generalchem_ls_01.pdf

7/26/2019 GeneralChem_LS_01.pdf

1/35

8/5/2012BITSPilani, Pilani Campus

CHEM F111 General Chemistry

BITSPilaniPilani Campus


2/35


General Chemistry CHEM F111):An Introduction

Text Books:

T1: P.W. Atkins and Julio de Paula, Elements of Physical

Chemistry: 5th

Edition, Oxford University Press, Oxford2009

T2: T. W. Graham Solomons and Craig B. Fryhle, Organic

Chemistry, 8thEdition, John Wiley & Sons, Inc. New York,

2004.


3/35


Reference Books:

R1: J. D. Lee, Concise Inorganic Chemistry, 5thEdition,

Blackwell Science, Oxford, 1999.

R2: R. T. Morrison and R. Boyd, Organic Chemistry, 6th

Edition, PHI, New Delhi, 1992.



4/35


Quantum theory

Atomic structure and spectra

Chemical bonding

Spectroscopy of various types



5/35


Chemical reaction thermodynamics

Chemical Kinetics

Electrochemistry



6/35


Conformations

Stereochemistry

Different types of reactions



7/35


Aromatic compounds

Coordination compounds

Structure and stability

Chelates and Isomerism



8/35


Component Duration Wt % Date/Time Remarks

Mid Semester

Test

90

min

30% 7.10.2012

4.00 - 5.30

pm

Closed

book

Tutorial 25% Continuous*

ComprehensiveExamination

180min

45%

16%Quiz

5.12.2012Forenoon

Closedbook

29% Do Open

book



9/35


*Tutorial Hour

A review of the highlights of the materials covered

in the lecturesFurther discussion and interactions

Clarification of doubts

Problem solving

Periodical and continuous evaluation



10/35


Tutorial Hour Tests: Two typesA set of objective type questions (different types),

which the student will have to answer and submit

during the tutorial class.A set of problems will be assigned periodically, of

which one to be solved in the tutorial hour of the

following week.Students must attend the tutorial section in which

they are registered.



11/35


Quantum Theory



12/35


Why Quantum Theory??

Description of motion of physical objects (ClassicalMechanics/ Newtonian mechanics) used till early

20thcentury is suitable for macroscopic objects

Any kind of motion can be excited to any arbitrary

value of the energy

A particle travels in a trajectory, a path with a

precisely defined position and momentum at eachinstant

Waves and particles are distinct concepts


13/35


The idea of duality

is rooted in a debate

over the nature of

light and matterdating back to the

1600s.

Christiaan Huygens

1629 -1695

light consists of

waves

Sir Isaac Newton

1643 -1727

light consists of

particles

Why Quantum Theory??


14/35


Quantum Theory

These are excellent approximations at the macroscopiclevel, but break down when one considers the behavior of

microscopic entities such as electrons, atoms, molecules

etc.

Black body radiation

Photoelectric effect


15/35


Quantum Theory

Line spectra of atoms

Heat capacity of solids


16/35


Quantum Theory

People RARELY get quantum mechanics of their

first exposure.

Many aspects of quantum mechanics are counter

intuitive and thus, visual learnerswill likely have

more trouble than those that tend to think in the

abstract.

We will introduce it now in hopes it will be easier

the more you are exposed to it.


17/35


Blackbody

Any object radiates energy. The amount of energy

emitted, and its frequency distribution depends on

the temperature and on the material.

Black body: It is truly a theoretical object that

absorbs all radiation (100%!) that falls on it.

Some materials, eg., graphite approximate such

behavior or a pinhole in a container


18/35


Blackbody Radiation

Blackbody radiation:

The radiation emitted

from the hole is called

blackbody radiation.

Problem: To account for

the spectral distribution

of the power emitted by

a black body.


19/35


Quantum Theory

Wiensdisplacement law:

Can be used in

measuring the

temperature on the

surface of the sun.

maxT = 2.9 mm K(Constant)

The peak of the curve shifts towards longer

wavelength as the temperature falls and it satisfie

max


20/35


Quantum Theory

The radiation energy is

proportional to the 4thpower of

the associated temperature.Emittance M = aT4

(Power emitted per unit Surface

Area and proportional toEnergy density)

a=5.67 x 10-10Wm-2K-4

Stefan and Boltzmanns law:


21/35


Quantum Theory

The above laws describes the blackbody radiation

very well.

