459 What can prevent reactions taking place? 460 How can we make reactions go faster? 461 Two theories of reaction rates 465 Collision theory 465 More about the activation energy 466 Catalysts and activation energy 467 Transition State theory Electrolysis 72.1 What is an electric current? 72.2 What happens during electrolysis? 72.3 Examples of electrolysis 72.4 How to calculate the mass of a substance liberated in electrolysis 72.5 Why is electrolysis used in industry? 73 Conductivity of Solutions 73.1 How do we measure conductivity? 73.2 Molar conductivities 73.3 Molar conductivities and the degree of dissociation 73.4 How individual ions contribute to conductivities 73.5 How can we make use of conductivity measurements? 74 Acids and bases 74.1 Early ideas about acids 74.2 Acids give hydrogen ions in Solution 74.3 The Brensted theory of acids and bases 74.4 The Lewis theory of acids and bases Measuring the rates of reactions 471 An example of measuring a rate 471 Six ways of measuring rates 472 Measuring the rates of very fast reactions 476 Rate laws 480 What is a rate law? 480 How can we discover the rate law? 481 Quick ways of finding the rate law 482 The contribution of individual Orders to the overall rate law 484 Reaction mechanisms 487 What is a reaction mechanism? 487 Bonds can break in two ways 487 The slowest Step in a reaction governs the rate 488 Free radical reactions 489 Mechanisms of the hydrolysis of halogenoalkanes 490 The influence of catalysts 491 The kinetics of enzyme reactions Strong and weak acids 75.1 What is the difference between strong and weak acids? 75.2 Conjugate acids and bases 75.3 The ionic produet of water 75.4 Acid dissociation equilibrium constants 75.5 What makes an acid strong? 75.6 What is the connection between ph and PKa? 75.7 Base dissociation constants and p/c b 75.8 How to work out the degree of dissociation of a weak acid INDUSTRIAL CHEMISTRY 82 The chemical industry Why is the chemical industry important? The stages in producing a new produet The economics of produetion Cash flow in the produetion cycle Running a chemical plant Designing a chemical plant Energy and mass balances Continuous and batch processing 503 vm

8 Chemical processes Examples of modern chemical manufacture Manufacture of sulphuric acid The Haber process for the manufacture of ammonia The manufacture of nitric acid The chlor-alkali industry What is the chlor-alkali industry? The production of chlorine and sodium hydroxide The ammonia-soda (Solvay) process The extraction of metals The methods of extraction Extracting the noble metals Reducing sulphide ores Reducing an oxide ore 85.5 The extraction of reactive metals 86 The oil industry 86.1 Why is the oil industry important? 86.2 Catalytic re-forming 86.3 Catalytic cracking 86.4 Thermal cracking Appendix A The laws of thermodynamics Appendix B Table of ionisation energies Appendix C Table of atomic masses Appendix D Values of some universal constants Bibliography Examination questions Answers to examination questions Subject index Index of names