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17 Cards in this Set
- Front
- Back
Rate determining step |
slowest step in any proposed mechanism |
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Collision Theory of Chemical Kinetics |
the rate of a reaction is proportional to the number of collisions per second between the reacting molecules |
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Effective Collision |
-occurs when molecules collide in the correct orientation and enough energy to break existing bonds and form new ones |
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Activation Energy |
-E(a), or energy barrier - minimum energy of collision necessary for a reaction to take place |
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Rate of reaction eqn |
rate = Z * f Z= total # of collisions per sec f = fractions of effective collisions |
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Arrhenius eqn |
For collision theory k= Ae^(-E/RT^2) k= rate constant of a rxn A = freq factor E(a) = Activation Energy R = ideal gas constant T = Temp (K) |
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Freq Factor |
-"attempt freq" - measure of how often molecules in a certain reaction collide (s^-1) |
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Transition state theory |
- "activated complex" -where old bonds break and new bonds begin to form - has higher energy than reactants and products - will dissociate into products |
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Free energy of a reaction |
- difference btwn free energy of the products and free energy o the reactants - (-) = exergonic --> energy given off - (+) = endergonic --> energy absorbed |
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Factors affecting rxn rate |
- Reaction concentrations: more reactants, more collisions per unit time - Temperature: rate increases with increasing temp (increasing KE) -Medium: generally polar solvents are preferred due to their molecular dipoles polarizing the bonds of the reactants making them longer and weaker to speed up the rxn -Catalysts: increase rxn rate without being consumed within the rxn but lowering E(a) |
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Determination of rate law |
- for all forward, irreversible rxns, rate is proportional to concentration of reactants - measured in molarity/sec - rate = k[A]^x[B]^y - k = rate constant - x & y = orders of the rxn |
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Zero- order rxns
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- rate law = k[A]^0[B]^0 = k (M/s) - only way to change rxn is by temp or catalyst - rxn vs. time = linear graph (slope = -k) |
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First order rxn |
- rate = k[A]^1 or =k[B]^1 - plotting [A] vs. t = nonlinear - plotting ln[A] vs. t = linear (slope = -k) |
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Second Order Rxn |
- rate is proportional to either the concentrations of two reactants or to the square of the concentration of a single reactant. - rate = k[A]^1[B]^1 or =k[A]^2 or = k[B]^2 - plotting [A] vs. t = nonlinear - plotting 1/[A] vs. t = linear (slope = k) |
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Electrical Potential Energy
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- like charges = + - opposite charges = - - U = kQq/r |
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Electrical Potential
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- V = U/q (J/C) OR -V = kQ/r - scalar quantity - sign determined by Q - positive charges will move to decrease electrical potential (Voltage) - negative charges will move to increaser their electrical potential (Voltage) |
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Potential Difference
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-"Voltage"= Vb-Va = W(ab)/q - W(ab) = work needed to move test charge q thru electric field from a to b. |