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Physical Chemistry. Dónal Leech [email protected] Ext 3563 Room C205, Physical Chemistry. Notes for downloading (powerpoint and word) http://www.nuigalway.ie/chem/Donal/Teaching.htm. Chemistry. Physical Sciences Sub-atomic Atoms Materials Atmosphere Stellar.

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Physical chemistry
Physical Chemistry

Dónal Leech

[email protected]

Ext 3563

Room C205, Physical Chemistry

Notes for downloading (powerpoint and word)

http://www.nuigalway.ie/chem/Donal/Teaching.htm


Chemistry
Chemistry

  • Physical Sciences

  • Sub-atomic

  • Atoms

  • Materials

  • Atmosphere

  • Stellar

  • Biological Sciences

  • Organisms

  • Organs

  • Tissues

  • Cells

  • DNA

Chemistry

  • Molecules

  • Bonds

  • Forces

Molecular Sciences


Physical chemistry1
Physical Chemistry

Establishes and develops the principles that are used to explain and interpret the observations made in chemistry

Bulk  Individual  Rates

Thermodynamics   Chemical reactions

Quantum mechanics & spectroscopy

Equilibrium  Structure  Change

ENERGY


Textbook
Textbook

  • Brown, LeMay, Bursten

  • Chemistry: The Central Science, 9th Edition

    Companion Web-site

    http://www.prenhall.com/brown


Dynamic equilibrium chapter 15

Dynamic EquilibriumChapter 15

Example

liquid + heat vapour

an endothermic physical change


Le chatelier s principle
Le Chatelier’s Principle

  • When a dynamic equilibrium is upset by a disturbance, the system responds in a direction that tends to counteract the disturbance and, if possible, restore equilibrium

liquid + heat

vapour

Increase the temperature (add heat)


Le chatelier s principle1
Le Chatelier’s Principle

  • When a dynamic equilibrium is upset by a disturbance, the system responds in a direction that tends to counteract the disturbance and, if possible, restore equilibrium

vapour

liquid + heat 

Liquid evapourates to absorb the added heat and the position of the equilibrium shifts to the right


Solution of a weak acid
Solution of a Weak Acid

CH3COOH + H2O H3O++CH3COO-

For a given composition of a system, equilibrium is independent of which side you approach it from…..reactions are REVERSIBLE

N2O4(g)  2NO2(g)

Cinit 0.0350 mol 0

or 0 0.0700 mol

Cequil 0.0292 mol 0.0116 mol


Equilibrium Lawsimple relationship between molar concentrations (or pressures) of reactants and products at equilibrium

H2(g) + I2(g)  2HI(g) (at 440C)

Mass action expression:

Where Q is the reaction quotient

LAW: at equilibrium the reaction quotient is equal to the equilibrium constant, K.

In general for

dD + eE  gG + hH


Heterogeneous equilibria involving more than one phase
Heterogeneous Equilibria(involving more than one phase)


Equilibrium law for gaseous reactions
Equilibrium Law for Gaseous Reactions

For gaseous reactions use partial pressures, P, to give an equilibrium constant (Kp)


Predicting direction of equilibrium changes le chatelier redux
Predicting direction of equilibrium changes(Le Chatelier redux)

Adding or removing reactant or product

Cu(H2O) 42+(aq.) + 4Cl-(aq.) CuCl 42-(aq.) + 4H2O

Changing volume (or pressure)-gases only

as liquids and solids are incompressible

Decrease V=>increase P

System opposes this by reducing the number of molecules


Predicting direction of equilibrium changes(Le Chatelier redux)

Changing temperature (heat)

System opposes this by trying to absorb the added heat

ONLY factor that actually changes the value of K

Effect of catalyst

Speeds up approach to equilibrium, but does not

alter K or the system (kinetics)


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