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Created by Saravanan Sonia
almost 11 years ago
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Chemical Kinetics
Qualitative
QualitativeEnergy 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 reactantput net E into reactionendothermic 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 reactantsThus. 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 faster2) 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 E3) 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 occur4) 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
**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!!!
QuantitativeAverage 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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