Catalysis
Catalysis Mechanisms
Learning Objectives:
- Understand the fundamental concept of catalysis and its role in enhancing the rate of chemical reactions.
- Differentiate between homogeneous, heterogeneous, and enzymatic catalysts, recognizing their distinctive characteristics and applications.
Catalysis is the process of increasing the rate of a chemical reaction by the addition of a substance known as a catalyst. Catalysts remain unchanged at the end of the reaction.
Catalysts can be classified into homogeneous (dissolved in the same phase as reactants), heterogeneous (in a different phase), and enzymatic (biological catalysts) based on their nature.
Catalysis is widely used in the chemical industry for processes like refining petroleum, producing chemicals, and environmental applications (e.g., catalytic converters).
Solved Example: 9189-01
The substance that increases the speed of a chemical reaction is called?
A. Inhibitor
B. Promoter
C. Catalyst
D. Moderator
Correct Answer: C
Solved Example: 9189-02
Substances that decrease the activity of a catalyst are known as:
A. Controllers
B. Promoters
C. Poisons
D. Initiators
Correct Answer: C
Solved Example: 9189-03
At the end of the chemical reaction the catalyst remains:
A. Unchanged in quantity but changed in composition
B. Unchanged in quantity and composition
C. Unchanged in composition but changed in quantity
D. Changed in quantity and composition
Correct Answer: B
Solved Example: 9189-04
Which of the following is not an example of heterogeneous catalytic reaction?
A. Haber's process
B. Combustion of coal
C. Hydrogenation of vegetable oils
D. Ostwald's process
Correct Answer: B
Solved Example: 9189-05
Which of the following Catalyst is used during the Hydrogenation of Oils?
A. Pb
B. Ni
C. Pt
D. Cu
Correct Answer: B
Solved Example: 9467-01
What is the purpose of a promoter in catalysis?
A. Inhibiting the reaction
B. Enhancing the selectivity of the catalyst
C. Increasing the activity of the catalyst
D. Maintaining equilibrium in the reaction
Correct Answer: C
Solved Example: 9467-02
In enzymatic catalysis, the active site of an enzyme:
A. Remains unchanged after the reaction
B. Binds permanently with the substrate
C. Undergoes structural changes during the reaction
D. Inhibits the reaction rate
Correct Answer: C
Biocatalysis
Learning Objectives:
- Define biocatalysis and explain its significance.
- Understand the distinction between biocatalysis and traditional chemical catalysis.
A Catalyst is a substance which alters the rate of chemical reaction.
A Biocatalyst is a substance, especially enzymes or microbes, that initiates or modifies the rate of chemical reaction in a living body.
Advantages of Biocatalysts:
- Biocatalysts, like catalysts, increase the speed of chemical reactions but do not affect the thermodynamics of the reactions.
- Biocatalysts have high selectivity.
- High catalytic efficiency and mild operational conditions.
- Biocatalytic characteristics can be tailored with protein engineering and metabolic engineering methods to meet the desired process conditions.
Disadvantages of Biocatalysts:
- Limited operating regions, substrate or product inhibition, and reactions in only aqueous solutions.
Solved Example: 9191-01
Enzymes are biocatalysts and they catalyse biochemical reactions. Which of the following reactions is NOT catalysed by an enzyme?
A. Unwinding of two strands of DNA
B. Dissolution of CO$_2$ in water
C. Formation of peptide bond
D. Hydrolysis of sucrose
Correct Answer: B
Solved Example: 9469-01
What is the primary advantage of using enzymes in biocatalysis?
A. They are highly resistant to high temperatures
B. They are specific and efficient catalysts
C. They are only effective in acidic conditions
D. They are easily recyclable
Correct Answer: B
Solved Example: 9469-02
In biocatalysis, what role do enzymes play in chemical reactions?
A. Initiators of reactions
B. Inhibitors of reactions
C. Catalysts that accelerate reactions
D. Solvents that dissolve reactants
Correct Answer: C
Solved Example: 9469-03
Which of the following is a common application of biocatalysis in the production of chemicals?
A. Steam reforming
B. Polymerization
C. Fermentation
D. Distillation
Correct Answer: C
Physical Properties of Catalysis
Types of Catalysts:
- Homogeneous Catalysis: Catalysts exist in the same phase as the reactants.
- Heterogeneous Catalysis: Catalysts exist in a different phase (often solid) from the reactants.
- Activity: The ability of a catalyst to increase reaction rates.
- Selectivity: The ability to favor specific reaction pathways or products.
- Stability: Catalysts should maintain their structure and activity over time.
Solved Example: 9283-01
Which of the following is not an example of heterogeneous catalytic reaction?
A. Haber's process
B. Combustion of coal
C. Hydrogenation of vegetable oils
D. Ostwald's process
Correct Answer: B
Solved Example: 9283-02
At the end of the chemical reaction the catalyst remains:
A. Unchanged in quantity but changed in composition
B. Unchanged in quantity and composition
C. Unchanged in composition but changed in quantity
D. Changed in quantity and composition
Correct Answer: B