cxc rates.pdf

1
MINISTRY OF EDUCATION
SECONDARY ENGAGEMENT PROGRAMME
CHEMISTRY
GRADE 10
TERM 3
Topics per lesson
WEEK
#
LESSON
1 2 3
1 Rates of reaction Factors affecting rate
of reaction –
Concentration of
reactants
Factors affecting rate
of reaction –
Temperature
2 Factors affecting rate
of reaction – Surface
area
Factors affecting rate
of reaction –
Presence of catalyst
Rates of reaction –
Summary
3 Graphical interpretation of data obtained in studying rates of reaction
4 Exothermic and
Endothermic
reactions
Enthalpy of reaction Heat of solution
5 Heat of neutralisation Heat of combustion Review of Energetics

2
CHEMISTRY
GRADE 10
WEEK 1 LESSON 1
TOPIC: Rates of Reaction
Chemical reactions occur at greatly varying speeds. In the laboratory, we are generally
accustomed to reactions occurring at moderate speeds. However, natural processes involving
chemical reactions may occur at different speeds. Some may be so slow that they take millions of
years and some very fast that they occur within a fraction of a second.
The table below gives the reaction time for some chemical reactions.
Reaction Reaction time
Reaction between sliver nitrate solution and sodium chloride solution Fraction of a second
Oxidation of calcium metal Minutes
Burning of coal in fire Hours
Rusting of iron Weeks
Weathering of stonework in buildings Hundreds of years
Radioactive decay of uranium – 238 Millions of years

3
The rate of a chemical reaction can be generally defined as the measured change in a given
property per unit time for the change to take place.
Rate of reaction =
The property changes which can be measured more easily include:
Volume of a gaseous product
Colour intensity
Amount of a precipitate formed.
Decrease in mass (if a gas is evolved)
Conditions necessary for chemical reactions to take place (Collision Theory)
1. There must be collision between the reactant particles. Not all collisions will produce a
reaction. Chemists have discovered that only a small fraction of the reactant particles will
produce a reaction.
2. Reactant particles must have sufficient energy to break the bonds of the reactants and
form the bonds of the products. A reaction will only occur if this energy barrier is
overcome. The combined minimum energy which the reactant particles must have in
order to react is called the activation energy of the reaction.
3. Reactant particles must collide with the correct orientation. Even high energy collisions
with sufficient activation energy will not react when they collide if they are not properly
oriented.

4
CHEMISTRY
GRADE 10
WEEK 1 LESSON 1 Worksheet
1 Define the term rate of reaction
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2 Briefly explain what the conditions necessary for a chemical reaction to take place.
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3 State four (4) factors that affect the rate of a chemical reaction.
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5
CHEMISTRY
GRADE 10
WEEK 1 LESSON 2
TOPIC: Factors affecting the rate of a chemical reaction – Concentration of reactants
An increase in the concentration of a reactant in a solution will result in more particles being
crowded in the same space and hence the likelihood that they will have more frequent collisions
with each other.
An increase in concentration of the reactants increases the rate of a reaction.
Experiment to investigate the effect of concentration on reaction rate (The disappearing cross)
When acid is added to sodium thiosulphate solution, a fine colloidal suspension of Sulphur is
formed. This suspension scatters light. Viewed through the suspension, a cross on a sheet of
paper disappears when enough Sulphur particles are formed.
Procedure:
1.Using a measuring cylinder, place 50 cm3
of 0.1 mol dm-3
sodium thiosulphate into a conical
flask.
Lower concentration Higher concentration

6
2.Add 50 cm3
of 0.5 mol dm-3
sulphuric or hydrochloric acid to this solution, noting the time that
you do so.
3.Place the conical flask over the cross and record the time it takes for the cross to be no longer
visible when viewed from above. Discard the mixture and wash the conical flask.
4.Repeat step 3, using instead the next thiosulphate/water mixture shown in the table below
Experiment
#
Volume of
acid /cm3
Volume of
thiosulphate /cm3
Volume of
water /cm3
Time, t/
s
/ s-1
1 50 50 0
2 50 45 5
3 50 40 10
4 50 35 15
5 50 30 20
6 50 25 25
7 50 20 30
Plot a graph of against volume of sodium thiosulphate used.
Equation for such a reaction above is as follows:
Na2S2O3 (aq)+ 2HCl (aq) 2 NaCl(aq) + S (s) +SO2(g) + H2O (l)

7
CHEMISTRY
GRADE 10
1 State the effect of concentration on the rate of a chemical reaction:
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2 The table below gives results from an experiment previously described.
Experiment
#
Volume of
acid /cm3
Volume of
thiosulphate /cm3
Volume of
water /cm3
Time, t/
s
/ s-1
1 50 50 0 33.24
2 50 45 5 38.57
3 50 40 10 46.31
4 50 35 15 53.52
5 50 30 20 64.22
6 50 25 25 76.39
7 50 20 30 107.43
(a) Complete the table above.
(b) Plot a graph of against volume of sodium thiosulphate used, on the graph paper
provided.
(c) Comment on the shape of the graph in relation to the effect of concentration of reactants
to the rate of the reaction.

9
CHEMISTRY
GRADE 10
WEEK 1 LESSON 3
TOPIC: Factors affecting the rate of a chemical reaction – Temperature
When the temperature of a reaction mixture is raised, more heat is supplied to the reactant
particles resulting in greater internal energy and faster movement of particles. The increase has
two effects:
1. More particles will have energy equal to or greater than the activation energy.
2. The particles will collide more frequently due to an increase in the kinetic energy. This
will result in an increase in more successful (effective)collisions and hence an increase in
the rate of reaction.
An increase in the temperature increases the rate of a chemical reaction.
Examples of the effect of temperature on the rate of reaction are
1. The refrigerator has a low temperature to reduce the chemical reactions which cause the
spoilage of food.
2. Food cooks faster in a pressure cooker because the water is boiling at 120 0
C instead of
100 0
C.

10
There are several experiments that can be carried out to investigate the effect of temperature on
the rate of a reaction.
A modification of the experiment stated in the first lesson is one of these experiments.
Procedure:
1. Draw a cross on a piece of white paper.
2. Place the conical flask over the cross.
3. Add 50 cm3
sodium thiosulphate solution and measure the temperature.
4. Add 5 cm3
dilute hydrochloric acid to start the reaction and start the timing.
5. Stop the clock when you can no longer see the pencil mark.
6. Repeat at least five times at a range of temperatures by warming the thiosulphate before
adding the acid.
7. Draw a line graph of temperate against the reciprocal of time, .

