CHAPTER 1 : THE RATE OF REACTION
Concept Map
Energy Profile Diagram
Activation energy
Effective collision
Collision theory
Factors affecting the
rate of reaction
RATE OF REACTION
Application
Finding rate of reaction
Industries
Average rate of reaction
Everyday life
Rate of reaction at a
given time
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Definition of the rate of reaction

Rate of reaction is the speed at which reactants are converted into products in a
chemical reaction.

Rate of reaction = change in selected quantity
time taken
Measuring rate of reaction
Average rate of reaction in the first t2 seconds
= volume of gas collected in the first t2 second (cm3)
time taken (s)
3 -1
= V2 cm s
t2
Volume of gas (cm3)
Average rate of reaction in the t2 seconds
Volume of gas collected in the first t2 sec = V2
Volume of gas collected in the first t1 sec = V1
V3
V2
V1
a
Volume of gas collected in the t2 sec
= V2 – V1 = V cm3
b
Time taken for the reaction = t2 – t1 = t s
t1 t2 t3
Average rate of reaction in the t2 sec = V
t
t4
cm3s-1
Time (s)
The overall average rate of reaction
Time taken for the reaction to be complete = t4 s
Total volume of gas collected at t4 s = V3
Overall average rate of reaction = V3
t4
cm3s-1
Instantaneous rate of reaction / the rate of
reaction at t3 sec
= gradient of the curve at t3 sec = a cm3s-1
b
2
Worksheet 1
1. The following figure shows the graph of carbon dioxide, CO2 gas produced when an excess
of calcium carbonate, CaCO3 reacts with 40 cm3 of 0.1 moldm-3 hydrochloric acid, HCl.
(a) Calculate the
(i)
Average rate of reaction in the first 10 sec
(ii)
Average rate of reaction in the 30 sec
(iii)
Overall average rate of reaction
(b) Explain your answer to part (a) with respect to the concentration od hydrochloric acid.
3
2. The following table shows the volume of a gas collected from an experiment.
Time (s)
Volume of gas (cm3)
0
0
30
17
60
29
120
36
150
36
Calculate th average rate of reaction for
(a) the first 60 seconds
(b) the overall reaction
3. The decrease in mass of a reaction mixture is recorded in the following table.
Time (min)
Mass of reaction mixture (g)
0
2.90
1
1.90
2
1.25
3
0.75
4
0.40
(a) Draw a graph of mass of reaction mixture against time.
(b) Calculate the rate of reaction at the
(i) start of the reaction
(ii) the third minute.
4
5
0.10
Factors effecting the rate of reaction
Effect of surface area
Effect of concentration
Eq : ……………………………………………………….
Eq : ……………………………………………………….
Volume of gas (cm3)
Concentration (moldm-3)
Expt 1 : CaCO3 chips
Expt 2 : CaCO3 powder
Expt 2
Expt 1
Time (s)
 The higher the concentration, the …………………
the time taken.
 The concentration is ………………………………...
to the time taken.
Time (s)
 The curve of expt 2 is ……………… than expt 1.
 The rate of reaction of expt 2 is …………………
than expt 1
 The smaller the size of reactants,
the …………………………. the total surface area,
the …………………………. the rate of reaction.
Concentration (moldm-3)
1/ time (s-1)
Effect of temperature
Eq : ……………………………………………………….
 1/ time is ……………………………………………..
 The concentration is ………………………………..
to the 1/time
 The ………………………….. the concentration,
the …………………… the rate of reaction.
Concentration (moldm-3)
Effect of catalyst
Time (s)
Eq : ……………………………………………………….
 The higher the temperature, the ...…………………
the time taken.
 The temperature is ………………………………...
to the time taken.
Volume of gas (cm3)
Expt 1 : with catalyst
Expt 2 : without catalyst
Expt 1
Temperature (oC)
Expt 2
Time (s)
 The curve of expt 2 is ……………… than expt 1.
 The rate of reaction of expt 2 is …………………
than expt 1
 The presence of catalyst, will ……………………...
the rate of reaction.
1 / time (s-1)
 1/ time is ……………………………………………..
 The temperature is ..………………………………..
to the 1/time
 The ………………………….. the temperature,
the …………………… the rate of reaction.
5
Worksheet 2
1. State five factors which affect the rate of reaction.
(i) …………………………………………………… (ii) ……………………………………………….
(iii) …………………………………………………… (iv) ………………………………………………
(v) ……………………………………………………..
2. Draw a diagram to show the set up of the apparatus in an experiment to investigate the rate
of reaction between calcium carbonate and dilute hydrochloric acid.
3. Sketch a graph for the total volume of gas collected against time.
4. State a hypothesis for investigating the effect of temperature on the rate of reaction.
…………………………………………………………………………………………………………….
