kinetics 1

• What is the fundamental requirement for a chemical reaction to occur according to Collision Theory?

  Reactant particles must collide.
• What must be true about the energy of collisions for a reaction to occur successfully?

  The collisions must have energy greater than or equal to the activation energy.
• What is the definition of activation energy?

  It is the minimum amount of energy required for two particles to react.
• What does the Maxwell-Boltzmann distribution illustrate about molecules in a substance?

  It shows that not all molecules have the same amount of energy.
• How does changing reaction conditions affect the Maxwell-Boltzmann distribution curve?

  It alters the shape of the curve, changing the number of particles with energy greater than the activation energy.
• What does the total area under the Maxwell-Boltzmann distribution curve represent?

  It represents the total number of molecules in the sample.
• How do reaction conditions impact the likelihood of successful collisions?

  They can be altered to give the particles more energy, increasing the likelihood of collisions with sufficient energy to react.

  
• How can the rate of reaction be calculated from empirical data?

  It can be calculated from data plotted on graphs.
• What does the gradient of a concentration-time graph represent?

  It represents the rate of reaction at a given point.
• How can the initial rate of reaction be found on a concentration-time graph?

  By drawing a tangent to the curve when time = 0.
• What happens to the rate of reaction when a substance is heated?

  The thermal energy is converted to kinetic energy, causing molecules to move faster and collide more often.
• How does increasing temperature affect the Maxwell-Boltzmann distribution?

  It shifts the distribution to the right, increasing the proportion of molecules with energy greater than or equal to the activation energy.

  
• What effect does increasing concentration have on the rate of reaction?

  It increases the likelihood of collisions by packing more molecules into the same volume.
• How does increasing pressure affect gas reactions?

  It packs molecules closer together, increasing the likelihood of collisions.
• What remains unchanged when concentration or pressure is increased?

  The energy of the individual particles remains unchanged.
• What happens to the shape of the Maxwell-Boltzmann distribution when concentration or pressure is increased?

  The shape of the distribution does not change.
• How does increasing the surface area of a reactant affect the rate of reaction?

  It increases the number of exposed reactant particles, leading to more frequent successful collisions.
• What is the role of a catalyst in a chemical reaction?

  A catalyst increases the rate of reaction without being used up by providing an alternative reaction path with lower activation energy.

  
• How does the Maxwell-Boltzmann distribution change when a catalyst is used?

  The shape of the distribution remains unchanged, but the position of the activation energy shifts to the left.
• Why are catalysts used in industry?

  They lower the energy costs of the reaction process and allow lower temperatures and pressures to be used while achieving the same rate of reaction.
• What does the energy profile of a catalyzed reaction show?

  It shows a dip representing the intermediate formed during the reaction, which is less stable than the reactants and products.

  
• What are heterogeneous catalysts?

  They are catalysts that are in a different phase or state to the species in the reaction.
• Why do transition metals make good catalysts?

  They have variable oxidation states that allow for electron transfer to produce a reactive intermediate.
• In the Haber Process, what type of catalyst is used?

  A solid iron catalyst.
• What is the process of adsorption in relation to solid catalysts?

  It involves adsorbing molecules onto an active site on the surface of the catalyst, increasing proximity and weakening covalent bonds for easier reactions.

  
• How do active sites on a catalyst affect reaction rates?

  They increase the proximity of molecules and weaken covalent bonds, facilitating reactions.
• What are the key factors affecting the rate of reaction?

  • Temperature: Increases kinetic energy and collision frequency.
  • Concentration: Increases the number of molecules in a given volume.
  • Pressure: Increases the closeness of gas molecules.
  • Surface Area: Increases the number of exposed particles.
  • Catalysts: Lower activation energy and provide alternative pathways.

  
• What is activation energy (E​a​)?

  Minimum amount of kinetic energy the particles need to react.
• What is the role of a catalyst in a chemical reaction?

  A catalyst provides an alternative reaction route of lower activation energy and speeds up the reaction.
• How does a catalyst behave at the end of a reaction?

  A catalyst is chemically unchanged at the end of the process.
• What is a heterogeneous catalyst?

  A heterogeneous catalyst is in a different phase from the reactants.
• In which type of reactions is a heterogeneous catalyst typically used?

  In gas phase reactions to provide a surface for the reaction.
• Give an example of a heterogeneous catalyst.

  A transition metal used in the hydrogenation of alkenes.
• What is a homogeneous catalyst?

  A homogeneous catalyst is in the same physical state as the reactants.
• Provide an example of a homogeneous catalyst.

  Acid-catalysed esterification.
• What does the Maxwell-Boltzmann distribution represent?

  A distribution of energy among the molecules of a gas in a closed system.
• What does the area under the Maxwell-Boltzmann distribution graph indicate?

  The area under the graph indicates the number of particles.
• How does increasing temperature affect the Maxwell-Boltzmann distribution?

  At higher temperatures, the average energy increases and the maximum of the curve shifts.
• What happens to the proportion of molecules with energy equal to or greater than activation energy as temperature increases?

  There is a higher proportion of molecules with energy equal to or greater than activation energy.

  
• What is the starting point of the Maxwell-Boltzmann distribution graph?

  The graph starts at (0,0) - no molecules have zero energy.