11
CHEMISTRY
GRADE 10
One can usually follow the rate of a reaction by monitoring the rate of disappearance of the
reactant or appearance of the product. When aqueous sodium thiosulphate (Na2S2O3) reacts with
hydrochloric acid, a precipitate of sulphur, sulphur dioxide, sodium chloride and water are
formed as the only products. The rate of this reaction can be followed by measuring the time
taken for a certain amount of sulphur precipitate to be formed.
A student investigates the effect of temperature on the rate of this reaction. The figure below
shows the stopwatch times taken for a fixed amount of sulphur precipitate to appear and the
corresponding thermometer readings. The concentration of all the reactants are kept constant in
these experiments.

12
(a) In the space below, construct a suitable table and record on it, the temperatures at which
the reaction took place with the corresponding times in seconds for the formation of
sulphur.
(b) Using the graph provided, plot a graph of temperature versus time in seconds.
(c) What conclusion can be drawn about the rate of the reaction from the graph?
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(d) From the information given in the introduction, write a balanced chemical equation for
the reaction between aqueous sodium thiosulphate and hydrochloric acid.
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13
CHEMISTRY
GRADE 10
WEEK 2 LESSON 1
TOPIC: Factors affecting the rate of a chemical reaction – Surface area
In reactions involving solids, reactions can only take place when the surface of the solid comes
in contact with other reacting particles. In order to have more collisions and reactions between
the particles, the surface area of the solid must be increased by subdividing the particle into
smaller pieces. Minutely divided particles have very large surface areas. Breaking the solid into
smaller pieces exposes more surfaces, resulting in more particles being available to react. For
reactions involving solids, liquids and gases dissolved in solution, the solution should be
thoroughly mixed to maximise the contact of the reacting species.
An increase in the surface area (i.e. the smaller the particle size) of the solid increases the rate of
the reaction.

14
One experiment that can be carried out to investigate the effect of particle size on the rate of
reaction is reacting magnesium powder, magnesium ribbon and magnesium turnings with
hydrochloric acid.
Procedure
1. Using a measuring cylinder, place 50 cm3
of the 0.5 mol dm-3
hydrochloric acid into a
conical flask which is connected to a gas syringe. Remove the stopper and introduce 0.09
g of magnesium powder into the conical flask and quickly replace the stopper. Record the
volume of gas in the syringe at suitable time intervals, e.g. 20 or 30 seconds intervals.
2. Repeat the above step using magnesium turnings and magnesium ribbon separately,
recording the volume of gas collected with time.
3. Plot a graph of the volume of gas produced against time on the same graph paper.

15
CHEMISTRY
GRADE 10
Sam conducted a series of experiments to investigate the effects of various factors on the rate of
the reaction between magnesium and 1 M iron (III) chloride solution. Two 5 cm strips of
magnesium were used.
One of the strips was further cut into five 1cm strips and placed into 100 cm3
of the iron (III)
chloride solution.
The other 5cm strips were placed into an equal volume of the iron (III) chloride solution.
The figure below shows the reactants that were used to investigate the effect of one factor on the
rate of reaction at the start and after 30 seconds.

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(a) Describe what will happen to the contents in Beaker A after 30 seconds.
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(b) How would the contents of Beaker B differ from that of Beaker A after each is left for
30 seconds?
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(c) Explain your answer in (b) above.
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17
CHEMISTRY
GRADE 10
WEEK 2 LESSON 2
TOPIC: Factors affecting the rate of a chemical reaction – Presence of a catalyst
In many chemical reactions the addition of certain substances (which are not reactants) are often
used to change the rate of a chemical reaction. These substances are called catalysts.
A catalyst is a substance which will alter the rate of a chemical reaction, but remains unchanged
chemically at the end of the reaction. Positive catalysts will lower the activation energy, hence
many more reactant particles will attain the activation energy and are able to react when they
collide. In the case of negative catalyst, the activation energy is raised and decreases the rate of a
reaction.
Examples of reactions affected by catalysts:
1. Hydrogen peroxide will decompose rapidly to form oxygen and water if magnesium (IV)
oxide is added as catalyst.
2. In the synthesis of ammonia from nitrogen and hydrogen, iron is used as a catalyst to
increase the rate of reaction.
3. Reaction between hydrogen and chlorine is negligible in the absence of light but
explosive in sunlight (photocatalyst)
4. Photosynthesis in plants (photocatalyst)
5. Salivary amylase breaking down starch into maltose (enzyme)
The use of manganese (IV) oxide in the decomposition of hydrogen peroxide to oxygen and
water is a common experiment to investigate the effect the catalyst on the rate of a chemical
reaction.

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Procedure:
1. To 50 cm3
of hydrogen peroxide, add 45.0 cm3
of water, 1 drop of sodium hydroxide
solution and 0.05 g of powered manganese (IV) oxide.
2. Using the apparatus above, collect the oxygen gas given off, noting the volumes at half –
minute intervals for 4 minutes.
3. Repeat steps 1 and 2, using firstly 0.10 g of powdered manganese (IV) oxide, then 0.20 g
of powered manganese (IV) oxide.
4. On the same graph paper, plot volume of oxygen against time for all four experiments.

19
CHEMISTRY
GRADE 10
Steve knows that hydrogen peroxide decomposes to produce oxygen and water, and that catalysts
can be used to speed up this reaction.
Steve conducted a series of experiments to investigate the effect of mass of catalyst on the rate of
decomposition of hydrogen peroxide. For each experiment, he combined a different mass of the
catalyst, manganese dioxide (MnO2), with 50 cm3
of 0.8 mol dm-3
hydrogen peroxide solution
and measured the volume of oxygen produced. He then calculated the rate of the reaction for
each quantity of catalyst used and recorded in the information in the table below.
Mass of manganese dioxide (g) Rate of reaction (10-3 g O2 s-1)
0.7 0.6
1.0 1.3
2.0 2.5
3.0 3.8
4.0 5.0
(a) Write a balanced chemical reaction to show the decomposition of hydrogen peroxide.
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(b) On the graph paper provide, plot a graph showing rate of reaction versus mass of
manganese dioxide.

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(c) From the graph, describe the relationship between rate of reaction and the mass of the
catalyst.
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(d) Explain how the catalyst affects the rate of reaction as described in (c) above.
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22
CHEMISTRY
GRADE 10
WEEK 2 LESSON 3
TOPIC: Factors affecting the rate of a chemical reaction – Summary
The rate of a reaction is usually fastest when it begins. This is because the concentration of the
reactants is the greatest. Hence, the molecules will collide frequently thus causing a fast reaction.
The rate gradually decreases as the reactants are used up and their concentration decreases. The
reaction will stop when one, or both of the reactions is/are used up.
If a solid is reacting with a solution, its surface area will decrease gradually and there will be less
contact between the reacting particles. This decreasing surface area will slow down the reaction.
If on the other hand, heat is evolved during the reaction, the molecules will speed up and collide
more frequently and more effectively. This may cause the reaction to start slowly and then speed
up. This speeding up can also be explained by one of the reactants initially having a surface
coating which dissolves, enabling the other reactant to react with it more effectively.
Catalysts cannot make more products in the long run, as this is governed by the quantities of
reactants, but they can make the same reaction proceed at a quicker or slower rate by lowering
the activation energy for faster reaction and raising it for a slower reaction.