5. Name two variables which are constant in an experiment to study the effect of catalyst on the
rate of reaction.
(i) …………………………………………………… (ii) ………………………………………………..
6. Why is the total volume of carbon dioxide gas collected from the experiment between calcium
carbonate and dilute sulphuric acid less than theoretical value?
…………………………………………………………………………………………………………….
6
Collision theory
1. What is collision theory ?
A theory used to explain chemical reactions in terms of
(i) ………………………………………………………………………………………………………….
(ii) ………………………………………………………………………………………………………..
(iii) ………………………………………………………………………………………………………..
The collision theory states that :
(i) A chemical reaction occurs when the reactant particles ……………………….. each other.
(ii) Not all collision result in the formation of …………………………………
(iii) A collision is ……………………………. only when the reactant particles have enough
energy to overcome the ………………………………………………… of the reaction and
when they collide in the proper orientation.
2. What is activation energy ?
The …………………………………… energy the colliding reactant particles must have before
collision between them can result in chemical reaction.
3. What is energy profile diagram ?
A graph represents the energy change that occurs in a chemical reaction.
4. Draw an energy profile diagram and explain the activation energy, Ea.
7
Collision theory and the factors affecting the rate of reaction
A. Conceptualize the collision theory by filling the blanks in the following paragraph:
According to the kinetic theory of matter, particles of matter are in continuous motion
and constantly in _______________ with each other. During a reaction, the particles of the
reactants, whether ____________, ______________ or __________, (clue : three type of
particles) must collide with each other for bond _________________ and bond
______________ to occur. However, not all collisions will result in a reaction to form
the________________ (clue : substances formed when two or more reactants reacted). Only
those collisions, which achieved a minimum amount of energy, called _______________
energy, and with the correct orientation, will result in a reaction. These types of collisions are
called _____________ collisions. If the particles collide with energy less than the activation
energy needed for reaction or with the wrong _______________, they simply bounce apart
without reacting. These types of collisions are known as _____________collisions. The above
theory which relates the movement of particles, collision of particles, activation energy,
orientation of the colliding particles and effective collisions resulting in reactions is termed as
collision _______________.
B. Collision theory and factors affecting the rate of reactions.
(i) Effect of surface area
When the size of a fixed mass of solid reactant is smaller, the _____________________
exposed to collision with the particles of the other reactants is _____________. Thus, the
frequency of collision among the reacting particles at the surface of the solid reactant
____________ ___. This leads to an ___________________ in the frequency of effective
collision and hence, a _____________ rate of reactions.
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(ii) Effect of concentration and pressure
An increase in the concentration of the solution of a reactant or in the pressure of gaseous
reactants will result in an _____________________________ in the rate of reaction. Why?
When the concentration of the solution of a reactant increases, the _______________________
volume of the solution of this reactant also _______________. With more particles per unit
volume of the solution, the number of collisions per unit time between the reacting particles
__________________. Thus, the frequency of effective collision ________________ and
hence, the rate of reaction becomes ___________________.
(iii) Effect of temperature
An increase in temperature will increase the _________________ of the reacting particles. This
leads to the following two changes. Firstly, the particles move _________________ and collide
more often with one another. Thus, the frequency of collision is ________________
Secondly, more colliding particles have ____________ energy which are enough to overcome
the activation energy. Both these factors contribute to the _______________ ____ frequency of
effective collision and hence, a _____________ rate of reaction.
(iv) Effect of catalyst
The presence of a catalyst in a chemical reaction allows the reaction to take place through an
alternative path which requires a ______________ activation energy can be shown in the
energy profile diagram. Thus, __________ colliding particles are able to achieve the
_____________ activation energy. This means that the frequency of effective collision
__________________and hence, a _______________ rate of reaction.
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Section A : Structured Question
1 The table below shows the volume of hydrogen gas released when 50.00 cm3 of sulphuric acid
solution reacts with 5.0 g of granulated zinc.
Time/s
Volume of
hydrogen gas
released/cm3
(a)
0
30
0.00
80.00
60
90
125.00
165.00
120
190.00
150
210.00
180
210.00
210
210.00
Write the chemical equation for the reaction between zinc and sulphuric acid.
…………………………………………………………………………………………
[2 marks]
(b)
Calculate the overall average rate of reaction of this experiment.
(c)
(i) Draw the graph of the volume of hydrogen gas released against time.
[1 mark]
[4 marks]
(ii) From the graph , calculate the rate of reaction at the 80th seconds.
[2 marks]
(d)
Instead of measuring the volume of hydrogen gas released, state another
method that can be used to calculate the rate of reaction in this experiment.
………………………………………………………………………………………………..
[ 1 mark]
10
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2.
An experiment was carried out to investigate the effect of the size of the marble chips on
the rate of reaction. A burette was filled with water and inverted in a basin containing
water. The initial burette reading was recorded.
