Kinetics

• Collision theory:

  • chemical reactions occur when particles of substances collide
  • Successful reaction —> collisions must have energy greater/equal to the activation energy of the reaction & correct particle orientation
• Reaction Conditions:

  conditions can be changed to increase the likelihood of a collision occurring with sufficient energy to react in order to increase rate
• Maxwells - boltzmann distribution:

  not all molecules in a substance have the same amount of energy
• Changing conditions alters shape of curve

  • Number of particles with greater energy than the activation energy is different
  • Total area under curve = total number of molecules ( remains constant)
• Effect of temperature on energy:

  • thermal energy is transferred to substance —> converted to kinetic energy so molecule more faster & further
  • More collisions have energy greater than activation energy
  • Increases rate of reaction as more collisions of greater energy occur at a given time
• Maxwell - botMann curve when temperature is increased:

  • at increased temp —> distribution shifts to the right
  • Greater proportion of molecules have energy greater/equal to activation energy

  
• Effect of concentration & pressure on energy:

  • concentration/ pressure increased —> more particles of a substance occur in a given volume
  • Collisions between molecules are more likely & chance of collision occurring with energy > activation energy increases
  • Rate of reaction increases
  • Distribution shifts to the right
• Effect of catalysts on energy/ collisions:

  • increases rate of reaction without being used up
  • Provides an alternative reaction pathway that requires a lower activation energy for reaction to occur
  • Distribution curve is unchanged
  • Position of activation energy is shifted left —> greater proportion of molecules have sufficient energy to react

  
• Maxwell- Boltzmann distribution curve:

  
• Le Chateliers principle:

  • if a system at equilibrium is subjected to a change in conditions, the system will adjust itself to counteract that change & restore a new equilibrium
• Dynamic equilibrium:

  • the forward & reverse reactions are occurring at the same rate—> results in concentrations of reactants & products remaining constant over time
  • No net change in amount of reactant & products —> continuously occurring, rates are equal, stable conditions
  • Can be affected by changes in conditions which shifts balance
• Shift in equilibrium during temperature change:

  • shifts in direction that absorbs heat to counteract the increase in temperature
  • Yield of side shifted to decreases
• Successful reaction:

  • collisions Must have energy greater/ equal to the activation energy
  • Particle orientation must be correct