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Factor Effect on reaction rate Mechanism by which factor affects
reaction rate
Concentration of
reactants
If the concentration increases,
the rate increases
Increasing the concentration increases
the number of particles per unit
volume. Therefore, the frequency of
collisions increases
Temperature If the temperature increases,
the rate increases
Increasing the temperature increases
the kinetic energy of particles, causing
them to move faster and :
collide more frequently;
collide with more energy so that more
collisions produce sufficient energy to
break bonds in the reactants
Particle size Decreasing the particle size
(breaking the solid into
smaller pieces) causes an
increase in the rate
Reaction occurs at the surface of a
solid. Breaking the solid (decreasing
the particle size) increases the surface
area exposed. Therefore, more area for
collision is available.
Catalyst Adding a catalyst increases
the rate
(A negative catalyst or
inhibitor decreases the rate)
Catalysts may provide an alternative
pathway for a reaction that has a lower
activation energy.
A solid catalyst may catalyse reactions
in gaseous state or aqueous solutions
by providing a surface for reactants to
react.

24
CHEMISTRY
GRADE 10
(a) Define the term ‘rate of reaction’
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(b) State 3 factors that will affect the rate of a chemical reaction.
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(c) Discuss how each of the factors stated in (b) affect the rate of a chemical reaction.
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(d) Using a labelled diagram, describe an experiment that can be used to investigate how one
of the factors you stated in part (b) affect the rate of a reaction.
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26
CHEMISTRY
GRADE 10
WEEK 3 LESSON 1
TOPIC: Graphical interpretation of data obtained in studying rates of reaction
Sally performed an experiment which consisted of a series of six tests to investigate the effect of
temperature on the rate of reaction. The same mass of calcium carbonate, CaCO3, chips was
allowed to react with an excess of dilute hydrochloric acid at different temperatures. Carbon
dioxide gas was produced from the reaction and the time taken to collect 50 cm3
of this gas for
EACH test is shown below.
The six tests were carried out at different temperatures using 1.0 g CaCO3 chips and 100 cm3
of
1.0 mol dm-3
hydrochloric acid.

27
(a) From the stopwatches displayed, record the times taken for the carbon dioxide gas to be
collected in the appropriate spaces in the following table. The time taken for Test 1 has
already been recorded.
Test Temperature (oC) Time taken (s) Reciprocal Time (s-1)
1 18 51.5 0.019
2 23
3 28
4 32
5 37
6 43
(b) Calculate the reciprocal times ( ) and record them to 3 decimal places in the
appropriate spaces in the table above. The reciprocal time for Test 1 has already been
calculated.
(c) Using the axes provided, plot a graph of reciprocal time versus temperature for
Tests 1 – 6. Draw the best curve through the points.

29
CHEMISTRY
GRADE 10
WEEK 3 LESSON 2
Hydrogen peroxide (H2O2) decomposes to produce oxygen and water. The rate of reaction can be
increased by the use of catalysts. The effect of the mass of a catalyst on the rate of
decomposition of hydrogen peroxide was investigated.
For EACH experiment, a different mass of the catalyst, manganese (IV) oxide (MnO2) was
combined with 50 cm3
of 0.8 mol dm-3
hydrogen peroxide solution and the volume of oxygen
produced was measured. The masses are shown on the balances displayed below.

30
The rate of reaction for EACH quantity of catalyst used was calculated and recorded in the table
below. Use the balances shown above and complete the table.
RATE OF REACTION BY MASS OF MANGANESE (IV) OXIDE
Experiment Mass of manganese (IV) oxide (g) Rate of reaction (mLs-1)
1 0.0 0.0
2 0.6
3 1.8
4 2.7
5 4.5
6 5.0
(a) Using the axes given the graph paper provided, plot a graph of rate of reaction verses
mass of manganese (IV) oxide using the information in the table above. One point has
already been plotted

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(b) Using your graph,
(i) describe the relationship between the rate of reaction and the mass of the catalyst
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(ii) determine the rate of reaction using 3.0 g of the catalyst
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(iii) determine the volume of oxygen produced after 10 s using the value obtained from (b)
(ii) above
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33
CHEMISTRY
GRADE 10
WEEK 3 LESSON 3
Carol carried out a number of experiments to investigate the effect of concentration on the rate of
reaction. Different concentrations of aqueous potassium iodate (KIO3) were allowed to react with
a fixed concentration of aqueous sodium hydrogen sulphite (NaHSO3) in the presence of
sulphuric acid and starch as indicated in the table below. The time taken for a blue – black colour
to appear was noted.
Experiment Solution 1
(cm3)
Solution 2
(cm3)
Distilled
water
(cm3)
Time taken
for blue –
black
colour to
appear (s)
Reciprocal
time (s-1)
Concentration of
KIO3 after mixing
(mol dm-3)
1 5 10 35 83.5 0.012 0.0010
2 10 10 30 0.0020
3 15 10 25 0.0030
4 20 10 20 0.0040
5 25 10 15 0.0050
6 20
Solution X
10 20

34
(a) From the stop watches displayed below, record the times taken for the blue – black colour
to appear in the appropriate spaces in the table. The time taken for Experiment 1 has
already been recorded for you.
(b) Calculate the reciprocal times and record them to 3 decimal places in the appropriate
spaces in the table. One of the times has already been recorded for you.
(c) Using the axes in the graph paper provided, plot a graph of concentration of KIO verses
the reciprocal time for Experiments 1 to 5. Draw the best straight line through the points.

