Topic 9- KINETICS 1

• Rate of reaction = change in concentration (mol dm-3) / time (s) units: mol dm -3 s-1
• The minimum amount of energy that particles must have to react is the activation energy
• Collision theory: reacting particles collide with each other and with sufficient energy. Molecules must collide with the correct orientation (collide with the rightt molecule).
• Factors that increases the chance of effective collisions increases the rate(speed) of reaction:

  • Increased S.A (for solids)
  • Increased conc. (For solution)
  • Increased pressure (for gases)
  • Increased temperature
  • Use of catalyst
• INCREASED S.A: the smaller particle size, the Increased S.A, rate of reaction Increases bc the frequency (n' of collisions per sec) of collisions increases
• INCREASING CONCENTRATION (n' of moles in a volume):

  • If the conc. Of reactants increases, there are more moles of reactants in a given volume
  • The frequency of collisions increases
  • So the frequency of successful collisions increases
  • So the rate of reaction increases
• INCREASING PRESSURE:

  • if pressure increases, more particles in a given volume
  • Frequency of collisions between particles increases
  • So the rate of reaction increases
• INCREASING TEMPERATURE:

  • The rate of reaction increases
  • because... particles collide more often - frequency of collisions increases
  • And because.... particles collide withh more energy (MOST IMPORTANT FACTOR)
  • so, more particles have energy higher than activating energy and can react successfully.
• MEASURING RATE OF REACTION:

  • Measure how fast the products are formed or reaction are used up - either measure:
  • Average rate
  • How rate changes with time e.g. measure time taken for a piece of Mg to disappear
• ADDING A CATALYST:

  • Increases the rate of reaction by providing an alternative path/mechanism with a lower activation energy.
  • Catalyst are not used up in the reaction
  • Catalysts are important in industrial processes to reduce costs
• • Homogeneous catalyst: in the same phase as reactants (same physical state) form a intermediate compound with the reactants
  • Heterogeneous catalyst: are in different phase to reactants (e.g. soldi catalyst and gas reactants) promote reactants through their active sites.
• In heterogeneous catalyst- the catalyst provide S.A.

  • Catalysts is used bc gas is spread out, so it stretches the H-H bonds and get it this react with the C=C bond

  
• MEASURING RATE OF REACTION: as time increases, mass decreases bc. CO2 (g) escapes from the top. The cotton wool to prevent the acid escaping bc. there's fizzing (loss of mass). CaCO3(s) + 2HCL(aq) ----CaCL2 (aq) + CO2(g) + H2O(l)

  
• MEASURING RATE OF REACTION: measuring the rate of reaction is done by measuring volume of gas produced over time. As time goes on, gredient decreases, so rate decreases.

  
• RATE GRAPHS AND REACTANT CONCENTRATION

  A) reactant

  B) rate

  C) gradient

  D) fast

  E) shallow

  
• RATE OF REACTION GRAPH: in GREEN LINE with slower reaction- has the same amount of product due to: lower temperature and smaller S.A. when gradient=0, REACTION HAS STOPPED AS ALL REACTANTS HAS BEEN USED UP

  A) slower

  B) used up

  
• EXOTHERMIC, ENDOTHERMIC, AND WITH/WITHOUT CATALYST

  A) catalyst

  B) -ve

  C) +ve

  D) intermediate

  
• MAXWELL-BOLTZMANN DISTRIBUTION OF ENERGY: effect of temperature, effect of catalyst

  A) doubles

  B) with energy

  C) broadens

  D) energy

  E) shifts

  F) under

  G) activation energy

  H) catalyst

  I) 10

  
• MAXWELL-BOLTZMANN DISTRIBUTION OF ENERGY

  A) fraction

  B) changes

  C) same

  D) distribution

  E) n' of particles

  F) collide

  G) react

  H) react

  
• Explain the difference in the rate of reaction when smaller marble chips are used instead of the large marble chips. - the smaller the marble chips have higher S.A, so faster rate, so higher frequency of collisions
• give a reason why the volume of CO2 collected in the experiment is less than 90cm3. - some CO2 dissolved in the acid OR some gas will escape before bung is replaced.
• give a reason why the mineral was crushed before being added to the acid. - for faster reaction as S.A in increased