5.0 g of large marble chips were placed in a conical flask. 50 cm 3 of 0.1 mol dm-3
hydrochloric acid, HCl was added into a conical flask. The conical flask was closed with
a stopper fitted with a delivery tube directed to the burette and the stop-watch was
started simultaneously. The burette reading was recorded at 30-seconds intervals.
Experiment was repeated by using 5.0 g of small marble chips.
Diagrams below show the burette readings for the experiment between large marble
chips with hydrochloric acid.
(a)
Record the volume of carbon dioxide gas in the spaces provided
50
41
32
49
40
31
48
39
30
Burette reading
……… cm3 at 0 min
Burette reading
……… cm3 at ½ min
Burette reading
……… cm3 at 1 min
25
20
16
24
19
15
23
18
14
Burette reading
……… cm3 at 1½ min
Burette reading
……… cm3 at 2 min
12
Burette reading
……… cm3 at 2½ min
12
10
9
11
9
8
10
8
7
Burette reading
……… cm3 at 3 min
Burette reading
……… cm3 at 3½ min
9
9
8
8
7
7
Burette reading
……… cm3 at 4½ min
(b)
Burette reading
……… cm3 at 4 min
Burette reading
……… cm3 at 5 min
[3 marks]
Construct a table showing the changes of time, burette readings and volumes of
carbon dioxide gas liberated for the experiment.
[3 marks]
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(c)
Table 1 shows the volume of carbon dioxide gas liberated when the experiment
was repeated by using 5.0 g of small marble chips.
Time /min
Volume of
carbon
dioxide /
cm3
0
½
1
1½
2
2½
3
3½
4
0.00 20.00 29.00 35.00 38.00 40.00 41.50 41.50 41.50
TABLE 1
Based on the data in (b) and Table 1, draw the graphs volume of carbon dioxide
gas liberated against time for both experiments on the same axes on Page 17.
[3 marks]
(d)
State the relationship between the size of marble chips and the rate of reaction?
…………………………………………………………………………........
………………………………………………………………………………
………………………………………………………………………………
[3 marks]
(e)
Meat which is cut into small pieces takes a shorter time to cook compared to
meat that is cut into big pieces. Explain why?
………………………………………………………………………………
………………………………………………………………………………
………………………………………………………………………………
[3 marks]
14
15
(e)
Complete the table below based on the experiment.
Name of variables
(i) Manipulated variable
............................................................
Action to be taken
(i) The way to manipulate variable
........................................................
............................................................
.........................................................
............................................................
.........................................................
(ii) Responding variable
............................................................
(ii) What to observe in the
responding variable
............................................................
.........................................................
.............................................................
..........................................................
(iii) Fixed variable
.............................................................
(iii) The way to maintain the fixed
Variable
.............................................................
.........................................................
............................................................
.........................................................
[3 marks]
Section B : Essay Question
3 (a)
One of the factors that affect the rate of reaction is the size of particles.
Two kilograms of potatoes, cut into big pieces, takes a longer time to
cook compared to two kilograms of potatoes cut into small pieces.
Explain the above statement based on the size of the particles.
[2 marks]
(b)
A student carried out an experiment to investigate the effect of concentration on the rate
of reaction.
The chemical equation for the reaction is,
Na2S2O3
+ H2SO4
Na2SO4 + H2O + S + SO2
16
Set-up of
apparatus
The table below shows the time taken for the mark ‘X’ to disappear from sight when
sulphuric acid was added to sodium thiosulphate solution in a conical flask.
Experiment
Volume of 1.0 mol
dm-3 sulphuric acid
Concentration of
sodium thiosulphate
solution/ mol dm-3
Time taken for mark
‘X’ disappears from
sight / s
(i)
(ii)
(iii)
(iv)
(v)
(vi)
I
5.0
II
5.0
III
5.0
IV
5.0
0.18
0.16
0.08
0.04
18.2
20.0
40.8
83.2
Write an ionic equation for this reaction.
[3 marks]
Based on the result of the experiment, plot a graph of the concentration of sodium
thiosulphate solution against time.
[4 marks]
Using the graph in b(ii), determine the time taken for mark ‘X’ disappears from
sight if 0.12 mol dm-3 of sodium thiosulphate solution is used in this experiment.
[2 marks]
Rate of reaction is directly proportional to 1/time.
Sketch a graph for the concentration of sodium thiosulphate solution against
1/time.
[2 marks]
By using collision theory, explain why there are differences in the rate of reaction
between Experiment I and Experiment IV .
[5 marks]
50.0 cm3 of 0.5 mol dm-3 of sodium thiosulphate solution reacts with excess
sulphuric acid. Calculate the mass of sulphur produced.
[Relative atomic mass : S, 32]
[4 marks]
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