35
(d) Based on the graph, what deduction can be made about the effect of concentration of
aqueous KIO3 on the rate of reaction?
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(e) Experiment was carried out using Solution X, which contained an unknown concentration
of KIO3. Using the reciprocal time calculated in Experiment 6, determine from your
graph, the concentration of KIO3 in this reaction mixture.
(f)(i) State the responding variable in this experiment
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(ii) State the controlled variable in the experiment
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37
CHEMISTRY
GRADE 10
WEEK 4 LESSON 1
Topic: ENERGETICS – Exothermic and Endothermic reactions
During a chemical reaction:
Bonds are broken in the reactants – energy is absorbed
New bonds are formed in the products – energy is released
Reactants  Products
Bonds broken
Energy absorbed
Bonds formed
Energy released
An exothermic reaction is a change in which heat energy is given out to the environment. The
reaction becomes hotter as this energy is released, e.g. neutralisation reactions, dissolving
ethanol in water, burning ethanol and other fuels.
For an exothermic reaction,
Energy absorbed in breaking old bonds < Energy released in forming new bonds
An endothermic reaction is a change in which heat energy is absorbed from the environment.
The reaction becomes cooler as this energy is absorbed, e.g. thermal decomposition of
carbonates, dissolving ammonium chloride or potassium nitrate in water.
For an endothermic reaction,
Energy absorbed in breaking old bonds > Energy released in forming new bonds

38
CHEMISTRY
GRADE 10
1 In terms of bond breaking and bond formation, differentiate between endothermic and
exothermic reactions
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2 Draw energy profile diagrams for exothermic and endothermic reactions

39
CHEMISTRY
GRADE 10
WEEK 4 LESSON 2
Topic: ENERGETICS – Enthalpy change of a reaction
An enthalpy change is the heat energy exchanged between a chemical reaction and its
surroundings at constant pressure. The symbol for enthalpy change is ΔH. The unit for enthalpy
change is kJ mol-1
.
Enthalpy change of a reaction = Energy content of products – Energy contents of reactants
ΔHreaction = Hproducts – Hreactants
During an endothermic reaction, heat energy is absorbed. That is, the products have more
energy than the reactants (Hproducts > Hreactants).
ΔH is positive (ΔH +ve) for an endothermic reaction.
During an exothermic reaction, heat energy is released to the surroundings. That is the energy
content of the products is less than the energy content of the reactants (Hproducts < Hreactants).
ΔH is negative (ΔH –ve) for an exothermic reaction.

40
An energy profile diagram is one showing energy of reactants and/or products during the course
of a reaction. The figures below show the energy profile diagram for an exothermic reaction and
endothermic reaction respectively.
Exothermic reaction Endothermic reaction
Activation energy is the energy barrier of a reaction. It is the energy that reactants must be
given, in excess of the energy they normally possess, in order to start forming products.
The figures below show the energy profile diagram for an exothermic reaction and endothermic
reaction showing the activation energy.

41
A catalyst is a substance that increases the rate of a reaction. It works by lowering the activation
energy. A catalyst provides an alternative pathway for the reaction which requires less activation
energy than the normal pathway. As a result, more reactant particles have the required energy to
react when they collide, and the reaction speeds up because there are more effect collisions in the
same length of time.
The figures below show the energy profile diagrams with and without the use of a catalyst for
exothermic and endothermic reactions.

42
CHEMISTRY
GRADE 10
1 Define the term enthalpy change
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2 Write the formula for enthalpy change
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3 Compare exothermic and endothermic reactions in terms of enthalpy change
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43
4 With the aid of a labelled energy profile diagram, explain how a catalyst works in a
chemical reaction.

44
CHEMISTRY
GRADE 10
WEEK 4 LESSON 3
Topic: ENERGETICS – Heat of solution
Heat of solution is the amount of heat evolved or absorbed when 1 mole of solute is completely
dissolved in water (so that further dilution produces no further heat change).
When alkali metal hydroxides dissolve in water, the reaction is always exothermic. The value of
ΔH is negative. The temperature of the solution increases and we have to measure the highest
temperature reached.
When salts dissolve in water, the energy change can be exothermic or endothermic depending of
the salt. When potassium nitrate or ammonium nitrate dissolves in water, heat is absorbed. The
value of ΔH is positive (endothermic). The temperature of the solution decreases and we have to
measure the lowest temperature rather than the highest.
Procedure for experiment to determine the heat of solution
1. Place a known volume of water in a polystyrene cup.
2. Record the temperature of the water.
3. Add a known mass of the solid to the water.
4. Stir the reaction mixture and record the highest/lowest temperature

45
Sample question
A 2.58 g sample of potassium nitrate was added to 100 cm3
of water in a Styrofoam cup. The
initial temperature of the water was 22.5 0
C and the temperature after mixing was 20.4 0
C.
Calculate the heat of solution of potassium nitrate.
[Assume specific heat capacity of the solution is 4.2 J g-1 0
C; Density of water = 1 gcm-3
]
Use the formula EH = mcΔT m= mass of solution
ΔT= temperature change
c = Specific heat capacity
Solution
Mass of water = 100 g
Mass of solution = 100 g + 2.58 g = 102.58 g
Change in temperature, ΔH = 2.1 0
C
EH = mcΔT
EH = 102.58 g x 4.2 J g-1 0
C x 2.1 0
C
EH = 904.7556 J
Mass of 1 mol of KNO3 = 39 + 14 + (16 x 3) g = 101 g
Number of moles of KNO3 =
.
= 0.0256
Heat of solution of 0.0256 mol of KNO3 = 904.7556 J
Heat of solution of 1 mol of KNO3 =
.
.
= 35342 J mol-1
= 35.3 kJ mol-1
Since the reaction is endothermic, ΔH = + 35.3 kJ mol-1

46
CHEMISTRY
GRADE 10
1 When 1.225 g of potassium chlorate, KClO3 was added to 150.0 g of water in a
calorimeter, the temperature dropped by 0.65 0
C. The heat capacity of water is 4.2 J g-1 0
C-1
.
Assume the specific heat capacity of the solution equals that of pure water and the calorimeter
neither absorbs nor leaks heat. What is the heat of solution of solid potassium chlorate?
2 In a certain experiment, 50.0 g of sodium hydroxide was completely dissolved in
200 cm3
of 28.0°C water in a Styrofoam cup. The final temperature was measured at 47.0 0
C.
Assuming no heat loss, calculate the heat of solution of sodium hydroxide.
[Assume specific heat capacity of the solution is 4.2 J g-1 0
]

47
CHEMISTRY
GRADE 10
WEEK 5 LESSON 1
Topic: ENERGETICS – Heat of neutralisation
Heat of neutralisation is the heat evolved when one mole of hydrogen ions, H+
, from an acid
reacts with one mole of hydroxyl ion, OH-
from an alkali to form one mole of water.
The heat of neutralisation for any strong acid and any strong alkali is about – 57 kJ mol-1
, since
the energy change is for the common reaction:
OH-
(aq) + H+
(aq)  H2O (l) ΔH = – 57 kJ mol-1
Procedure for experiment to determine the heat of neutralisation of sodium hydroxide by
hydrochloric acid.
1. Place a known volume of 1.0 mol dm-3
aqueous sodium hydroxide in a polystyrene cup
(calorimeter).
2. Record the temperature of the aqueous sodium hydroxide.
3. Add the same volume of 1.0 mol dm-3
hydrochloric acid to the cup. The acid should be at
the same starting temperature as the sodium hydroxide.
4. Stir the reaction mixture and record the highest temperature reached.

