Reaction Mechanisms and Collision Theory
Pg 243 #3, 4 a and c , 6, 7, 9 abcde, 10
Answers
#3 a) 4 b) 3 c) 8 d) 7 e) 5
#4 a) 1) 3 steps 2) 1st step = 400 kJ/mol, 2nd step = 100 kJ/mol, 3rd step
= 550 kJ/mol
3) The third step will be the rate determining step, since the
activated complex of this step is
500kJ/mol, while the other two have a lower energy. Therefore
the reaction rate of the third
step will be the slowest.
c) 1) 2 steps 2) 1st step = 40 kJ/mol, 2nd step = 80 kJ/mol
3) The second step will be the rate determining step since the
activated complex of this step is
100 kJ/mol, while the other has a lower energy level.
Therefore the reaction rate of the second
step will be the slowest.
#6 a) The rate-determining step will be the slow reaction since the overall
reaction cannot go faster
than its slowest reaction. The energy level of its activated
complex will be higher.
b) There would be less x than y, more y than z and more final
product than z.
# 7 Will post in class
#9 a) The second only
b) The first and the third.
c) The third
d) Endothermic
e) The first or the second
#10 The mixture of methane and oxygen does not react immediately, since the
particles do not have sufficient energy to form the activated complex and allow
the reaction.
Factors Affecting Reaction Rate
Pg 243 #5, 8, 9f
Pg 250 #1, 3, 4, 6
Pg 258 #1
Pg 267 #1, 4, 5
Pg 243
#5 a) The rate increases. By doubling the number of particles, the number
of effective collisions doubles and the reaction rate will double.
b) The rate increases. By doubling the pressure, the effect is the same as
if the volume were reduced, therefore there will be two times less space for the
molecules, and two times more effective collisions. The reaction rate will
double.
c) The rate decreases. If the temperature is decreased, the kinetic energy
of the particles will decrease and therefore, there will be fewer effective
collisions. The reaction rate will decrease.
#8 No. An increase in the temperature does not affect the activation
energy. It increases the number of effective collisions and therefore, the
reaction rate. The activation energy will be attained more quickly, but it will
be at the same energy level.
#9f Several possible answers.
Examples:
-Increase the number of effective collisions by increasing the
concentration of the substances in the third reaction
-Add a catalyst
Etc...
Pg 250
#1 a) 1
b) This reaction will be slower than the other reactions that only involve
reactants in the gas phase, but not slower than those that involve reactants in
the liquid or solid phase.
c) 3, 1, 4, 2
#3 Reaction c), because the reactants are aqueous ions. In this case, the
reactions occur almost instantaneously.
#4 Order: a, d, c,b
Reaction a will be fastest because it involves aqueous ions, while reaction
b will be slower because it is heterogeneous in which the reactants are in two
different phases. Reactions c and d will have rates intermediate to those of
reaction a and b. Reactions c and d both occur in the gas phase but reaction c
has more bonds to break, therefore it will be slower than reaction d.
#6 a) They occur at the same rate since it is the same reaction. If
reaction 2 had C24H50 in the liquid phase, it would be faster.
b) It is reaction 2, since in C12H22 there are double or triple bonds
between the carbon atoms and more energy is required to break these bonds than
single carbon-carbon bonds.
Pg 258
#1 The more molecules there are, the greater the number of effective
collisions. The greater the concentration, the more molecules there will be per
unit of volume, therefore a greater number of effective collisions and
consequently, a higher reaction rate.
Pg 267
#1 The decrease of the temperature to -20 deg C reduces the kinetic energy
of the molecules and the rate of growth of micro-organisms. Therefore, food will
decompose much more slowly.
#4 No, the addition of a catalyst in a reaction decreases the activation
energy, but does not play a role in the final concentration of the
products.
#5 a) Reaction 2. The substances in the three reactions are all in the same
phase, but reaction 2 has fewer bonds to break than the other reactions.
Therefore, it will be fastest.
b) Reaction 3. It has the most bonds to break
Nature of Reactants worksheet
1. a) No effect b) Increase c) No effect d)
Decrease
2. The first because propane is in the gas state, same state as
oxygen.
3. The second is fastest because methane (CH4) has fewer bonds
compared to wax (C25H52).
4. C, A, B
5. B, A, D, C
Collision Theory Worksheet
Front side
1. Lower temperature in the fridge will reduce the kinetic energy of
the particles leading to less effective collisions and a slower reaction
rate.
2. Concentration - increases the number of particles, increases the
number of effective collisions and the reaction rate.
Temperature - increase the temperature and the kinetic energy
increases, increases the number of collisions and the reaction rate.
Surface Area - increasing the surface area, increases the number of
particles available for effective collisions, and the rate increases.
Nature of Reactants - Homogeneous, small, ionically bonded reactants
which have few bonds will have more effective collisions and the rate
increases.
Catalyst or Inhibitors - Catalysts will decrease the activation
energy barrier which reduces the minimum energy required in the collisions
of the reactants to form products. Inhibitors do the opposite.
Back side
1. Concentration, Temperature, Surface Area, Catalyst
2. Increasing the surface area will increase the number of particles
that are available for a reaction to occur, increasing the number of effective
collisions. This will work for reactants that are in the solid state,
where the substance can be crushed to form a powder and increase the surface.
As well as for liquid/aqueous reactant that can be placed in a container
that will increase the surface area. In each situation there will be more
particles available for effective collisions.
3. a) Increases the number of particles, increases effective
collisions, increases rate.
b) Decreases the kinetic energy, decreases effective collisions, decreases
rate.
c) Surface Area - Increases the number of particles available for reaction,
increases effective collisions, increases rate.
d) Decreases the number of particles, decreases effective collisions,
decreases rate.
4. a)Increases the number of particles, more effective collisions,
increases rate.
b) Decreasing temp, lowers kinetic energy, reduces number of effective
collisions, decreases rate.
c) Increasing temp, increases kinetic energy, more effective collisions,
increases rate.
d) Increasing
temp, increases kinetic energy, more effective collisions, increases
rate.
e)
Surface area - Increases
the number of particles available for reaction, increases effective collisions,
increases rate.
f)
Addition of a catalyst will increase the rate of reaction by lowering the
activation energy barrier by providing a surface for the particles to react
together (makes it easier for particles to react).
g)
Nature of the Reactants - Dissolving the particles will cause them to be in the
same state (homogeneous) which will make it easier for them to
react.
5.
Since the reaction happens immediately as soon as the surface is exposed
it can be said that this is a spontaneous reaction with a very low activation
energy barrier.
6.
The lower temperature would lead to the formation of more product but it
would take too long in order for this to occur. Lower temperatures reduces
the kinetic energy and the number of effective collisions and the rate. In
order to get product faster the reaction is carried out at a higher temperature
where there is higher kinetic energy and more effective collisions.
To fully understand this problem we will learn about equilibrium factors in
the next topic (in March). The key thing to note is that the reactants are
continuously added to the system and product is continuously removed, this
allows a constant production of ammonia at a fast rate due to the high
temperature conditions.
MID YEAR REVIEW
See attachments below
The review is the file: numérisation0128
The answers are given in the other file: numérisation0129
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numrisation0129.pdf | |
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