Transcript CH101 General Chemistry - 유룡

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
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http://rryoo.kaist.ac.kr
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CH101 General Chemistry I
Spring Semester 2010
Textbook:
“University Chemistry”
by Peter Siska
(Benjamin Cummings, 2006)
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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).
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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”.
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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)

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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
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Course Schedule
Week
Content
Note*
1st
Introduction / Chap. 2. The Quantum Revolution
2nd
Chap. 2. The Quantum Revolution
Reading
Assignment:
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
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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
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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
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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.
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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
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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
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Nano Chemistry: New Opportunity
Molecules
10-10 m
Cluster :
Nanopartilces:
(2~100 molecules) hundred~million
10-9~10-8 m
Quantum Dots of CdSe
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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
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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
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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
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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
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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)
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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
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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
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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)
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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
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The Charge on the Electron
Millikan’s oil drop experiment
The Charge on the Electron
Millikan’s raw expt data
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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
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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)
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Unified mass scale
relative atomic mass is assigned using C12 isotope as
the reference.
12
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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
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Department of Chemistry, KAIST
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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 )(6.02211023 amu g 1 )(1atom Al / 26.98 amu)
= 6.02211023 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
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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
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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
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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