48
Worked example
When 25 cm3
of hydrochloric acid of concentration 1.0 mol dm-3
is added to 25 cm-3
of
potassium hydroxide of concentration 1.0 mol dm-3
, the temperature rises from 21.1 0
C to 27.3
0
C. Calculate the heat of neutralistion for this reaction.
Number of moles of KOH = concentration x volume
= 1.0 mol dm-3
x dm3
[Convert cm3 to dm3 since concentration is expressed as mol dm-3]
= 0.025 mol
Number of moles of HCl = concentration x volume
= 1.0 mol dm-3
x dm3
= 0.025 mol
Equation: KOH (aq) + HCl (aq)  KCl (aq) + H2O (l)
According to equation, 1 mol of KOH reacts with 1 mol of HCl to form 1 mol H2O
Therefore, 0.025 mol of KOH will react with 0.025 HCl to form 0.025 mol of H2O

49
EH = mcΔT
Final volume of solution = 25 cm3
+ 25 cm3
= 50 cm3
Mass of solution = 50 g [Density of solution = 1 gcm-3
]
ΔT = (27.3 – 21.1) 0
C = 6.2 0
C
EH = 50 g x 4.2 J g-1 0
C x 6.2 0
C
EH = 1302 J
Heat evolved in forming 0.025 mol of H2O = 1302 J
Heat evolved in forming 1 mol of H2O =
.
Heat evolved in forming 1 mol of H2O = 52 080 J mol-1
= 52 kJ mol-1
Since the reaction is exothermic, ΔH = – 52 kJ mol-1

50
CHEMISTRY
GRADE 10
25.0 cm3
of 2.0 mol dm-3
sodium hydroxide and 50.0 cm3
of 1.0 mol dm-3
hydrochloric acid both
at 30.0 0
C, are mixed together in a Styrofoam cup. On mixing, the temperature rises to 38.9 0
C.
Calculate the heat of neutralisation for the reaction in kJ mol-1
Use the following formula in your calculation:
Heat evolved = mass (g) x specific heat capacity (J g-1 0
C-1
) x change in temperature
c = 4.2 J g-1 0
C -1
Density of solution = 1 g cm-3

51
CHEMISTRY
GRADE 10
WEEK 5 LESSON 2
Topic: ENERGETICS – Heat of combustion
Heat of combustion is the heat change which occurs when one mole of a substance in its normal
state is completely burned in oxygen.
Heat of combustion can be found by burning a fixed mass of the substance and allowing the heat
produced to be transferred to a fixed mass of water.
If a small (homemade) spirit burner and a balance are available, the experiment can be completed
in a few minutes, and actual values can be used in the calculations. The calculation is best
explained by an example.

52
Worked example
A student used the apparatus below to find the value of heat of combustion of ethanol.
He obtained the following results:
Initial mass of spirit lamp and ethanol = 65.20 g
Final mass of spirit lamp and ethanol = 64.28 g
Final temperature of water in can = 47.1 0
C
Initial temperature of water in can = 28.5 0
C
Mass of water = 0.30 kg
Calculations:
Mass of ethanol burned = 65.20 g – 64.28 g = 0.92 g
Mass of 1 mole of ethanol (C2H5OH) = (12 x 2 + 1 x 5 + 16 + 1) g = 46 g
Number of moles of ethanol in 0.92 g =
.
mole = 0.02 mole
0.02 mole of ethanol is burned

53
m = 0.30 kg
c = 4200 J kg-1 0
C-1
ΔT = (47.1 – 28.5) 0
C = 18.6 0
C
Heat of combustion of 0.02 mole of ethanol = mcΔT
= 0.3 kg x 4200 J kg-1 0
C-1
x 18.6 0
C
= 23 436 J
Heat of combustion of 1 mole of ethanol =
.
= 1 171 800 J mol-1
= 1 171.8 kJ mol-1

54
CHEMISTRY
GRADE 10
Calculate the heat of combustion of ethanol using the following experimental data:
Initial mass of spirit lamp and ethanol = 52.50 g
Final mass of spirit lamp and ethanol = 52.04 g
Final temperature of water in can = 57.5 0
C
Initial temperature of water in can = 28.0 0
C
Volume of water = 100 cm3
[Given: Specific heat capacity of water = 4.2 J g-1 0
]

55
CHEMISTRY
GRADE 10
WEEK 5 LESSON 3
Topic: ENERGETICS – Review
A student carried out an experiment in order to determine the heat of combustion of candle wax
(a mixture of solid hydrocarbons) by using the apparatus shown below.
Procedure:
1. The conical flask was first weighed empty, then a known volume of water was added and
it was reweighed.
2. The conical flask was then clamped and encased by a can as shown above.
3. The initial temperature of the water in the flask was recorded.
4. The candle and the watch – glass were weighed and placed directly under the calorimeter
(the conical flask enclosed by the can).
5. The candle was lit and the heat generated was used to heat the contents of the
calorimeter.

56
6. After 15 minutes, the candle was extinguished and the HIGHEST temperature of the
water was recorded.
7. The candle and watch – glass were allowed to cool and then reweighed.
The results of the masses of the candle and water used, and the observed temperatures of the
water are shown below.

57
(a) Use the readings shown to complete the table below.
Mass of conical flask and water (g)
Mass of conical flask (g)
Mass of water (g)
Final temperature of water (0
C)
Initial temperature of water (0
C)
Temperature change (0
C)
Initial mass of candle and watch – glass (g)
Final mass of candle and watch – glass (g)
Mass of candle burnt (g)
(b)(i) Assuming that the heat absorbed by the conical flask
= (mass of the conical flask) x (0.861 J g-1 0
C-1
) x (temperature change),
calculate the heat absorbed by the conical flask used in the experiment.
(ii) Assuming that the heat absorbed by the water
= (mass of water in the conical flask) x (4.2 J g-1 0
C-1
) x (temperature change),
calculate the heat absorbed by the water in the conical flask.

