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Introduction to CH101H: General Chemistry I Dear Class of 2011: Congratulations & Welcome to KAIST! Prof. Ryong Ryoo (유룡 교수) Email: [email protected] Tel: 042-869-2830 Office: Natural Science Building Rm 1106 (자연과학동 1106호) http://rryoo.kaist.ac.kr 2 CH101 General Chemistry I Spring Semester 2010 Textbook: “University Chemistry” by Peter Siska (Benjamin Cummings, 2006) 3 General Guidelines: 1) You need to read the textbook before you come to the class, because it may be very difficult to understand lectures given in English during your first semester at KAIST. All basic lecture notes can be downloaded from the General Chemistry Website, http://www.gencheminkaist.pe.kr, or a link be found at http://chem.kaist.ac.kr. 2) There are mandatory Quiz Sessions led by Teaching Assistants (TAs) from 7 to 7:30 pm on Mondays, after the full coverage of each chapter in the class. Quiz covers the chapter lectured in the previous week(s). 4 3) There are Practice Sessions led by TAs from 7:45 to 8:45 pm every Mondays. The Practice Sessions are not mandatory, and only those students who need extra discussions and problem-solving need to participate. 4) You should read a chapter before the chapter is started in the class, and submit your “Study Summary” of the chapter in the Quiz Session (see the lecture schedule). You have to write your Study Summary “by hand” and “in English”. 5 Grade Policy 95-100pts: A+, 90-95pts: A0, 85-90pts: A 80-85pts: B+, 75-80pts: B0, 70-75pts: B 65-70pts: C+, 60-65pts: C0, 55-60pts: C 50-55pts: D+, 45-50pts: D0, 40-45pts: D 0-40pts: F 1) Mid-Term Exam: 30pts 2) Final Exam: 30pts 3) Study Summary: 10pts 4) Quiz: 10pts 5) Attendance & Attitude: 20pts (1-pt deduction for each missing class and unacceptable attitude; can be negative) 6 Chap1-Physical Principles Underlying Chemistry Chap2-Quantum Revolution H H=E Chap3-Wave Mechanics, Hydrogen atom O H sp3 hybrid Chap4-Many-Electron Chap5-Valence Electron, Chap6-Valence Bond Atoms, Periodic Table Chemical Behavior Model DE=q+w Chap7-Molecular Orbital Chap8-Molecular Motion Model and Spectroscopy 7 Course Schedule Week Content Note* 1st Introduction / Chap. 2. The Quantum Revolution 2nd Chap. 2. The Quantum Revolution Reading Assign ment: Chap. 1 SS: Chap. 2 3rd Chap. 3. Wave Mechanics and the Hydrogen Atom SS: Chap. 3 4th Chap. 3. Wave Mechanics and the Hydrogen Atom Q: Chap. 2 5th Chap. 4. Atoms with Many Electrons and the Periodic Table SS: Chap. 4 6th Chap. 4 / Chap. 5 7th Chap. 5. Valence Electron Configurations, Periodicity, and Chemical Behavior Mid-term Exam (Chap. 2 – Chap. 5) 8th Q: Chap. 3 SS: Chap. 5 Q: Chap. 4 *Q: the coverage of Quiz. SS:The coverage of Study Summary 8 9th Chap. 6. Orbitals and Chemical Bonding I 10th Chap. 6. Orbitals and Chemical Bonding I 11th Chap. 7.Orbitals and Chemical Bonding II Q: Chap. 6 SS: Chap. 7 12th Chap. 7.Orbitals and Chemical Bonding II KCS (04.28-29) 13th Chap. 8. Molecular Motion and Spectroscopy SS: Chap. 8 14th Chap. 8. Molecular Motion and Spectroscopy Q: Chap. 7 15th (Chap. 8) / Review 16th Final Exam (Chap. 6 – Chap. 8) SS: Chap. 6 9 What is Chemistry? Objectives of Modern Chemistry Units of Measure e Force, Work, Energy Electrical Nature of Matter Coulomb Force, Potential Energy A Z X Nucleus, Isotopes 10 Chap 1. Physical Principles Underlying Chemistry 1.1 The Province of Chemistry Chemistry A branch of the natural science which deals with the material world in terms of the atomic theory of matter. A science that deals with the composition, structure, and properties of substances and with the transformations that they undergo. 