The problem exists in the relation between the

radiation power M(T) and the wavelength .

Two typical theoretical formulas for blackbody

radiation was proposed: One is given by Rayleighand Jeansand the other by Wein.


22/35


Quantum Theory

In 1890, Rayleigh and Jeans obtained a formula

using the classical electromagnetic (Maxwell)

theory and the classical equipartition theorem ofenergy in thermotics.

It states that the density of energy in a region of

the eletromagnetic field due to radiation ofwavelength is proportion to 1/4

Rayleigh-Jeans Law

TCKTDensityEnergy T4

1

4

, 8)(


23/35


Quantum Theory

Rayleigh-Jeans formulawas correct for very long

wavelength in the far

infrared but hopelessly

wrong in the visible light

and ultraviolet region.

Energy density rises without bound as decreases

It was regarded as ultraviolet Catastrophe.


24/35


Quantum Theory

Weinsformula:

Later on in 1896, Wein derived another important

formula using thermodynamics.

T

C

eCTM 3

5

2)(

Unfortunately, this formula is only valid in the short

wavelengths region.


25/35


Quantum Theory

Plancks Magic formulaCrucial assumption that

Planck make that an

oscillator of frequency

cannot be excited to any

arbitrary energy, but only

to integral multiples of a

fundamental unit orquantum of energy hi.e.,

E = nh, n = 0,1,2,.h = 6.626 x 10-34J s,

the Planck constant,


26/35


Quantum Theory

Plancksdistribution dE = dWhere Energy density () = (8hc/5)(ehc/kT- 1)-1

cis the speed of light, kis Boltzmannsconstant and

his Plancksconstant.

Planck proposed

empirical formula describe

the curve of blackbodyradiation exactly for all

wavelengths.


27/35


Quantum Theory

Success of Plancks formula:

= 8hc / {5(ehc/kT- 1)}

aT4 ; Stefan Boltzman

Law is obtained

Integrate overdto get total

power radiated

Take derivative of

w-r-t to get peak

maxT ; Wiens

displacement Law is

obtained


28/35


Quantum Theory


= 8hc / {5(ehc/kT- 1)}

At small , ehc/kTfaster than 5

(Exponential is large)

0 as 0

Energy density0 as 0UV Catastrophe avoided


29/35


Quantum Theory

For very large wavelength, when 1Tk

hc

2

2

11

Tk

hc

Tk

hce Tk

hc

Drop the second order and higher order terms, and

Rayleigh-Jeansformula could be obtained.



30/35


Quantum Theory


For smaller wavelength of blackbody radiation,

Tkhc

Tk

hc e

e

1

1

Weinsformula can be obtained.


31/35


Quantum Theory

Plancks empirical formula matched all thedifferent classical physics results obtained by the

Maxwell electromagnetic theory, thermodynamics

and statistics! However, no one knew why at thattime. This phenomenon seemed unbelievable,

incredible and even impossible, but is true!

Planck himself did not believe his such a wonderfulhypothesis and he spent about ten years to solve

the same problem using classical physics.


32/35


Quantum Theory

Photoelectric Effect


33/35


Quantum Theory

Observations

No emission of electrons if the frequency of

radiation is below a threshold value characteristic

of the metal.

Kinetic energy of emitted electrons varies

linearly with the frequency, and is independent of

light intensity.

For frequencies above the threshold value,

emission of electrons is instantaneous, no matter

how low the intensity of the light.


34/35


Quantum Theory

Explanation (EINSTEIN 1905)Light of frequency may be considered as a

collection of particles, called photons, each of

energy h.If the minimum energy required to remove an

electron from the metal surface is (work

function), then if h< , no emission of electronsoccurs

Threshold frequency 0given by = h0


35/35

8/5/2012

Quantum Theory

Explanation (EINSTEIN 1905)

For > 0, thekinetic energy of

the emitted

electron Ek

= h

= h(0).

generalchem_ls_01.pdf

Documents