58
(iii) Calculate the TOTAL heat absorbed by the calorimeter
Total heat absorbed by the calorimeter =
(heat absorbed by the conical flask) + (heat absorbed by the water in the conical flask)
(iv) Calculate the heat of combustion of the candle wax
Heat of combustion =
( )
( )
(c) What was the role of the can in this experiment?
______________________________________________________________________________

1
CHEMISTRY
GRADE 10
TERM 3
Topics per lesson
WEEK
#
LESSON
1 2 3
6 Problem solving of
Past CSEC Chemistry Paper 2
on topics completed in Grade 10
7
8
9
10

2
CHEMISTRY
GRADE 10
WEEK 6 LESSON 1
Topic: Effect of temperature on solubility of solids in water – Review
Recap:
A saturated solution contains as much solute as can be dissolved at a given temperature, in the
presence of undissolved solute.
Solubility is the mass of solute which will saturate 100 g of solvent at a given temperature.
Generally, the solubility of a solid increases as temperature increases.
A solution is a homogenous (same throughout) mixture of two or more substances, one of which
is usually a liquid.
A suspension consists of a substance, usually a liquid, which contains minute, but visible
particles held floating in the substance. If left undisturbed, the particles eventually settle.
A colloid consists of a substance, usually a liquid, which contains macromolecules or aggregates
of macromolecules held floating in the substance. The particles cannot be seen even with a
microscope. If left undisturbed, the particles do not settle.

3
Problem:
The solubility of a solid, X, in water at various temperatures is determined by the procedure
outlined below. This procedure comprises a series of experiment numbered 1 to 5. Some of the
data are recorded in the table that follows the procedure.
Procedure:
1. In Experiment 1, 2g of X is added to 4 cm3
of water in a boiling tube.
2. The tube is heated while stirring in a water bath until all of X has been dissolved.
3. The solution is then allowed to cool and the temperature at which the crystal of X first
appear is noted and recorded in the table.
4. In each of Experiments 2 to 5, the same mass of X (2 g) is added to a different volume of
water as indicated in the table.
5. In each case, the temperature at which the crystals first reappear is displayed on the
relevant thermometer as shown below.

4
(a) Complete the table below by
(i) recording the temperatures at which the crystals of X reappear in EACH experiment.
(ii) determining and recording the corresponding values for the solubility of X.
[At each temperature, Solubility of X = x 100; assume 1 cm3
of water = 1 g]
Experiment
Number
Mass of X (g) Volume of
water (cm3)
Temperature at
which crystals
reappear (0C)
Solubility of X
(g/100 g of
water)
1 2 4 91 50
2 2 8 57
3 2 12
4 2 16
5 2 20
(b) Using the axes provided on the graph paper,
plot a graph of solubility of X (g/100 g water) against temperature in 0
C. Draw a best – fit
curve through the points plotted.
(c) What deduction about the solubility of X can be made from the graph drawn in part (b)
above?
______________________________________________________________________________
(d) Using he equation given in part (a) and the graph drawn, calculate the minimum volume
of water which is required to dissolve 2 g of X at 60 0
C.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________

6
(e) Distinguish between ‘a solution’ and ‘a suspension’.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(f) Besides temperature, state TWO other factors that affect the rate at which a solute
dissolves.
______________________________________________________________________________
______________________________________________________________________________

7
CHEMISTRY
GRADE 10
WEEK 6 LESSON 2
Topic: Review of Atomic Structure, Structure and Bonding, Oxidation – Reduction
Reactions
Problem:
Different halogens can combine to form compounds. One such compound is ICl.
(a)(i) In the space below, draw a diagram to show the arrangement of electrons in the chlorine
atom. [Atomic number = 17]
(ii) Using valence shells only, draw a diagram to show the bonding which occurs in ICl.

8
(b) State TWO reasons why ICl is expected to have a low melting point.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(c) Analysis of a sample of ICl shows that it consists of molecules of the same molecular
formula, but different molar masses. What is a possible explanation for this?
______________________________________________________________________________
______________________________________________________________________________
(d) Write a balanced equation for the reaction which occurs when chlorine is reacted with
aqueous potassium iodide.
______________________________________________________________________________
(e) Based on the balanced equation you have written in (d) above, determine
(i) the change in oxidation number that the iodide ions undergo
______________________________________________________________________________
______________________________________________________________________________
(ii) whether chlorine is acting as an oxidising or a reducing agent. State a reason for your
answer.
______________________________________________________________________________
______________________________________________________________________________

9
CHEMISTRY
GRADE 10
WEEK 6 LESSON 3
Topic: Review of Electrolysis
Problem:
The applications of electrolysis can be varied. It can be used to extract some metals from their
compounds and to protect metals from corrosion.
(a)(i) Define the term ‘electrolysis’.
______________________________________________________________________________
______________________________________________________________________________
(ii) Describe what happens during the electrolysis of molten sodium chloride. Support your
answer with relevant balanced ionic equations.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________

10
(b) Aqueous sodium chloride can be electrolyzed using inert electrodes. Discuss the effect
the position of ions in the electrochemical series has on the products of this electrolysis.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(c) Aluminium is made corrosion resistant by anodizing it. Using a labelled diagram and
equations, explain what happens during anodizing of aluminium.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________

11
CHEMISTRY
GRADE 10
WEEK 7 LESSON 1
Topic: Review of States of Matter and Structure & Bonding
(a) Water exists in three states of matter while iodine exists in two.
(i) List the THREE states of matter in which water exists.
______________________________________________________________________________
(ii) Describe the strength of the forces of attraction present between the particles in EACH of
the three states you have mentioned in (a) (i) above.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________

12
(iii) When heated, iodine changes from one state into another. What is this process called?
______________________________________________________________________________
(iv) Describe how the energy of the iodine particles changes as iodine undergoes the process
mentioned in (a)(iii) above.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(b) Using appropriate diagrams, illustrate how the bonding in solid sodium chloride differs
from that of diamond.

13
(c) Describe TWO tests that are performed in the laboratory to distinguish between an ‘ionic
solid’ and a ‘molecular solid’. Suggest how the results of the tests described can be used
to distinguish between the two solids.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________

14
CHEMISTRY
GRADE 10
WEEK 7 LESSON 2
Topic: Review of Acids, Bases and Salts
Tums®
and Epsom salts are items commonly found in most household medicine cabinets.
Calcium carbonate is the main ingredient in Tums®
, an antacid used to relieve heartburn, acid
indigestion and upset stomach.
(a) What is an antacid?
______________________________________________________________________________
______________________________________________________________________________
(b) Describe ONE method for the preparation of dry calcium carbonate in the laboratory. In
your answer, include an equation for the reaction as well as the steps that are involved in
its preparation.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________

15
(c)(i) The main ingredient in Epsom salts is magnesium sulphate. List ONE use of Epsom salts
______________________________________________________________________________
(ii) In order to effectively use Epsom salts, it is usually made into a solution. Explain why
water molecules are able to dissolve Epsom salts.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________

16
CHEMISTRY
GRADE 10
WEEK 7 LESSON 3
(a) Electrolysis has a wide range of industrial applications. Electroplating is one such
application that is commonly used to make metals attractive.
(i) Define the term ‘electrolysis’
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(ii) Define the term ‘electroplating’
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(iii) List THREE other applications of electrolysis.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________

