SURE
CASE
PASS
PHYSICAL SCIENCES
GRADE 12
CHEMISTRY (P2)
EXAM COACHING: PREPARATION AND TIPS
PREPARED BY
MR. MBAY I.B
(PHYSICAL SCIENCES EDUCATOR AT NORTHWOOD SCHOOL)
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1. HOW TO USE THE SURE CASE PASS BOOKLET
 A Pass is guaranteed if you follow all instructions in this booklet
 Select FOUR different past exam papers and their memos. Hard copies are
preferable to soft copies
 Study and practice for ONE topic at a time with the selected past exam papers
 Have an exam pad or exercise book and a pen/pencil
 Write down ALL the answers, even if you assume that you know them enough
 Consult your teacher for Clarity on aspects you do not understand
 All definitions are provided at the last pages of this booklet
2. BASIC SKILLS
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
Spare enough time to study before the exam
Associate the content of each question to the relevant topic
Read FULLY and CAREFULLY each question statement
Memorise and master ALL definitions, laws and conditions associated to the topic
Associate a formula to each definition or law (make use of the formula sheet)
Make a substitution (write numbers) after each formula
Always write the correct SI Unit for the final answer, where applicable.
Mind and Manage the time wisely
Each mark counts
ATTEMPT ALL the questions
ATTENTION:
The biggest mistake made by learners is to spend more of their study time on calculations
instead of theory.
Note that calculations involved in a FULL chemistry paper carry LESS THAN 30% of the
total mark
3. STRUCTURE OF THE PAPER
QUESTIONS
1
2
3
4
5
6
7
8
9
Total mark:
Duration:
MAIN TOPIC
MULTIPLE CHOICE QUESTIONS
ORGANIC CHEMISTRY
ORGANIC CHEMISTRY
ORGANIC CHEMISTRY
CHEMICAL CHANGE
CHEMICAL CHANGE
CHEMICAL CHANGE
ELECTROCHEMISTRY
ELECTROCHEMISTRY
150
3 Hours (180 minutes)
SUB-TOPIC
All topics
Nomenclature
Physical properties
Chemical properties
Reactions rates
Chemical equilibrium
Acids and bases
Galvanic cells
Electrolytic cells
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4. EASILY OBTAINABLE MARKS PER QUESTION
QUESTION 1
MULTIPLE CHOICE: covering all topics
a. There are 10 Multiple choice questions (1.1 to 1. 10)
b. Each question has 4 options A, B, C and D
c. Read fully and carefully the question
d. Identify which topic is assessed in the question
e. Eliminate options that are clearly incorrect, usually 2 options
f. Read again the question before choosing the correct option from the remaining 2
g. Write the chosen option letter next to the question number in your answer booklet.
h. If you are not sure about your answer, DO NOT leave a blank space. Rather guess
the answer and put a sign next to it, in case you get time to return to that question.
i.
ANSWER ALL the Multiple choice questions
QUESTION 2
ORGANIC MOLECULES: Nomenclature

Memorise the following terms and aspects
1
Name the 9 homologous series
2
Define Hydrocarbon
3
Define saturated molecule
4
Define unsaturated molecule
5
Define Homologous series
6
Define Functional group
7
Define Structural isomers
8
Define Position isomers
9
Define Chain isomers
10
Define Functional group isomers
11
Define Primary, secondary or tertiary
Alcohols/Haloalkanes

Memorise and master the general formula for each homologous series

Memorise and master the name and the structure of the functional group for each
Homologous series

Memorise and master the Suffix (ending) of IUPAC name for each homologous
series (e.g. An Alcohol name ends with –ol, An alkyne ends with –yne)

If you are sked to draw a structural formula, 1 mark is allocated for the functional
group structure, another mark for the substituents (side chain or halogen)
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
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If you are asked to Write down the IUPAC name, 1 mark is allocated for the parent
name (longest chain)

Remember that Position and Chain isomers occur for substances within the same
homologous series.