11 is the study of matter, its structure, properties, the changes that matter undergoes, and the energy associated with these changes. Role of Chemistry in Scientific Disciplines 13 Modern Chemistry Two distinct roots: ① Theoretical side – Early Greek philosophy ② Experimental side – Alchemy in the ancient Middle East Can be classified into Analytical, inorganic, organic, physical chemistry “Interdisciplinary” like materials chemistry Nano, Environmental, etc… Can also classified as ① Synthesis and structure of matter ② Kinetics and dynamics involved in its transformation Materials: Central Role in our Modern Life Ziegler Natta 1965, Nobel Prize in Chemistry 15 Nano Chemistry: New Opportunity Molecules 10-10 m Cluster : Nanopartilces: (2~100 molecules) hundred~million 10-9~10-8 m Quantum Dots of CdSe 16 Carbon Allotropy: beyond our Imagination Graphite Fullerene: C60 1996 Nobel Prize in Chemistry (Curl, Kroto, Smalley) Diamond Carbon Nanotubes 1991 Sumio Iijima (NEC) 1.2 Objectives of Modern Chemistry Modern chemistry – launched by R. Boyle (17c) (defining ‘element’) Elements vs. Compound or Mixture H.Cavendish (1766): hydrogen + air → water (water is not an element, but a compound) J. Priestley and A. Lavoisier established the air → a mixture of gases hydrogen + oxygen → water Lavoisier’s finding has led the law of conservation of mass 18 Law of Conservation of Mass In any physical or chemical change, mass is neither created nor destroyed. Lavoisier’s vessel (a)Hg + Air → HgO +Air The total mass has been increased (b) 2Fe + pure O2 → 2FeO establishing conservation of mass 19 20 Law of Definite Proportion For a given compound, the ratio of masses between composition elements is invariable. (ex. mO/mH in water = 8:1) Law of Multiple Proportions For more than one compounds of a given pair of elements, the mass ratio of an element in both compounds is always a small whole number. (ex. the ratio between carbon dioxide and carbon monoxide = 2) Atomic Theory - J. Dalton The matter is composed of tiny indestructible atoms. Each element consists of tiny atoms. H + O → HO Law of Combining Volumes - Gay-Lussac The volumes of reacting gases are in the ratio of small whole number. Two volumes of hydrogen combined with one of oxygen to make two of steam. 2H2 + O2 → 2H2O 21 The Periodic Law The law (D.Mendeleyev, 1872) → organized all known elements into a table arranged by increasing mass whose columns defined chemical families The Periodic Law Later, instead of atomic mass, chemists simply numbered the elements from 1 to 92: atomic number Z H. Moseley: atomic number Z (not atomic mass) is the natural ordering parameter for elements Atomic number Z: number of positive charges in nucleus 23 Modern Questions Identity and Composition, Structure and Reactivity 2H2 + O2 → 2H2O (1.1) 1. Why? H2, O2: gases, H2O: liquid 2. Reaction – needs a spark to initiate - proceeds explosively with heat evolution Why the spark? 3. Nature of the bonding force of H2O 4. Geometry of H2O and geometric parameters, 5. Details of the reshuffling of atoms for the reaction We need Models Observations new Models 1.3 Units of Measure length, mass, time, electric charges: Fundamental physical quantities in chemistry ① cgs-esu , ② SI (Système International) 26 Errors in Measurement Precision and accuracy – presented by the significant figures of the data (ex. 3.2637±0.0001(A) vs. 3.26±0.01(B)) A: higher precisions, larger number of significant figures Precision – inherent capability of a measuring device Accuracy – closeness of the measurement to the “true” values 27 Precision and accuracy in the laboratory. precise and accurate precise but not accurate Precision and accuracy in the laboratory. random error systematic error 1.4 Force, Work, and Energy Energy is the capacity to do work. Potential Energy Kinetic Energy energy due to the position of the object or energy from a chemical reaction due to a chemical state energy due to the motion of the object Potential and kinetic energy can be interconverted. Temperature and Heat Energy Heat energy Mechanical energy possessed by the constituent molecules of an object. Kelvin (K) or Absolute temperature T(K) = t(0C) + 273.15 Average energy of a molecule k BT Boltzmann’s constant 31 1.5 The Electrical Nature