17
(b) Desiree wants to set up apparatus in the laboratory for the electrolysis of molten lead
bromide, PbBr2.
(i) Draw a fully labelled diagram of the apparatus she should use state the material from
which the electrodes are made.
Materials: _____________________________________________________________________
(ii) Write balanced equations to indicate the reactions which occurs at EACH electrode.
______________________________________________________________________________
______________________________________________________________________________

18
CHEMISTRY
GRADE 10
WEEK 8 LESSON 1
Topic: Review of Atomic Structure, Structure & Bonding
(a) Two isotopes of carbon are 𝐶 and 𝐶. Define the term ‘isotope’ and hence show by
calculation that 𝐶 and 𝐶 are isotopes.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(b) Radioisotopes are very useful in everyday life. For example, the Uranium – 235 isotope is
used in energy generation because it produces large amounts of energy when the atoms
split.
State THREE other uses of radioisotopes.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________

19
(c) Elements W and X react to form a compound. The electronic configuration of the
elements W and X are shown below:
W: 2,7 X: 2,8,2
(i) State the appropriate group and period to which EACH element, W and X, belongs.
Hence, indicate the type of bonding that occurs between W and X and write the formula
of the compound formed.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(ii) Suggest whether the resulting compound will dissolve in water. Explain your answer.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________

20
CHEMISTRY
GRADE 10
WEEK 8 LESSON 2
Topic: Review of Mole Concept and Electrolysis
(a) Lesley was asked to weigh 0.20 moles of aspirin to be used in a supervised experiment
during her chemistry laboratory class. Before doing so, she read the label, at the back of
the bottle, as shown below.
Aspirin
Drug
Aspirin is used an analgesic to relieve minor aches and pains, reduce fever, and as an
anti – inflammatory medication.
Formula: C9H8O4
Molar mass: 180 g mol-1
Melting point: 136 0
C
Boiling point: 140 0
C
Density: 1.40 g cm-3

21
(i) Define EACH of the following terms:
Mole:
______________________________________________________________________________
______________________________________________________________________________
Molar mass:
______________________________________________________________________________
______________________________________________________________________________
(ii) Calculate the mass Lesley would have to weigh to obtain 0.20 moles of aspirin.
______________________________________________________________________________
______________________________________________________________________________
(iii) Jared, another student in Lesley’s class, weighed 18.0 g of aspirin. Calculate the number
of moles of aspirin he weighed.
______________________________________________________________________________
______________________________________________________________________________

22
(b) Ethanoic acid is one of the products of the hydrolysis of aspirin.
Hydrolysis of aspirin
Calculate the mass of ethanoic acid formed when Jared’s 18.0 g of aspirin is hydrolysed.
[Molar mass of ethanoic acid: 60.0 g mol-1
]
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(c) Ethanoic acid is known to be an electrolyte.
(i) Define the term ‘electrolyte’
______________________________________________________________________________
______________________________________________________________________________
(ii) Identify the ions that are produced from ethanoic acid during electrolysis
______________________________________________________________________________
______________________________________________________________________________

23
(iii) Define the term ‘cathode’
______________________________________________________________________________
______________________________________________________________________________
(iv) Predict the ion from (c) (ii) which will migrate to the cathode
______________________________________________________________________________
______________________________________________________________________________
(v) Is ethanoic acid a strong or weak electrolyte? Explain your answer.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________

24
CHEMISTRY
GRADE 10
WEEK 8 LESSON 3
Topic: Review of Acids, Bases and Salts
(a) Phosphoric acid, H3PO4, is a common additive in most soft drinks. It can react with
sodium hydroxide, an alkali, to form both normal and acid salts.
(i) Define the term ‘acid’ and ‘alkali’.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(ii) Define the terms ‘acid salts’ and ‘normal salts’
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________

25
(iii) State the molecular formula for the normal salt formed from the reaction between
phosphoric acid and sodium hydroxide.
______________________________________________________________________________
(iv) Write a balanced equation to show the formation of the normal salt stated in (a) (iii).
______________________________________________________________________________
(v) State the molecular formula for an acid salt formed from the reaction between phosphoric
acid and sodium hydroxide.
______________________________________________________________________________
(vi) Write a balanced equation to show the formation of the acid salt stated in (a)(v)
______________________________________________________________________________
(b) A solution of 0.05 M phosphoric acid has a pH of 4, and a solution of 0.05 M sulphuric
acid has a pH of 1.
Which of the two acids is stronger?
______________________________________________________________________________

26
(c) Jeffrey complains of pains due to excess stomach acid after consuming too much orange
juice.
(i) Name TWO acids present in orange juice.
______________________________________________________________________________
(ii) State the type of chemical reaction that takes place in the treatment of excess stomach
acid
______________________________________________________________________________
(iii) Hence, name ONE substance that can be used to treat excess stomach acid
______________________________________________________________________________

27
CHEMISTRY
GRADE 10
WEEK 9 LESSON 1
Topic: Review of Energetics
(a) When a reaction is accompanied by energy changes, it can be categorized as either
endothermic or exothermic.
(i) Distinguish between the terms ‘endothermic’ and ‘exothermic’
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(ii) Generally, when chemical reactions take place, existing bonds are broken and new bonds
are formed. Classify bond making AND bond breaking as either exothermic or
endothermic processes.
______________________________________________________________________________
______________________________________________________________________________

28
(b) In an experiment, when 12.0 g of potassium nitrate, KNO3, is dissolved in 100 cm3
of
water, the temperature drops by 4.20 0
C.
(i) Calculate the number of moles of KNO3 used in the experiment.
(RMM: KNO3 = 101)
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(ii) Calculate the heat change for the reaction
Specific heat capacity of water = 4.2 J g-1 0C-1; Heat change = m x c x ΔT;
Density of water = 1 g cm-3
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(iii) Calculate the enthalpy change for 1 mole of potassium nitrate
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________

29
(iv) List TWO pieces of apparatus necessary to conduct the experiment in a school laboratory.
State how EACH piece of apparatus is used.
______________________________________________________________________________
______________________________________________________________________________
(v) Draw a labelled energy profile diagram to represent the enthalpy change for the reaction.
On your diagram, indicate the sign of ΔH for the reaction.

