5.7 Catalysis

• Catalysts affect the reaction rate by lowering the activation energy.
• Match the type of catalyst with its interaction with reactants:

  Homogeneous ↔️ Reacts directly in solution

  Heterogeneous ↔️ Reacts on the surface
• The first step in the mechanism of catalyst action is adsorption
• Match the effect of a catalyst with its absence:

  Lowers activation energy ↔️ Higher activation energy

  Increases reaction rate ↔️ Slower reaction rate

  Catalyst is not consumed ↔️ Catalyst is not present
• An example of a heterogeneous catalyst is solid metal catalysts in hydrogenation reactions.
• The activation energy is the minimum energy required for the reactants to reach the transition state.


  True
• Match the industrial or biological example with the correct catalyst:

  Petroleum cracking ↔️ Zeolites

  Metabolic processes ↔️ Enzymes
• One method of catalyst regeneration is solvent washing.
• Reactive poisoning involves the chemical reaction of the poison with the catalyst, altering its structure
• What is the mechanism of adsorptive poisoning?

  Physical blockage of active sites
• Heating a sulfur-poisoned platinum catalyst in oxygen converts sulfur compounds to sulfur dioxide.


  True
• Platinum group metal catalysts in catalytic converters convert harmful pollutants into less toxic substances.


  True
• What happens to the activation energy of a reaction when a catalyst is used?

  It decreases
• What is the minimum energy required for reactants to reach the transition state and form products?

  Activation energy
• What is activation energy?

  Minimum energy for reaction
• Catalysts are consumed during a reaction.

  False
• What is catalyst poisoning?

  Substance blocks active sites
• Match the type of poisoning with its mechanism:

  Adsorptive poisoning ↔️ Physical blockage of active sites

  Reactive poisoning ↔️ Chemical reaction with catalyst
• Zeolite catalysts in petroleum cracking break down long hydrocarbon chains
• What is a catalyst and what is its role in chemical reactions?

  Increases reaction rate without consumption
• What is the key difference between homogeneous and heterogeneous catalysts?

  Phase relative to reactants
• Arrange the steps in the mechanism of catalyst action:

  1️⃣ Adsorption

  2️⃣ Activation

  3️⃣ Reaction

  4️⃣ Desorption
• What is the role of a catalyst in a chemical reaction?

  Lower activation energy
• Homogeneous catalysts exist in the same phase as the reactants, allowing direct interactions.

  True
• Steps in the hydrogenation of alkenes using platinum as a catalyst:

  1️⃣ Platinum surface adsorbs the alkene and hydrogen

  2️⃣ Bond breaking and formation occur
• Catalysts increase the overall reaction rate by providing an alternative pathway with lower activation energy.
• Reactive poisoning occurs when a poison chemically reacts with the catalyst, altering its structure.

  True
• What type of poisoning involves the physical blockage of active sites by poison molecules?

  Adsorptive poisoning
• Sulfur compounds on platinum catalysts can be removed by heating in an oxygen-rich atmosphere
• Catalyst regeneration involves removing the poison to restore catalyst functionality
• The Haber-Bosch process uses a heterogeneous iron catalyst to produce ammonia from nitrogen and hydrogen
• A catalyst increases the rate of a chemical reaction by providing an alternative pathway with a lower activation energy
• Match the type of catalyst with its phase and example:

  Homogeneous ↔️ Same phase as reactants ||| Enzymes in biochemical reactions

  Heterogeneous ↔️ Different phase from reactants ||| Solid metal catalysts in hydrogenation reactions
• The first step in the mechanism of catalyst action is the adsorption of reactants onto the catalyst surface
• Steps in the mechanism of catalyst action

  1️⃣ Adsorption of reactants

  2️⃣ Lowering activation energy

  3️⃣ Chemical transformation on catalyst

  4️⃣ Desorption of products
• Match the catalyst with its application:

  Zeolites ↔️ Petroleum cracking

  Enzymes ↔️ Metabolic processes
• Reactive poisoning involves a chemical reaction with the catalyst.

  True
• How can sulfur compounds be removed from platinum catalysts?

  Heating in oxygen-rich atmosphere
• What type of catalysts are enzymes?

  Biological catalysts
• Catalysts increase the activation energy of a reaction.

  False