AQA A-Level Chemistry (new spec) 1.5 Kinetics

• Explain how increasing concentration effects the rate of reaction. [3]

  More particles per unit volume

  More frequent collisions

  ROR increases
• What is the effect of increasing temperature on the rate of reaction?

  Particles have increased Ek

  Many more particles have energy greater or equal to activation energy

  Many more successful collisions

  Significant increase in the ROR
• What is the collision theory?

  Reactions can only occur when collisions take place between particles when they have sufficient energy
• Define activation energy

  The minimum energy needed for particles to collide to start a reaction
• What does the Maxwell Boltzmann distribution show?

  The spread of energies that molecules of a gas or liquid have at a particular temperature
• Why should the energy distribution go through the origin on the graph?

  There are no molecules with no energy
• What is the Emp?

  Most probable energy
• Where is the Emp line on the graph?

  From the peak down to the X-Axis
• What does the area under the curve represent?

  The total number of particles present
• Why should the energy distribution never meet the x-axis?

  Because there is no maximum energy for molecules
• What is the label for the y-axis?

  Number of molecules within a given energy
• What is the label for the x-axis?

  Energy
• What happens to the particles when the temperature is increased?

  More particles will have energy greater than the activation energy
• What does Ea stand for?

  Activation energy
• What happens to the peak of the Maxwell Boltzmann distribution when the temperature is increased?

  It moves to a higher energy with a lower height
• What happens to the proportion of molecules exceeding the activation energy when the temperature is increased?

  The proportion of molecules increases
• What happens to the Emp and mean energy when the temperature increases?

  They shift to high energy values
• Why should the total area under the curve remain constant when the temperature is increased?

  The total number of particles stay constant when temperature is increased
• In terms of collision theory, what happens to the particles when temperature is increased?

  The energy of the particles increases, meaning they collide more frequently with energy greater than the activation energy. More collisions = more reactions
• What happens to the range of energies of the molecules when the temperature is higher?

  The range of energies is wider
• In terms of the collision theory, what happens to the particles when the concentration is increased?

  There are more particles present so the particles collide more frequently
• What happens to the mean and the Emp when the concentration is increased?

  They stay the same
• Will the area under the curve differ when the concentration is increased?

  Yes because there are more particles, meaning the peak will be higher
• In terms of the collision theory, what happens to the particles when the surface area is increased?

  It causes collisions to occur more frequently, increasing the rate of reaction
• What do catalysts do?

  They increase reaction rates by providing an alternative route with a lower activation energy?
• Are catalysts ever used up?

  No
• What is Ec?

  Activation energy with a catalyst
• What happens to the proportion of molecules exceeding the activation energy when a catalyst is present?

  The proportion increases as the activation energy is lower
• What happens to the rate of reaction when a catalyst is introduced?

  It increases
• Define the rate of reaction

  The change in concentration of a substance in unit time.
• What is the initial rate?

  The rate at the start of a reaction