Chemical Kinetics :D

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Chemical Kinetics

Qualitative

Qualitative

Energy Diagrams:

Activation energy (Ea): min. amt. of E required for the reactants to be converted into products

The higher the Ea, the lower the speed of reaction.

Delta H: difference in enthalphy between the products and reactants where enthalphy refers to the measure of the total energy of a thermodynamic system

If delta H (+)ve,

E of product > E of reactant

put net E into reaction

endothermic reaction

If delta H (-)ve,

E of product

remove net E out of reaction

exothermic reaction

Reversible Reactions (LOW Ea)

=> equilibria

=> constant amount of N2, H and NH3

Conc. of products = Conc. of reactants

Thus. the reaction is at equilibrium

NOTE: ALL reactions are reversible! In many cases, backward reactions is so much slower that is effectively irreversible! :D

Factors to affect reaction rates:

1) Temperature

-> the higher the temp, the faster the reaction

*increase in temp increases the E available to reactants

*speed of molecules increases

*thus, Ea is reached faster

2) Conc. of reactants

-> the higher the conc. of reactants, the higher the speed of reaction

*higher conc. -> more reactant molecules

* increases likelihood of energetic molecules bumping into each other

* NOT every collision results in a reaction due to insufficient E

3) SA of reactant molecules

-> The higher the surface area of the reactant molecules, the faster the reactions

due to having more spaces on which reactions can occur

4) Catalysts

-> work by causing the reaction to work via a new pathway with lower Ea

CHEMICAL REACTIONS RATES INCREASE BY FACTOR OF 2 FOR EVERY 10 DEGREE CELSIUS INCREASE IN TEMPERATURE!!! :D

http://www.youtube.com/watch?v=7qOFtL3VEBc (Embed)

**NOTE THAT THE DELTA E DOES NOT HAVE ANY CHANGE

Catalysts are materials that increase the rates of chemical reactions w/o being consumed

Inhibitors slow or stop reactions.... :)

PLEASE NOTE THAT INHIBITORS DO NOT INTRODUCE A NEW REACTION PATHWAY WITH HIGHER ACTIVATION ENERGY!!! INSTEAD, INHIBITORS MAY MODIFY SELECTIVITY IN ADDITION TO RATE!!!

Quantitative

Average Reaction Rate:

; where the brackets refer to the concentration in mol/dm^3

VERY SURE THAT YOU KNOW HOW TO FIND INSTANTATANEOUS

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