Summary of Lec 6.1 - Catalysis

Summary of Scientific Concepts and Discoveries

• Catalysts:
  • Definition: A catalyst is a substance that increases the rate of a chemical reaction without undergoing any permanent change itself.
  • Types of Catalysts:
    • Homogeneous Catalysis: Catalyst and reactants are in the same phase (e.g., all in a liquid solution).
    • Heterogeneous Catalysis: Catalyst and reactants are in different phases (e.g., solid catalyst with liquid or gas reactants).
    • Homogeneous Biological Catalysts: Biological molecules (e.g., enzymes, RNA) acting as Catalysts within a medium (often aqueous).
• Activation Energy:

  Catalysts provide an alternative reaction pathway with lower Activation Energy, allowing more molecules to reach the necessary energy for the reaction to occur.

• Applications of Catalysis:
  • Catalysts are extensively used in the chemical industry, including the production of fertilizers and various products.
  • Examples include the catalytic converters in vehicles that reduce harmful emissions and the use of platinum as a catalyst in reactions involving hydrogen and oxygen.
• Kinetics and Rate Constants:

  The presence of a catalyst significantly increases the rate constant of a reaction, exemplified by a problem involving the decomposition of hydrogen peroxide where the rate constant increased by a factor of 2,100 with the addition of iodide ion.

• Catalyst Activity and Selectivity:
  • Activity: Refers to how effectively a catalyst speeds up a reaction.
  • Selectivity: Indicates the preference of a catalyst for a particular reaction over others, minimizing side reactions.
• Thermodynamics of Catalysis:

  Catalysts do not affect the extent of the reaction (how far it goes) but speed up both the forward and reverse reactions equally.

• Challenges and Research:

  Research is ongoing to find cheaper and more effective Catalysts, particularly in processes like oil refining and fuel cells.

Methodology and Problems Presented

• Example Problem:

  Calculate the increase in the rate constant when a catalyst is added, using the activation energies provided.

• Factors Affecting Reaction Rates:
  • Temperature
  • pH (concentration of hydronium ions)
  • Concentration of reactants and Catalysts

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