Energy Change & Rates of Reaction

Question 1

heat of reaction

Question 2

exothermic reactions

Question 3

endothermic reactions

Question 4

activation energy

Question 5

activated complex

Question 6

Draw and interpret potential energy profile graphs of catalysed
and uncatalysed endothermic reactions and exothermic reactions
(with reactants, products, activation energy, activated complex
and ΔH labelled)

Question 7

reaction rate

Question 8

average and instantaneous reaction

Question 9

factors that affect the rate of chemical reactions
(Nature of reacting substances, surface area of a solid,
concentration of a solution, pressure of a gas, temperature
and catalyst)

Question 10

catalyst

Question 11

The collision theory

Answer 11

the collision theory is a model that explains that
a reaction will only proceed when reactant particles collide
effectively. An effective (or successful) collision is one in
which the colliding reactant particles have:
- the correct orientation
- sufficient energy, i.e. kinetic energy equal to or greater
than the activation energy

Question 12

Explain in terms of the collision theory that reaction rate is
directly proportional to the number of effective collisions per
unit time

Question 13

Explain in terms of the collision theory how the various
factors affect the rate of chemical reactions

Question 14

Suggest and explain suitable experimental techniques for
measuring the rate of a given reaction including the
measuring of gas volumes, turbidity (e.g. precipitate
formation), change of colour and the change of the mass of
the reaction vessel

Question 15

Apply collision theory to explain the changes in the
distribution of molecular energies (number of particles
against their kinetic energy, i.e. Maxwell-Boltzmann
distribution) due to changes in temperature, concentration
of reactants and the presence of a catalyst

Question 16

Use any other suitable graph (including e.g. energy profile
graph, rate vs time or amount vs time) to show how
changing concentration, pressure, surface area, or adding a
catalyst affects the rate of reaction