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16 Cards in this Set
- Front
- Back
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Rate constant
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Proportionality constant (k) in rate law
E.g. for a 1st order reaction: rate = k[concn] |
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First order reactions
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Rate directly proportional to concentration of reactant.
Rate = [A] |
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Half life
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Time for concentration of reactant to fall to half itsinitial value
E.g. for a 1st order reaction t½ =ln2/k |
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Rate law
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Relationship between rate and concentration
E. g. rate = [A] |
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Second order reaction |
Rate proportional to square of concentration Rate = [A]2 |
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Zero-order reaction |
Ratedoes not depend on concentration |
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Activation energy |
The energy required by reactants to reach transition state. |
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Catalyst |
Substance affecting rate of reaction, but is unchanged at the end e.g. Pt in hydrogenation of alkenes. |
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Reaction rate |
Change in concentration per unit time |
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Oscillating reaction |
Reaction in which intermediates appear and disappear periodically, and final products appear in bursts rather than continuously. |
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Heterogeneous catalyst |
Substance not in same phase as reactants affecting reaction rate but unchanged at the end of the reaction E.g. Pt in hydrogenation of alkenes |
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Elementary rxn |
An individual step in a complex reaction, or A reaction with only one step |
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Units of first order rxn |
Unitss-1 |
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Units of second order rxn? |
L mol-1 s-1 |
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Calculating rate constant? |
K = rate/([A]x[B]) E.g. if both first order [A]x[B] E.g. if one first and one second [A]x[B]2 |
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Activation energy if k1-2 and t1-2 known |
1. ln (k2/k1) x R 2. (1/T2 – 1/T1) 3. (1) / (2) In J mol or kJ mol as appropriate |
