OCR A Level Chemistry Module 3 Exam Questions and Mark Scheme – Revision
Essential
1st shell - ✔✔✔-1s
2nd shell - ✔✔✔-2s 2p
3rd shell - ✔✔✔-3s 3p 3d
4th shell - ✔✔✔-4s, 4p, 4d, 4f
activation energy - ✔✔✔-the minimum amount of energy required to start a chemical reaction
Average bond enthalpy - ✔✔✔-The mean energy needed for 1 mole of a given type of gaseous
bonds to undergo homolytic fission
Bleach formation - ✔✔✔-Cl2(aq) + 2NaOH(aq) = NaCl(aq) + NaClO(aq) + H2O(l)
Boltzmann distribution - ✔✔✔-The distribution of energies of molecules at a particular
temperature, usually shown as a graph.
Boltzmann distribution- temperature increase - ✔✔✔--kinetic energy of all molecules increases
-distribution flattens and shifts to the right
-more collisions take place
-higher proportion of molecules have an energy greater than the activation energy
Boltzmann distribution-catalysts - ✔✔✔--lower activation energy
-more particles will be above the activation energy barrier
-more successful collisions
, OCR A Level Chemistry Module 3 Exam Questions and Mark Scheme – Revision
Essential
Collision theory - ✔✔✔-For a reaction to occur, the particles must collide, they must collide
with the appropriate orientation, and they must collide with sufficient energy.
Disproportionation - ✔✔✔-The same element in a reaction is reduced and oxidised
Dynamic equilibrium - ✔✔✔-condition of continuous, random movement of particles but no
overall change in concentration of materials
-closed system
Economic importance of catalysts - ✔✔✔--they lower the energy demands, by doing so they
reduce costs
-less carbon dioxide emissions
-improves yields
Effect of catalyst on rate of reaction - ✔✔✔-The presence of a catalyst will increase the rate of
reaction as the reactant particles are more likely to collide at the correct angle. This means that
more successful collisions are likely to occur per unit time in the presence of a catalyst
compared to not having a catalyst present.
Effect of concentration on equilibrium - ✔✔✔--equilibrium shifts in the direction that decreases
the concentration
Effect of concentration on rate of reaction - ✔✔✔-Increasing the concentration of a reactant
(i.e. having more reactant particles per unit volume) will increase the rate of reaction as there
are more particles available to react at any one time, therefore more successful collisions are
likely to occur per unit time.
Essential
1st shell - ✔✔✔-1s
2nd shell - ✔✔✔-2s 2p
3rd shell - ✔✔✔-3s 3p 3d
4th shell - ✔✔✔-4s, 4p, 4d, 4f
activation energy - ✔✔✔-the minimum amount of energy required to start a chemical reaction
Average bond enthalpy - ✔✔✔-The mean energy needed for 1 mole of a given type of gaseous
bonds to undergo homolytic fission
Bleach formation - ✔✔✔-Cl2(aq) + 2NaOH(aq) = NaCl(aq) + NaClO(aq) + H2O(l)
Boltzmann distribution - ✔✔✔-The distribution of energies of molecules at a particular
temperature, usually shown as a graph.
Boltzmann distribution- temperature increase - ✔✔✔--kinetic energy of all molecules increases
-distribution flattens and shifts to the right
-more collisions take place
-higher proportion of molecules have an energy greater than the activation energy
Boltzmann distribution-catalysts - ✔✔✔--lower activation energy
-more particles will be above the activation energy barrier
-more successful collisions
, OCR A Level Chemistry Module 3 Exam Questions and Mark Scheme – Revision
Essential
Collision theory - ✔✔✔-For a reaction to occur, the particles must collide, they must collide
with the appropriate orientation, and they must collide with sufficient energy.
Disproportionation - ✔✔✔-The same element in a reaction is reduced and oxidised
Dynamic equilibrium - ✔✔✔-condition of continuous, random movement of particles but no
overall change in concentration of materials
-closed system
Economic importance of catalysts - ✔✔✔--they lower the energy demands, by doing so they
reduce costs
-less carbon dioxide emissions
-improves yields
Effect of catalyst on rate of reaction - ✔✔✔-The presence of a catalyst will increase the rate of
reaction as the reactant particles are more likely to collide at the correct angle. This means that
more successful collisions are likely to occur per unit time in the presence of a catalyst
compared to not having a catalyst present.
Effect of concentration on equilibrium - ✔✔✔--equilibrium shifts in the direction that decreases
the concentration
Effect of concentration on rate of reaction - ✔✔✔-Increasing the concentration of a reactant
(i.e. having more reactant particles per unit volume) will increase the rate of reaction as there
are more particles available to react at any one time, therefore more successful collisions are
likely to occur per unit time.
