transition metal catalyst

• What is a catalyst?

  A catalyst is a chemical that speeds up the rate of a reaction without being used up or changed itself.
• How do catalysts speed up reactions?

  They provide an alternative pathway that has a lower activation energy.
• What catalyst is used in the Haber process to make ammonia?

  An iron catalyst is used in the Haber process.
• What catalyst is used in hydrogenation reactions?

  A nickel catalyst is used in hydrogenation reactions.
• What catalysts are commonly used in catalytic converters?

  Platinum, palladium, and rhodium are commonly used in catalytic converters.
• What is the best catalyst for the decomposition of hydrogen peroxide in experiments?

  Manganese dioxide is the best catalyst for the decomposition of hydrogen peroxide.
• What transition metal is used in the contact process?

  Vanadium is used in the contact process.
• Why do transition metals make good catalysts?

  They have multiple stable oxidation states and can readily lose and gain their s and d electrons.
• Why are metals from Group 1 or Group 2 less likely to be good catalysts?

  They only exist in a single oxidation state and have completely filled d sub-shells.
• What are the two types of catalysts based on their phase relative to the reactants?

  • Heterogeneous catalysts: Different phase from reactants (e.g., solid catalyst with gaseous reactants).
  • Homogeneous catalysts: Same phase as reactants (e.g., catalyst in solution with aqueous reactants).
• What is an active site in the context of catalysts?

  An active site is the region where reactants adhere and interact with each other on a catalyst.
• What are the three key stages in the working of a heterogeneous catalyst?

  1. Adsorption: Reactants adhere to the active site.
  2. Bond breaking and making: Bonds are broken and new bonds are formed.
  3. Desorption: Newly made products are released from the active site.
• What is the difference between adsorption and absorption?

  Adsorption means sticking to the outside, while absorption means being taken inside.
• Why is the strength of the bonds between the reactant and transition metal important for catalysis?

  If the interaction is too weak, reactants may move away before interacting; if too strong, the active site may be blocked.
• Why is silver not a very good transition metal catalyst?

  Silver tends to have interactions that are too weak for effective catalysis.
• What problem does tungsten face as a catalyst?

  Tungsten can catalyze reactions, but the products never dissolve, blocking the active site.
• How do the stages of catalysis help in reducing activation energy?

  Each stage has its own activation energy, allowing the reaction to proceed with less energy at each step.
• What is one method used to maximize the surface area of a catalyst in industry?

  Using a support medium to spread the catalyst over a larger area.
• What is the contact process used for?

  The contact process is used to produce large quantities of sulfuric acid in industry.
• What is the first reaction in the contact process involving sulfur dioxide and oxygen?

  Sulfur dioxide reacts with oxygen to make sulfur trioxide.
• What is a problem associated with using platinum as a catalyst in the contact process?


  Platinum can become poisoned by arsenic, which absorbs to its active sites.
• What is the oxidation state of vanadium in vanadium pentoxide?

  The oxidation state of vanadium in vanadium pentoxide is +5.
• What happens to vanadium during the reaction with sulfur dioxide in the contact process?

  Vanadium is reduced from an oxidation state of +5 to +4.
• Why can't a catalyst be used up in a reaction?

  A catalyst cannot be used up because it is not changed by the chemical reaction.
• What is the role of vanadium pentoxide in the contact process?

  Vanadium pentoxide acts as a heterogeneous catalyst in the contact process.
• What impurities are often found in sulfur feedstocks used for production?

  Arsenic impurities
• What catalyst is commonly used nowadays instead of sulfur feedstocks?

  Vanadium pentoxide
• What is the oxidation state of oxygen in vanadium pentoxide?

  • 2
• What is the oxidation state of vanadium in vanadium pentoxide?

  +5
• What happens to the oxidation state of vanadium when it reacts with sulfur dioxide?

  It is reduced from +5 to +4
• Why must vanadium pentoxide be returned to its original oxidation state after acting as a catalyst?

  Because a catalyst cannot be used up or changed by the chemical reaction
• What does vanadium pentoxide react with to return to its +5 oxidation state?

  Half a mole of oxygen
• What is the role of a catalytic converter in cars?

  • Converts carbon monoxide to carbon dioxide
  • Reduces nitrous oxides to nitrogen gas
  • Uses platinum, palladium, or rhodium nanoparticles
• What harmful substances are produced from the incomplete combustion of hydrocarbon fuels in cars?

  Carbon monoxide and nitrous oxides
• Why do fuel companies remove lead and sulfur from fuels?

  To prevent poisoning of the catalyst in the catalytic converter
• What catalyst is used in the Haber process for ammonia production?

  Iron
• What happens when a catalyst becomes poisoned?

  It becomes less efficient and cannot work properly
• What is the analogy used to explain catalyst poisoning in the study material?

  The bonding of carbon monoxide to hemoglobin in red blood cells
• What is the effect of a poisoned catalyst on industrial costs?

  It can lead to increased costs due to reduced efficiency
• What is homogeneous catalysis?

  • Catalyst is in the same phase as the reactants
  • Often involves a catalyst that is dissolved in an aqueous solution
  • Requires the formation of an intermediate species