The functional group isomer for an Aldehyde is a Ketone and vice versa
The functional group isomer for a carboxylic acid is an Ester and vice versa

If you are asked to write down the balanced chemical equation for the complete
combustion of an alkane, know that the products are always CO2 and H2O (1 mark)
and the reactants always the Alkane and O2 (1 mark)

How to balance the reaction above
Step 1: Check the number of carbon atoms in the alkane
-
If the Alkane contains odd number of carbons (1, 3, 5 …), put a 1 in front of the
alkane
-
If the Alkane contains even number of carbons (2, 4, 6 …), put a 2 in front of the
Alkane
Step 2: Balance the number of carbon atoms on the right side
Step 3: Balance the number of hydrogen atoms on the right side
Step 4: Count the total number of oxygen on the right side of the equation. Divide
that number by 2 then put your answer in front of O2 on the left side
e.g.
1C3H8 + 5 O2  3 CO2 + 4 H2O
2C4H10 + 13 O2  8 CO2 + 10 H2O
Outcome
EASILY OBTAINABLE marks for question 2 is 8 MARKS
Practise
NOW try to answer 2 questions from 2 different past papers. Write down your answers.
Evaluate
Did it work? Did you score a minimum of 8 marks for each question paper?
-
If YES, TRY a third past question paper and move to question 3
-
If NO, READ AGAIN your notes and repeat this exercise
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QUESTION 3
ORGANIC MOLECULES: Physical properties

Memorise and master the following terms and aspect
1
Define Boiling point
2
Define Vapour pressure
3
Define Melting point

Remember the Higher the Boiling point the Lower the Vapour pressure

Memorise and master the name of Intermolecular forces for each Homologous
series
Homologous series
Main force
Alkanes, Alkenes, Alkynes
Van der waals forces
Other forces present
(London)
Aldehydes, Ketones, Esters,
Van der waals forces
Haloalkanes
(Dipole-dipole)
Alcohols, Carboxylic acids
Hydrogen bond
(Strong dipole-dipole)

London forces
Dipole-dipole and
London forces
Remember that Hydrogen bonds are stronger than Van Der Waals forces
Van Der Waals forces (dipole) are stronger than Van der Waals forces (London)

Remember the substance that has stronger Intermolecular forces will require more
energy to overcome the force.
INCLUDE THIS STATEMENT IN EACH EXPLANATION or REASON when
comparing the Boiling Point/ Vapour pressure/ Melting point of different substances.

If the question involves an Investigation, remember the following
1) The DEPENDENT VARIABLE will always be either the Boiling point, the vapour
pressure, the melting point or Evaporation (It can be any other physical property
such as Evaporation, volatility, surface tension, viscosity…).
Read the question statement and identify which physical property the question is
referring to.
2) The INDEPENDENT VARIABLE will be ONE of the following factors:
Functional group
Molecular mass
Surface area (Side chains/ Branches) or
Polarity
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3) To identify the Independent Variable, Check which factor among the 4 factors
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listed above is DIFFERENT between the substances you are comparing
4) The CONTROLLED VARIABLE will then be 3 out of the 4 factors listed above
(E.g. If Molecular mass is the Independent variable, then the controlled variables
will be Functional group, surface area and polarity)
5) To identify the controlled variable, check which factor is the SAME for the
substances you are comparing.

If you are asked to write down an investigative Question, just say
How does the (Independent variable) affect the (Dependent Variable)?

If you are asked to write down a Hypothesis for the investigation, just say
An increase in the (Independent variable) will increase the (dependent variable)

If the question asks to explain the difference between Boiling point, Melting point or
vapour pressure, use the following point form approach
1) Write the NAME of the intermolecular force for each compound
Choose between Van Der Waals forces and Hydrogen Bond
2) State Which Substance has a stronger force than the other
3) Give a reason for the statement in point 2
The reason will depend on the INDEPENDENT variable
(Functional group, Greater molecular mass, greater surface area or more polar)
4) State that more energy is needed to overcome the stronger force.
Outcome
EASILY OBTAINABLE marks for question 3 is 7 MARKS
Practise
Now try to answer 2 questions from 2 different past exam papers. Write down your answer
Assess
Did it work? Did you score a minimum of 7 marks for each past question paper?
-
If YES, TRY a third question paper and move to question 4
-
If NO, READ AGAIN your notes and repeat this exercise
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QUESTION 4
ORGANIC MOLECULES: Chemical reactions
Memorise and master the following terms and aspects

