Catalysis

Question 1

A catalyst is a…

Answer 1

substance that increases the
rate of a reaction, without itself being
consumed by the reaction

Question 2

Types of Catalysis:

Answer 2

There are two types of catalysis:
homogeneous, and heterogeneous

Question 3

Homogeneous catalysis (1) / Heterogeneous catalysis (2) :

Answer 3

1. the catalyst and
   reactants are present in the same phase
2. the catalyst and reactants are in different phases.

Question 5

Homogeneous Catalysis:

Answer 5

• Generally, catalysts operate by lowering the
  activation energy for a reaction.
• They do this by changing the path of the reaction, i.e., by changing the mechanism of the reaction.
• Catalysts can also operate by increasing the
  number of effective collisions.
• That is, from the Arrhenius equation: catalysts
  increase k by increasing A or decreasing Ea.
• A catalyst may add intermediates to the reaction.
• Example: In the presence of Br-
  , Br2
  (aq) is
  generated as an intermediate in the decomposition of H2O2
  .

Question 6

Heterogeneous Catalysis:

Answer 6

• The catalyst is in a different phase than the
  reactants and products.
• Typical example: solid catalyst, gaseous reactants and products (catalytic converters in cars).
• Most industrial catalysts are heterogeneous.