Kinetics

Cards (30)

  • What must reactant particles do for a chemical reaction to occur?
    Collide with one another
  • Why do not all collisions result in a reaction?
    Only a fraction lead to product formation
  • What is activation energy (E<sub>a</sub>)?
    The minimum energy required for a reaction
  • What happens if particles collide with energy less than E<sub>a</sub>?
    They bounce off without reacting
  • What is the progress of a chemical reaction in terms of energy?
    • Energy barrier must be overcome
    • Bonds are stretched
    • New bonds formed, releasing energy
  • What does a Maxwell-Boltzmann distribution illustrate?
    The spread of gas molecule speeds
  • How do gas molecules move in a container according to Maxwell-Boltzmann distribution?
    They move at different speeds
  • What does the peak of a Maxwell-Boltzmann curve represent?
    The most likely energy of a molecule
  • What does the area under the Maxwell-Boltzmann curve represent?
    All the gas molecules
  • What happens to the Maxwell-Boltzmann distribution curve at higher temperatures?
    It flattens and broadens
  • How does temperature affect the proportion of molecules with activation energy?
    More molecules have energy ≥ E<sub>a</sub>
  • What is the effect of higher concentration or pressure on reaction rate?
    Increases likelihood of collisions
  • How does the shape of the Maxwell-Boltzmann distribution curve change with concentration?
    The curve height increases
  • What do catalysts do to the activation energy of a reaction?
    They lower the activation energy
  • How do catalysts affect the rate of reaction?
    They increase the rate of reaction
  • What is the Haber process used for?
    Synthesizing ammonia (NH₃)
  • What role does the iron catalyst play in the Haber process?
    It lowers the activation energy
  • What are the two main types of catalysts?
    • Homogeneous catalysts: same phase as reactants
    • Heterogeneous catalysts: different phase than reactants
  • What is an example of a homogeneous catalyst?
    Acid catalysis in esterification
  • What is an example of a heterogeneous catalyst?
    Iron in the Haber process
  • What do catalytic converters do in cars?
    Convert harmful gases into less harmful substances
  • How do catalysts affect the overall enthalpy change (ΔH) of a reaction?
    They do not alter the overall ΔH
  • How does a lower activation energy affect the proportion of molecules that can react?
    More molecules have enough energy to react
  • What is the rate of reaction?
    • Measures how quickly reactants are consumed
    • Measures how quickly products are formed
  • How does the concentration of reactants change during a reaction?
    It decreases over time
  • What happens to the reaction rate as reactant concentrations decrease?
    The reaction rate slows down
  • What is the reaction between sodium thiosulphate and hydrochloric acid?
    Na<sub>2</sub>S<sub>2</sub>O<sub>3</sub> + 2HCl → 2NaCl + SO<sub>2</sub> + S + H<sub>2</sub>O
  • What visual change indicates the progress of the reaction between sodium thiosulphate and hydrochloric acid?
    The solution becomes cloudy
  • What should be recorded during the reaction experiment?
    The time for the cross to disappear
  • How does temperature affect the time for the cross to disappear?
    Higher temperatures decrease the time