Define cracking

Remember the following types of reactions
1) Combustion/ Oxidation (Complete or incomplete)
2) Cracking (Thermal or Catalytic)
3) Substitution (Halogenation, Hydrolysis and Alcohol  Haloalkane)
4) Elimination (Dehydrogenation, Dehydrohalogenation and Dehydration)
5) Addition (Hydrogenation, Halogenation, Hydrohalogenation and Hydration)
6) Esterification (Primary alcohol + Carboxylic acid  Ester + Water)

Remember that Esterification involves the reaction between a Carboxylic acid and
a PRIMARY alcohol as reactants to give off Ester and Water as products

Esterification requires Heat and H2SO4 as a catalyst/Dehydrating agent

Remember that Combustion reaction is a reaction between an ALKANE with
OXYGEN (O2) to produce Carbon dioxide and water

Remember that Cracking has an Alkane as the reactant, then a short alkane and
alkene(s) as products
Long Alkane

Short Alkane + Alkene(s)
There are 2 methods used for cracking
If heat is used it is called Thermal cracking
If a catalyst (another substance) is used then it is called Catalytic cracking

For Substitution, Addition and Elimination, only 4 homologous series will be
involved:
3 saturated molecules (Alkanes, Haloalkanes and Alcohols) and
1 unsaturated molecule (Alkene)

For Substitution reaction, there are 2 reactants (1 saturated Organic and 1
inorganic) and 2 products (1 saturated Organic and 1 inorganic)

For Addition reaction, there are 2 reactants (1 unsaturated organic and 1 inorganic)
and 1 Product (saturated Organic).
But this organic product may have 2 variants; the MAJOR and the MINOR products.
The major Product is the one that obeys Markovnikov rule
The minor product is the one that goes against the rule
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For Elimination reaction, there is only 1 reactant (saturated organic) and 2 products
(1 unsaturated organic and 1 inorganic)

The unsaturated organic product may have 2 variants, the Major and the minor.

How to interpret the FLOW DIAGRAM
Let us use the flow diagram below as an example
1) The ARROW indicates which substance is a reactant and which one is the
product. It points from the reactant to the product.
-
In reaction I, Compound X is a reactant and Y a product.
-
In reaction II, Compound Y is a reactant and X a product
2) A compound written next to the arrow indicates a reactant or a catalyst:
-
In reaction I, HCl is a reactant. This means Compound X reacts with HCl to form
compound Y
-
In reaction II, Compound Y reacts with H2O to form compound X in the presence of
H2SO4 as a catalyst.
3) For addition, Substitution and elimination, the number of carbon atoms in
compound X is the same as the number of carbon atoms in compound Y and
Vice versa.
4) If Compound X is a saturated compound (Alkane, Haloalkane or Alcohol) and
compound Y also a saturated compound, then reaction is SUBSTITUTION
5) If Compound X is Unsaturated (Alkene) and Compound Y saturated, then
reaction I is ADDITION and reaction II is ELIMINATION
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
When Haloalkanes react with a strong base such as NaOH or KOH, there are two
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possibilities:
-
If the strong base is dilute, the Haloalkane undergoes Substitution and the product
will be an Alcohol
-
If the strong base is concentrated, the Haloalkane undergoes Elimination and the
product will be an Alkene and HX (where X is a halogen: F, Cl, Br or I)

Memorise and master ALL the reaction conditions.
Tips:
-
For Elimination reactions; strong heat For Substitution reactions; mild heat and for
Addition reaction; No heat
-
If an acid or a base is used: For elimination reaction; Concentrated. For
substitution and addition; Dilute
-
Ethanol is required if Haloalkane is a reactant