of Matter Electrical discharge tube [cation: positive ion, anion: negative..] - Cathode rays → negatively charged particle streams of electricity (electrons) emanating from the cathode (J. Thomson, 1890) 32 1.5 The Electrical Nature of Matter The charge-to-mass ratio q/m = -5.2728 x 1017esu g-1 = -1.7588 x 1011C kg-1 Charge-to-mass ratio of positive ions The gas in the tube is Ionized into Electron and Positive Ions Positive ions (Anode Rays !) - achieved by reversing the cathode-anode - ratio of q/m → highly dependent on the gas fill, highest value for the lightest element (H), 1836 times smaller than for the electron - For electrical neutrality, H ion carries an equal but opposite charge to that of electron with 1836 times heavier - Model for the atom (proposed by Thomson): a number of electrons and same numbers of protons 34 35 The Charge on the Electron Millikan’s oil drop experiment The Charge on the Electron Millikan’s raw expt data 36 e = 4.803204 x 10-10esu = 1.602176 x 10-19C Mass of an electron me = 9.10938 x 10-28 g Mass of the positive ion mp = 1.672622 x 10-24 g Department of Chemistry, KAIST Millikan Library at Caltech 37 38 1.6 The Nuclear Atom Rutherford’s α-particle scattering apparatus - Experiment carried out in vacuum - Viewing microscope sealed into a rotatable hollow cylinder surrounding the stationary source and foil target - Angle-dependence of the scattering - Backward scattering - Nucleus → composed of Z protons, and ca. same numbers of neutrons in 10-13cm in dia. (J.Chadwick) out of 10-8cm of the atomic diameter. mn = 1.674927 x 10-24g - The same numbers, Z, of electrons → in atomic orbit. Imagine shooting a rifle at a mound of loose snow. “You fired a 15-inch shell at a piece of tissue paper and it came back to you !!!” Isotopes (Ch 16) A Z X A- Mass No. (protons + neutrons) Z- Atomic No. (protons) X-Chemical symbol Isotopes - same atomic number and different mass numbers (ex. 1020 Ne, 1021Ne, and 1022 Ne ) Mass defect – Heavier atoms weigh < protons + electrons + neutrons → The mass converts into the binding energy (E = mc2) 41 Unified mass scale relative atomic mass is assigned using C12 isotope as the reference. 12 6 mass( C ) = 12.0 amu AM (atomic mass)- Weighted average of natural abundances of isotopes ex. AM of carbon atom: AM(C) = (0.9890)(12.00) + (0.0110)(13.00) = 12.01 42 Department of Chemistry, KAIST 43 44 Avogadro’s Number and the Mole The mass of the proton 1.007276 amu = 1.67262 x 10-24 g (1 proton + 1 electron) 1 amu = 1.66054 x 10-24 g The number of amu in a gram = 6.0221 x 1023 amu g-1 => This is Avogadro’s number NA * Exactly 26.98 g of aluminum metal (26.98 g Al )(6.02211023 amu g 1 )(1atom Al / 26.98 amu) = 6.02211023 atoms Al 26.98 g Al is special since it cancel out 26.98 amu. This special 26.98 g contains 6.0221 x 1023 atoms = 1 mol Atomic Mass of Al = 26.98 amu/atom = 26.98 g/mol 45 Avogadro’s Number and the Mole Avogadro’s number NA no. of atoms in an atomic mass: 6.0221 x 1023 atoms = 1 mole Stoichiometry relations between moles in a chemical equation ex. 2H2 + O2 → 2 H2O 2 mol 1 mol 2 mol Department of Chemistry, KAIST 46 3 Usual Ways to Calculate the number of moles 1) Pure solid or liquid: grams divided by grams/mole Al, 2.698 g 2.698/26.98 = 0.1000 mol 2) Gas: apply the Ideal gas law (PV = nRT) 1 mole of gas: 22.4 L (1L = 1000 cm3 = 10-3 m3) air bag, 2NaN3(s) 2Na(s) + 3N2(g) 13.002 g(65.01 g/mol) 3) 6.72 L Solution: moles/liter = M Cola drink, sugar 27.25 g/250 mL = 109.0 g/L = 0.6050 mole Department of Chemistry, KAIST 47 1.7 Coulomb Force and Potential Energy Coulomb’s law q1, q2 – charges on two bodies r – distance between them Coulomb force (or electromagnetic force) attractive q1, q2 – opposite sign repulsive q1, q2 – same sign Mutual potential energy V = r2 r1 r2 dr 1 1 kq1q2 dr = kq1q2 2 = kq1q2 2 r1 r r r2 r1 1 electron/1 proton system, with r1 → ∞ ← negative of work required to pull the electron completely away from the nucleus