Catalyst

Question 1

Catalysts

Answer 1

A material that enhances the rate of a chemical reaction and in the process is cyclically regenerated.

Question 2

Catalysts do not..

Answer 2

affect the equilibrium constant

Question 3

Catalysts provide alternative pathways for reactions to proceed by…

Answer 3

• stabilising transition state from the uncatalysed reaction
• allowing formation of a new transition state that is more stable than the uncatalysed one

Question 4

Eact

Answer 4

the difference in internal energy between the transition state and the reactants

Question 5

How does a catalyst work?

Answer 5

Reduce Eact

Question 6

Conversion

Answer 6

= the mole % of reactant that has reacted

=100([A]initial-[A]final)/[A]initial

Question 7

Acitivity

Answer 7

initial rate of reaction

The rate of reaction where the linear relationship between rate and concentration is maintained.

Question 8

Activity (equation)

Answer 8

Activity = -d[A]/dt =d[B]/dt = d[C]/dt

Question 9

Selectivity

Answer 9

=100(yield ofspecific product) / total yield  
#or
yield/conversion x 100

Question 10

TON

Answer 10

turnover number

Question 11

turnover number

Answer 11

number of reactions a single site can achieve before failure

Question 12

TOF

Answer 12

turnover frequency

Question 13

Turnover frequency

Answer 13

The number of reactions that occur per site per unit time

TOF=reaction rate / number of active sites

Question 14

Biocatalyst

Answer 14

Any biological species that satisfies the conditions to be described as a catalyst.

Question 15

Examples of biocatalyst

Answer 15

bacteria
fungi
enzymes

Question 16

Phase Transfer Catalysis

Answer 16

Transfer reagents from a phase they are soluble in, into a phase that they are not very soluble in order to allow them to react

Question 17

Homogeneous Catalysis

Answer 17

All catalytic processes where the catalyst is soluble in whatever “medium” the reaction is taking place in.
Reagent & catalyst are same phase

Question 18

Homogenous advantages

Answer 18

• very selective
• mild conditions
• well defined species –> easier mechanism–> easier to improve

Question 19

Homogenous Disadvantage

Answer 19

• same phase so can be difficult to separate
• -> therefore hard to recycle
• batch manner –> not continuous –> inefficient

Question 20

Heterogeneous Catalysis

Answer 20

Catalyst is in different phase to reactants
Reaction occurs at the interface between two phases –> on surface of the catalyst
usually gas/liquid reacting on solid surface

Question 21

Heterogeneous Advantage

Answer 21

• efficient continuous

- easy to separate

Question 22

Heterogeneous Disadvantage

Answer 22

• relatively slow
• difficult conditions to operate
• hard to achieve selectivity
• less well defined –> harder to understand and improve