CYL110 Elements of Physical Chemistry

8/14/2019 CYL110 Elements of Physical Chemistry

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CYL110

Elements of Physical Chemistry

Chemical Thermodynamics

Chemical Dynamics

Quantum Chemistry


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CHEMICAL THERMODYNAMICS

A. Ramanan

QUANTUM CHEMISTRY

Dr. Sidhdharth Pandey

A. RAMANAN

MS729

[email protected]


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Thermodynamics is the only science about

which I am firmly convinced that, within the

framework of the applicability of its basic

principles, it will never be overthrown.

Albert Einstein


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LECTURE 1

Properties of Gases


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CaCO3(s) Ca2+(aq) + CO3

2-(aq)

CO2(aq) + H2O(l) H2CO3(aq)

H2CO3(aq) + CO32-(aq) 2HCO3

-

Ca2+(aq) + 2HCO3- CO2(aq) +

H2O(l) + CaCO3(s)

CO2


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A. Ramanan

Department of Chemistry

Power generation percent of different energy


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1 1Mexico1 7France2 0Italy2 2Korea2 5Britain4 2Canada2 8Germany0 3India2 5Japan2 7Russia0 74China5 44America

Exhaust amount ofper person (ton)Exhaustpercent(wt%)

Global carbon dioxide generation by mineral fuel

(from Scientific American 2002)Global carbon dioxide generation by mineral fuel

(from Scientific American 2002)


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Hydrogen

Antoine Laurent Lavoisier (1743-1794), French

chemist, who disproved the phlogiston theory by

determining the role of oxygen in combustion, and

organized the classification of compounds.

The name Hydrogen was given by :

Henry Cavendish. 1731-1810. British chemist and physicist

who discovered the properties of hydrogen and established

that water is a compound of hydrogen and oxygen.

Cavendish called hydrogen flammable air.


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A. Ramanan

Department of Chemistry

Volumetric and gravimetric hydrogen density

of some selected hydrides.

Three options exist for storing hydrogen: as a highly compressed gas,

a cryogenic liquid, or in a solid matrix.

James A. Ritter Materials today, September 2003, 24


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15 MPa compressed hydrogen gas cylinder

The hydrogen storage capacity is only 1.2 mass%.


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35 and 70MPa compressed

hydrogen gas cylinders

100 MPa compressed H2

cylinder is also being

developed.

The hydrogen storage is about 2.7% at 35 MPa and 5.5 mass% at 70 MPa.

Dangerous!


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Hydrogen storage in liquid state has high storagecapacity, but it resumes a lot of energy in liquefation

and low temperature keeping, therefore, the energy

utilization efficiency is low.

Hydrogen storage in liquid state


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Volume for storage of 4 kg H2 in different states

Solid material


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H2(g) + O2(g) H2O(l)

H2(g) and O2(g) mixes violently

when initiated liberating heat

~240kJ/mol

E ~ 2.3 eV


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C (solid)

graphite

diamond

C60
http://images.google.co.in/imgres?imgurl=http://nanobugle.files.wordpress.com/2009/04/fullerene.jpg&imgrefurl=http://nanobugle.wordpress.com/2009/04/24/fullerene-carbon-nanotubes-for-cancer-treatment/&usg=__yj_XMaLv_Z7V89pUmi0r8AbPGkM=&h=196&w=196&sz=10&hl=en&start=156&um=1&tbnid=X4WdYHCMi2s4AM:&tbnh=104&tbnw=104&prev=/images?q=fullerene+applications&ndsp=20&hl=en&sa=N&start=140&um=1http://www.lauraspetportraits.co.uk/website-images/graphite-pencil-pic.jpghttp://images.google.co.in/imgres?imgurl=http://www.garysuttonshow.com/wp-content/uploads/2009/03/diamond.jpg&imgrefurl=http://www.garysuttonshow.com/smart-tips-on-diamond-insurance/&usg=__PsdVSK8LHkOEAWpPYD7vadz0hlU=&h=506&w=337&sz=34&hl=en&start=45&um=1&tbnid=sAl7K6O8M7FaLM:&tbnh=131&tbnw=87&prev=/images?q=diamond&ndsp=20&hl=en&sa=N&start=40&um=1


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Thermodynamics is the branch ofscience that predicts whether a state of

some macroscopic system will remainunchanged or will spontaneously evolve toa new state.

Kineticsis the branch of science thatdeals with how long it takes for a systemto reach that new state.


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Spontaneous Processes A process that is spontaneous in one direction is not

spontaneous in the opposite direction. The direction of a spontaneous process can depend

on temperature:

Ice turning to water is spontaneous at T > 0C

Water turning to ice is spontaneous at T< 0C


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Reversible Processes

A reversible process is one that can go back and forth

between states under exactly the same conditions (the

definition ofequilibrium!).

When 1 mol of water is frozen at 1 atm at 0C to form1 mol of ice, q=Hfus of heat is removed.

To reverse the process, q=Hfus must be added tothe 1 mol of ice at 0C and 1 atm to form 1 mol ofwater at 0C.

Therefore, converting between 1 mol of ice and 1 molof water at 0C is a reversible process.

Chemical systems in equilibrium are reversible.


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Irreversible Processes

When 1 mol of ice melts spontaneously in a

warm room, it is an irreversible process;

water does not freeze in a warm room!

In any spontaneous process, the path

between reactants and products isirreversible.


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Spontaneous Processes

Thermodynamics predicts the direction of a

spontaneous process; it cannot predict the speedatwhich the process will occur.

Most spontaneous processes are exothermic; they"roll down the enthalpy hill".

But some spontaneous processes are notexothermic; WHY?


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Thermodynamics is most relevant to theunderstanding of processes on spatial scales large

enough to neglect individual atoms andtimescales long enough to neglect kinetics, sothat the predictions of thermodynamics describeto good approximation the actual state of nature,

rather than the expected state at infinite time.All kinetic processes go faster with increasingtemperature, and hence the tools ofthermodynamics are most useful

But even for kinetically limited things (likelife), thermodynamics tells which way it isfavorable for processes to run.

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CYL110 Elements of Physical Chemistry