AP Chemistry Unit 5.1 Reaction Rates

Reaction Rates

  • Spontaneous reactions: reactions that will happen but we cant tell how fast
  • Kinetics: the study of the rates of a chemical reaction
  • Can determine the coeffiecents of the chemical equation when given graph of concentration vs time by doing –.
  • Ex:  
    • The rate of disappearance of A is equal to the rate of appearance of B and ½ the rate of appearance of C

Factors that Affect Reaction Rates

  • According to the collision theory, the rate of a reaction is influenced by anything that affects the number or force of collisions
    • Increase collisions = increase rate
  • Reactant concentration
    • Increasing concentration causes an increase in the frequency of collisions which increases reaction rates (except for zero-order reactions)
  • Increasing temperature: increasing the temp increases the frequency of collisions and the number of particles that have enough kinetic energy to collide and overcome the AE and form products
    • Increase temperature = increases number of successful collisions
  • Pressure: For reactions involving gases, increasing pressure increases the collisions between reactants,
  • Particle size and increasing surface area
    • The smaller the particle size with more sides, the larger the surface area for a given mass of particle
    • Increase surface area → more collisions
  • Catalysts: A catalyst will change the value of K because the activation energy changes
    • The value of the rate constant is also dependent on the activation energy
  • Inhibitor: a substance that decreases the rate of a reaction by increasing Ea
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