University:
York University
Course:
CHEM 1001 | Chemical Dynamics
Academic year:

2022
Views:

314

Pages:

2
Author:

Niklas

Chapter 15 Activation energy, kinetic energy, and rate Orientation of collisions of rate Not all collisions occur in the correct orientation for the reaction Arrhenius equation: k = (7P)e^(-Ea/RT) = Ae^(-Ea/RT) Linear form of the Arrhenius equation: ln k = -Ea/R(1/T) + ln A A: Arrhenius factor Ea: activation energy (kJ/mol) R: gas constant (J) T: absolute temperature (K) Catalysis Some reactions with ΔG° are very slow Typically catalyzed Catalyst: a substance that speeds up a reaction without undergoing a permanent change Changes mechanism Lowers activation energy Homogeneous catalyst: catalyst is in the same phase as the reactants Heterogeneous catalyst: catalyst is in a different phase from the reactants (reaction on surface of catalyst) The rate-determining step always has the highest transition state energy, not the highest activation energy Chapter 15 Catalysis creates a new reaction pathway Thermodynamic state functions and ΔG are unaffected by a catalyst Ea is lowered the same amount for both forward and reverse reactions Heterogeneous catalysis Reaction happens on surface of catalyst Negligible rate without a catalyst Often requires breaking strong bonds Catalytic converter Uses oxidizing agents to react with reducing agents to make non-toxic chemicals Lowering Ea affects reaction rates Best catalyst binds to transition states Enzymatic catalysis Biological catalysts Used to accelerate or control reactions Enzyme active sites are ideally suited for transition state binding Each factor enhances reaction rate by greater than 10 Control of enzymes Tuned by enzyme-substrate binding affinity (Km) Competitive inhibition: binds a molecule to its active site, blocking catalytic activity Denatured enzyme: changing shape of enzyme so that it cannot react