Arrhenius Theory and Catalysts Flashcards Preview

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Flashcards in Arrhenius Theory and Catalysts Deck (17)
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1
Q

Why does the rate of reaction depend on the activation energy?

A

o The rate of a reaction depends on the height of the barrier (the activation energy) because only a small fraction of the number of molecules at a given temperature have a sufficient energy to get over the barrier

2
Q

Describe the plot of the Arrhenius Equation

A

 If one constructs a plot of ln k vs 1/T the slope of the plot will be -Ea/R and the intercept will be ln A

3
Q

What is catalyst?

A

o A catalyst is a substance that speeds up the rate of a chemical reaction but is not consumed during the course of the reaction

4
Q

What is the transition state of interest?

A

 The transition state of interest for a given reaction is the highest energy point along the lowest energy path

5
Q

What is Catalysis?

A

o Catalysis is the lowering of the energy barrier to speed up a reaction

6
Q

What is the activation energy?

A

 The height of a barrier along the reaction pathway is the activation energy

7
Q

What is the mechanism of an enzyme?

A

Substrate + Enzyme Complex -> Product

8
Q

What are enzymes?

A

o Enzymes are biological catalysts
 They are proteins that fold into particular conformations such that they can help speed up very particular chemical reactions

9
Q

What is a reaction coordinate?

A

o A reaction coordinate is a path that links the reactant molecules and the products molecules

10
Q

What are the two types of catalysts?

A

o Catalysts in the same phase as the chemical reactants are called homogeneous catalysts, while those in different phases are called heterogeneous catalysts

11
Q

Where do intermediates lie on a reaction coordinate?

A

o Any minima that exist between the reactants and the products along the reaction coordinate are intermediates

12
Q

What is the Boltzmann distribution?

A

at a given temperature there is a distribution of kinetic energies for all the molecules in a sample

13
Q

What is the transition state?

A

 The transition state is the high energy point between two minima along the reaction coordinate

14
Q

Where does the substrate bind to the enzyme?

A

at the active site

15
Q

What is the pre-exponential factor?

A

• The pre-exponential factor is the ultimate rate of the reaction; it is the fastest the reaction could ever proceed (if barrier were zero or the temperature were infinite)

16
Q

How does a catalyst work? (3)

A

o They provide a means for the reactant molecules to break bonds and then form temporary bonds with the catalyst
o Some catalysts change during the course of the chemical reaction, but are then returned to their original state at the end of the reaction
o Catalysts can also function by “holding” molecules in particular configuration while simultaneously weakening some particular bonds
 This allows the catalyst to essentially “help” the chemistry by arranging the reactants in favorable geometries as well as by weakening bonds that need to break along the reaction coordinate

17
Q

What is Arrhenius Law?

A

o Arrhenius Law states that the rate of a reaction can be increased by increasing the temperature