Physical Chemistry. Tutor: Dr. Jia Falong

Transcription

1 Physical Chemistry Professor Jeffrey R. Reimers FAA School of Chemistry, The University of Sydney NSW 2006 Australia Room 702 Chemistry School CCNU Tutor: Dr. Jia Falong Text: Atkins 9 th Edition assumed to be read before each lecture starting from the beginning slow and deep treatment Chapter 1 this week next week Chapter 2 or Chapter 3??? must know tomorrow Assessment: to be finalized next week - 50% exam (mid semester and end semester) - 20% tutorial exercises - 30% tutorial discussion plus challenge questions Challenge Questions- small assignments set in lectures for volunteers to do talk to me or Dr. Jia after the lecture for help, make small presentation to class at next lecture. To be shared amongst those that want to do them.

2 TextBook Web resources - Living figures - Road Maps (see text page 911) - show relationships between equations - (answering any calculation question involves selecting paths from the roadmap - Web links. 3 rd party sites of interest - Ebook whole text book online needs activation code from front of your text

3 Student's solutions manual to accompany Atkins' Physical Chemistry 9/e Ninth Edition Charles Trapp, Marshall Cady, and Carmen Giunta 608 pages 246x189mm Paperback 29 July 2010 Price: 28.99

4 Lecture timetable Tuesday 2:00 to 3:40 Wednesday 2:00 to 3:40 Thursday 8:50 to 9:40 Weeks starting Tuesday 8 th Oct 15 th Oct 22 rd Oct 29 th Oct 5 th Nov 12 th Nov I am way Nov. Tutorial 26 th Nov and 27 th Nov??? I depart Thursday 28 th Nov

5 Page 1 Chapter F: Assumed Fundamentals Atomic mass M g/mol back cover M = 1,12,14 for H,C,N etc see text Molecules are made up of atoms at well defined geometries Molecular mass is the sum of its atomic masses Number of moles = actual mass / molecular mass n = m / M There are Avagadro s number of molecules per mole N A = x

6 Molecules are held together by bonds single, double, triple covalent bonds ionic bonds other types too

7 Physical Chemistry Fundamentals: Figure F.1

8 Physical Chemistry Chapter 1: Figure F.2

9 Polar bonds arise owing to mixing of covalent and ionic character dipole, quadrapole, octapole moments Eg. Water Q= 0.33 e H Q= e O H Dipole Moment Q= 0.33 e µ = atoms i= 1 = 1.8 Debye rq i i e = magnitude of the charge on the electron, x Coulombs The atomic charges provide a simple model depicting the average locations of the electrons. The dipole moment is a physical observable that is measured very accurately using microwave spectroscopy.

10 Intermolecular interactions cause molecules to condense into liquids and solids (including biological material) - Eg., electrostatic, hydrogen bonding, dispersion interactions Electrostatic interactions given by Coulomb s Law: - Unlike charges attract - condensation lowers the Coulomb potential energy V V 12 mol 1 mol 2 = i j QQ i 4πε r 0 j ij

11 Thermal motion opposes condensation: Kinetic Energy = atoms 1 mv 2 dr Atomic velocity = v i i = dt kt Classical mechanics : the average energy = per degree of freedom 2 k = Boltzmann's constant, T = temperature every atom in a moleule has 3 degrees of freedom representing motion in x, y, and z directions E k = i 2 i

12 - Classical mechanics predicts that motion stops at absolute zero T = 0 (note don t need to say 0 K, the unit is meaningless here; also room temperature is 298 K or 25 C) - Quantum mechanics indicates that motion can never stop H O r OH = Å H 1 Å (Ångstrom) = m Minimum allowed motion of each atom in each direction ± 0.1 Å!!!

13 Quantum mechanics allows only discrete energy levels for rotational, vibrational, and electronic motions Commonly used units of energy: hc E = hν = Spectroscopists: λ wavenumber = 1 / wavelength Physicists: E = QV ev energy = charge voltage Chemists: kcal/mol Text books: kj/mol 1 ev 8065 cm -1 1 kcal/mo l= kj/mol 1 ev = kcal/mol 1 kcal/mol 350 cm -1 At 298 K, RT = kj/mol = kcal/mol = ev cm -1. R = gas constant = N A k

14 Quantum mechanics demands that the relative populations of each energy level be given by the Boltzmann Equation N N i j = ( E E )/ kt e i j where i and j are the level indices, N their populations, and E their energies

15 Physical Chemistry Chapter 1: Figure F.5 Increasing temperature Relative population N N N i j = ( E E )/ kt e i j

16 Physical Chemistry Chapter 1: Figure F.6 E N E cm / N Relative populations at room temperature kt = cm -1. N i N Vibrational & Electronic: 0 = e ( E E )/ kt Rotational: i 0 N i N 0 i = (2i + 1) e ( E E )/ kt 0

17 But translational motions not quantized Quantum mechanics reduces to the classical Maxwell-Boltzmann Equation v = velocity of molecule M = molar mass of molecule f(v)= probability distribution

18 Physical Chemistry Chapter 1: Figure F.7

19 Living graph hyperlink Fig F.7 You will find it on the web site

20 Molecules interact with the electric and magnetic fields associated with electromagnetic radiation

21 Physical Chemistry Chapter 1: Figure F.8

22 Physical Chemistry Chapter 1: Figure F.9 Rotational transitions Vibrational transitions Electronic transitions

23 Physical Chemistry Chapter 1: Figure F.10

24 Why students never ask questions in lectures in China chain saw

25 Tutorial Exercises F2.5, F2.6 F3.1, F3.3 F4.1, F4.2, F4.3 F5.1 F5.2 F5.3 F5.5 F5.6 F6.1 + convert to ev, cm -1, kj/mol, kcal/mol F7.4

26 Unused figures from textbook

27 Physical Chemistry Chapter 1: Table F.1

28 Physical Chemistry Chapter 1: Table F.2

29 Physical Chemistry Chapter 1: Table F.3

30 Physical Chemistry Chapter 1: Table F.4

31 Physical Chemistry Chapter 1: Figure F.3