Q1. What is catalysis?
a) The process of converting solids into liquids
b) The process of speeding up chemical reactions
c) The process of converting gases into solids
d) The process of slowing down chemical reactions
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Correct Answer: b) The process of speeding up chemical reactions
Explanation: Catalysis is the process of speeding up chemical reactions by lowering the activation energy required for the reaction to occur. A substance known as a catalyst facilitates the reaction without being consumed in the process. Catalysts work by providing an alternative reaction pathway with lower energy barriers, allowing reactant molecules to undergo transformations more readily. This results in increased reaction rates and efficiency. Catalysis plays a crucial role in various industrial processes, including petroleum refining, pharmaceutical synthesis, and environmental remediation, by enabling faster and more selective reactions.
Q2. Which of the following is not a type of catalysis?
a) Homogeneous catalysis
b) Heterogeneous catalysis
c) Photochemical catalysis
d) Thermal catalysis
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Correct Answer: d) Thermal catalysis
Explanation: Thermal catalysis is not a distinct type of catalysis. Instead, it refers to catalytic reactions that occur at elevated temperatures, often involving the activation of catalysts through thermal energy. Homogeneous catalysis involves catalysts in the same phase as the reactants, while heterogeneous catalysis involves catalysts in a different phase. Photochemical catalysis utilizes light energy to drive chemical reactions. However, thermal catalysis simply describes the use of heat to facilitate catalytic reactions, which can occur in both homogeneous and heterogeneous systems.
Q3. Which type of catalysis involves catalysts in different phases from the reactants?
a) Homogeneous catalysis
b) Heterogeneous catalysis
c) Photochemical catalysis
d) Thermal catalysis
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Correct Answer: b) Heterogeneous catalysis
Explanation: Heterogeneous catalysis involves catalysts that are in a different phase from the reactants. For example, a solid catalyst may catalyze a reaction in a gaseous or liquid phase. This type of catalysis is common in industrial processes due to its ease of separation and recycling of catalysts. Homogeneous catalysis, on the other hand, involves catalysts that are in the same phase as the reactants, such as dissolved in a liquid phase. Heterogeneous catalysis plays a significant role in numerous chemical processes, including ammonia synthesis and petroleum refining.
Q4. Which of the following is an example of enzymatic catalysis?
a) Hydrolysis of sucrose by acid
b) Decomposition of hydrogen peroxide by manganese dioxide
c) Conversion of glucose to ethanol by yeast
d) Oxidation of methane to carbon dioxide and water
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Correct Answer: c) Conversion of glucose to ethanol by yeast
Explanation: Enzymatic catalysis involves the use of biological catalysts called enzymes to facilitate chemical reactions within living organisms. An example of enzymatic catalysis is the conversion of glucose to ethanol by yeast during fermentation. Yeast enzymes catalyze this reaction, breaking down glucose into ethanol and carbon dioxide. Enzymatic catalysis is highly specific and efficient, playing essential roles in metabolism, digestion, and various biochemical processes in organisms.
Q5. What is a promoter in catalysis?
a) A substance that inhibits catalytic activity
b) A substance that enhances catalytic activity
c) A substance that remains unchanged during catalysis
d) A substance that acts as a solvent for reactants
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Correct Answer: b) A substance that enhances catalytic activity
Explanation: In catalysis, a promoter is a substance that enhances the catalytic activity of a catalyst. Promoters work in conjunction with catalysts to improve reaction rates, selectivity, or stability. They may alter the surface properties of the catalyst or provide additional active sites for reaction intermediates to adsorb and react. Promoters play a vital role in optimizing catalytic processes for industrial applications, where fine-tuning the performance of catalysts can lead to improved efficiency and product quality.
Q6. Which type of catalysis involves the use of light energy to drive chemical reactions?
a) Homogeneous catalysis
b) Heterogeneous catalysis
c) Photochemical catalysis
d) Thermal catalysis
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Correct Answer: c) Photochemical catalysis
Explanation: Photochemical catalysis involves the use of light energy to drive chemical reactions. Catalysts, known as photocatalysts, absorb photons from light sources, promoting electron transfer processes that initiate or accelerate reactions. Photochemical catalysis is particularly useful for reactions that require high-energy intermediates or involve radical species. It finds applications in organic synthesis, environmental remediation, and energy conversion processes, where it offers advantages such as mild reaction conditions and selectivity.
Q7. Which of the following is an example of industrial heterogeneous catalysis?
a) Haber-Bosch process for ammonia synthesis
b) Enzymatic hydrolysis of starch to glucose
c) Fischer-Tropsch synthesis for hydrocarbon production
d) Hydrogenation of vegetable oils for margarine production
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Correct Answer: a) Haber-Bosch process for ammonia synthesis
Explanation: The Haber-Bosch process for ammonia synthesis is a classic example of industrial heterogeneous catalysis. In this process, nitrogen and hydrogen gases react over a solid iron catalyst at high temperatures and pressures to produce ammonia. The iron catalyst facilitates the formation of ammonia from nitrogen and hydrogen molecules by providing suitable reaction pathways and active sites for adsorption and reaction. The Haber-Bosch process is crucial for the production of ammonia-based fertilizers, contributing significantly to global food production.
Q8. Which type of catalysis occurs when a catalyst is present in the same phase as the reactants?
a) Homogeneous catalysis
b) Heterogeneous catalysis
c) Photochemical catalysis
d) Thermal catalysis
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Correct Answer: a) Homogeneous catalysis
Explanation: Homogeneous catalysis occurs when a catalyst is present in the same phase as the reactants. For example, catalysts dissolved in a liquid phase can catalyze reactions involving other dissolved reactants. Homogeneous catalysis often involves coordination complexes or organometallic compounds as catalysts. It offers advantages such as uniform reaction conditions and high catalytic activity. Homogeneous catalysis is widely used in organic synthesis, polymerization, and fine chemical production.
Q9. Which of the following is not a role of catalysts in catalysis?
a) Increasing reaction rates
b) Lowering activation energy
c) Altering equilibrium constants
d) Consuming reactants
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Correct Answer: d) Consuming reactants
Explanation: Catalysts in catalysis do not consume reactants; instead, they facilitate reactions without being consumed themselves. Catalysts increase reaction rates by providing alternative reaction pathways with lower activation energies, allowing reactants to transform into products more readily. They do not alter equilibrium constants but may affect the rate at which equilibrium is reached. Catalysts play essential roles in improving reaction efficiency, selectivity, and yield in various chemical processes.
Q10. Which of the following is a characteristic feature of catalysts in catalysis?
a) They remain unchanged in chemical composition
b) They act as solvents for reactants
c) They inhibit reaction rates
d) They have higher activation energies than reactants
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Correct Answer: a) They remain unchanged in chemical composition
Explanation: A characteristic feature of catalysts in catalysis is that they remain unchanged in chemical composition throughout the catalytic process. Catalysts facilitate chemical reactions by providing an alternative reaction pathway, lowering the activation energy required for the reaction to occur. While catalysts participate in the reaction mechanism, they are not consumed in the process and can be recovered unchanged at the end of the reaction. This ability to undergo multiple reaction cycles without being consumed makes catalysts highly efficient and economical for industrial applications. Additionally, catalysts do not act as solvents for reactants but rather provide active sites for reactant molecules to adsorb and undergo transformation. Moreover, catalysts typically have lower activation energies than reactants, enabling them to accelerate reactions effectively.