kinetics

• Rate of reaction


  Change in concentration of a substance in unit time
• Factors that affect the rate of reaction

  • Increase of temperature
  • Increasing concentration of solution
  • Increasing pressure of a gas reaction
  • Increasing surface area
  • Catalyst
• Increase of temperature


  • Increases speed of molecules
  • Increases energy and number of collisions for second
  • More particles have energy greater than or equal to than the activation energy
• Increasing concentration of solution

  • Increases rate of reaction
  • As the reaction proceeds the reactants are used up and their concentration falls
• Increasing pressure of a gas reaction

  • More particles in a given volume so more energy so faster rate of reaction as more collisions per second
• Increasing surface area


  • More particles are available to react so faster rate of reaction due to more collisions per second
• Catalyst


  • Changes rate of reaction without being chemically changed itself
• The graph starts at zero (0,0) because no particles have zero energy. There are a range of energies due to particles
• The graph is asymptotic because there is always a chance that a particle has a vast amount of energy
• Catalyst


  • Speeds the rate of reaction without getting used up
  • Provides an alternative route to lower activation energy
  • At a lower activation energy more particles have energy greater than or equal to the activation energy giving more successful collisions per second meaning faster rate of reaction
• Homogeneous catalyst


  Catalyst is in the same state as the reactants
• Heterogeneous catalyst


  The catalyst is in a different state as its reactants
• How a surface catalyst works

  1. The gas molecules are far apart so the surface brings them together so they can react

  2. The catalyst has active site which absorb the gas molecules

  3. The gases react and are then desorbed from the surface

  4. The active site are then available again

  5. After a while the active sites gets poisoned and the catalyst needs replacing
• How to monitor the rate of reaction

  • Colour change using a colorimeter
  • Measure the gas made overtime
  • Time taken for solid to disappear
  • Temperature change
• Order of Reaction - The sum of the exponents of the concentrations of all the reactant species in the rate law.
• Rate law - The relationship between the rate of a chemical reaction and the concentration of its reacting species, expressed as an algebraic function.
• Zero-order reaction - A type of chemical reaction where the rate of reaction does not depend on the concentration of any reactant or product involved.
• The rate equation is the mathematical expression that relates the initial reaction rate to the concentrations of reactants.