30
CHEMISTRY
GRADE 10
WEEK 9 LESSON 2
Topic: Review of Atomic Structure and Oxidation – Reduction reactions
(a) The element chlorine, 17Cl, with electronic configuration 2,8,7 has TWO main isotopes,
namely chlorine – 35, Cl and chlorine – 37, Cl.
(i) Define ‘isotopes’
______________________________________________________________________________
______________________________________________________________________________
(ii) Hence, show by calculation that chlorine – 35 and chlorine – 37 are isotopes.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(b) Some elements have isotopes that are unstable and radioactive. These are known as
radioisotopes. State TWO uses of radioisotopes.
______________________________________________________________________________
______________________________________________________________________________

31
(c) A student, while investigating the reactions of chlorine, bubbles chlorine gas into an
aqueous solution of potassium iodide and deduces that the potassium iodide was oxidized
because a colour change occurred.
(i) Write a balanced chemical IONIC equation for the reaction that is responsible for the
colour change.
______________________________________________________________________________
(ii) Describe the colour change that the student observed.
______________________________________________________________________________
______________________________________________________________________________
(d) Sulphur is an element that is bright yellow, and burns in air to give an acidic gas with a
choking smell.
(i) Write a balanced chemical equation, with state symbols, for the burning of sulphur in air.
______________________________________________________________________________
(ii) State ONE use of sulphur
______________________________________________________________________________
(iii) Sulphur is in the same group as oxygen and so undergoes similar reactions. Write a
balanced chemical equation, with state symbols, for the reaction of magnesium with
sulphur.
______________________________________________________________________________

32
CHEMISTRY
GRADE 10
WEEK 9 LESSON 3
The circuit below can be used to test if a substance conducts electricity.
(a) Define electrolysis
______________________________________________________________________________
(b) Describe the effect that EACH of the following substances will have on the bulb, when
the substance is placed in the empty container. State a reason for your answer for EACH
substance.
(i) Solid sodium chloride
______________________________________________________________________________
______________________________________________________________________________

33
(ii) 1 mol dm-3
hydrochloric acid
______________________________________________________________________________
______________________________________________________________________________
(iii) Ethanol
______________________________________________________________________________
______________________________________________________________________________
(iv) A bar of lead touching the electrodes
______________________________________________________________________________
______________________________________________________________________________
(c) A sample of molten lead bromide, PbBr2, is electrolyzed for three minutes with a current
of 6 amperes. Calculate the mass of lead that is deposited at the cathode, given that two
moles of electrons are required to liberate one mole of lead as shown in the following
equation:
Pb2+ (l) + 2 e-  Pb (l)
[Q = It; RAM: Pb = 207, F = 96 500 C mol-1]

34
CHEMISTRY
GRADE 10
WEEK 10 LESSON 1
Topic: Review of States of Mater and Mixtures & Separations
(a) Jamelia is in her room studying and smells the scent of curry coming from her mom’s
cooking in the kitchen area. She thinks to herself, “Ah! Diffusion at work!”
(i) Define the term ‘diffusion’
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(ii) Explain how the diffusion of the scent of the curry supports the particulate theory of
matter.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________

35
(iii) Diffusion is a process that can also occur in liquids. State how the arrangement of
particles in a liquid differs from that in a solid and a gas.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(iv) Apart from diffusion, identify ONE process that supports the particulate theory of matter
and state ONE example of such a process.
______________________________________________________________________________
______________________________________________________________________________
(b) Jamelia’s mom showed her that in order to cook with curry she first had to mix the curry
powder with water. Jamelia observed that the mixture resembled a chalk and water
mixture she had seen in class, except the curry mixture was brown in colour.
(i) State whether the mixture of curry powder and water is as a suspension or colloid
______________________________________________________________________________
(ii) State the MOST appropriate technique that could be used in a school laboratory to
separate this mixture.
______________________________________________________________________________

36
(iii) Draw a clearly labelled diagram of the apparatus that could be set up in the school
laboratory to separate the mixture of curry powder and water. In your diagram, show the
location of the separated components.

37
CHEMISTRY
GRADE 10
WEEK 10 LESSON 2
Topic: Review of Atomic Structure and Electrolysis
(a) Define EACH of the following terms:
(i) Atomic number:
______________________________________________________________________________
(ii) Mass number:
______________________________________________________________________________
(b) Sodium is a metal with an atomic number of 11 and mass number of 23.
(i) Draw a diagram to show the arrangement of electrons in sodium atom
(ii) State the period to which the element sodium belongs in the periodic table.
______________________________________________________________________________

38
(ii) Describe the bonding in sodium metal
______________________________________________________________________________
______________________________________________________________________________
(c) Sodium chloride is a typical salt of sodium metal. A concentrated sodium chloride
solution (brine) can undergo electrolysis when it is used as an electrolyte in an
electrolytic cell using inert electrodes.
(i) Define the term ‘electrolysis’
______________________________________________________________________________
______________________________________________________________________________
(ii) Write the half equations, including state symbols, for the reaction that occurs at the anode
and cathode during the electrolysis of concentrated sodium chloride solution (brine).
______________________________________________________________________________
______________________________________________________________________________

39
CHEMISTRY
GRADE 10
WEEK 10 LESSON 3
Topic: Review of Structure & Bonding and Periodic Table
The table below lists the chemical symbols of elements in Period 3 of the Periodic Table and
their respective atomic numbers.
Chemical symbols Na Mg Al Si P S Cl Ar
Atomic number 11 12 13 14 15 16 17 18
(a) Explain why these elements are all placed in Period 3 of the Periodic Table.
______________________________________________________________________________
______________________________________________________________________________
(b) Which element in the table forms an oxide which readily dissolves in water to give a
solution with a pH greater than 7? Write a balanced equation to support your answer.
______________________________________________________________________________
______________________________________________________________________________
(c) The element sulphur, S, can exist as different allotropes. Define the term ‘allotrope’.
______________________________________________________________________________
______________________________________________________________________________

40
(d) Draw a diagram to show the arrangement of electrons in sulphur.
(e)(i) State the type of bond that forms when sulphur reacts with chlorine.
______________________________________________________________________________
(ii) Explain why the type of bond stated in (e) (i) is formed
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(f) Write the formula of a compound which is formed when sulphur reacts with chlorine.
______________________________________________________________________________
(g) Draw a dot and cross diagram to show the bonding in the compound stated in (f)

41
CHEMISTRY
GRADE 10
REFERENCES
Caribbean Examination Council. CSEC Chemistry Past Papers (2015 – 2019). Macmillan
Publishers Limited
Hunte-King, J., Maragh, P., Nagir, F., & Norris, R. (2013). Chemistry for CSEC. United
Kingdom: Nelson Thornes Ltd.
Remy, C., Mason, L., Lambert, N., & Mohammed, M. (2007). Chemistry for CSEC. England and
Wales: Pearson Education Limited.
Taylor, M., & Chung-Harris, T. (2010). CXC Chemistry. England: Macmillan Publishers
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cxc rates.pdf

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