Memorise all the types of addition, substitution and elimination reactions

To identify whether a substance is an Alkane or an Alkene, you may add few drops
of Bromine water (brown in colour)
The substance that changes the colour (Decolourises) faster is the Alkene (addition
reaction takes place), and the one that takes more time to decolourise is the Alkane
(substitution reaction takes place)
Outcome
EASILY OBTAINABLE marks for question 4 is 7 MARKS
Practise
Now try to answer 2 questions from 2 different past exam papers. Write down your answer
Assess
Did it work? Did you score a minimum of 7 marks for each past question paper?
-
If YES, TRY a third question paper and move to question 5
-
If NO, READ AGAIN your notes and repeat this exercise
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QUESTION 5
RATES OF REACTIONS

Know, memorise and master the following terms and concepts
1
Define Exothermic reaction
2
Define Endothermic reaction
3
Define Activation Energy
4
Define Activated complex
5
Define Catalyst
6
Define Reaction rate

Draw or interpret the graph of Potential energy vs course of reaction

The value of the Activation energy is the difference between the Activated complex
value and the energy of the reactants value

The value of the Heat of the reaction is the difference between the Energy of the
products and the energy of the reactants

The Heat of reaction ΔH is positive for endothermic reaction and negative for
exothermic reaction

State the conditions for Effective collision: Particles must collide with
-
Sufficient Kinetic energy
-
Correct orientation

List all the factors that affect the reaction rate (Temperature, Concentration,
pressure, Surface area, Catalyst and the nature of reactants)

Note that mass and volume are NOT factors affecting the reaction rate but they are
directly linked to these factors.
e.g.
- The volume of a container with gases relates to pressure
- The volume of a the solvent in a solution relates to concentration
- The volume of a solid substance relates to surface area
- The mass of gas or solute for solutions relates to concentration
- The mass of a solid substance relates to surface area

If you are asked to explain an increase in reaction rate in terms of collision theory,
always mention the 3 key points in the table below for each factor
(3 marks guaranteed)
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Temperature
Concentration
Pressure
- An increase in
- An increase in
- An increase in pressure
temperature increases the Concentration increases
increases the reaction
reaction rate
the reaction rate
rate
- Increasing temperature
- Increasing concentration
- Increasing pressure
increases the average
increases the number of
increases the frequency of
kinetic energy of particles
particles that are colliding
collisions between particles
- More effective collisions
- More effective collisions
- More effective collisions
per unit time
per unit time
per unit time
Surface area (state of division) Catalyst
Nature of reactants
- An increase in surface
- Adding a catalyst
- Using a more reactive
area increases the
increases the reaction
substance increases the
reaction rate
rate
reaction rate
- Increasing surface area
- More particles have
- more particles collide
increases the number of
enough energy as the
effectively
particles that are exposed
catalyst lowers the
- More effective collisions
- More effective collisions
activation energy
per unit time
per unit time
- More effective collisions
per unit time

These factors are applied for reactants only

Some factors are limited to certain substance phases
-
Temperature, for all phases
-
Concentration, for aqueous (aq) and gases (g)
-
Pressure, for gases (g)
-
Surface areas, for solids (s)
-
Catalyst, for all phases

If the question involves an Investigation, remember the following points:
-
The dependent variable will always be the reaction rate
-
The independent variable will be ONE of the factors listed above
-
To identify the Independent Variable, Check which factor is not the same for 2
different experiments
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The controlled variable will then be the rest of the factors that are applicable to the
reaction

To calculate the average reaction rate using a graph, just calculate the gradient of
the graph from the starting point to the point where the graph starts to get horizontal

To calculate the average reaction using values in a table, calculate the change in
the amount and divide by the change in time, from t = 0 to time whereby the amount
just becomes constant.

Remember that the reaction rate is a Positive number. Insert a negative sign when
calculating reaction rate from a graph with a negative gradient.

Master how to interpret Maxwell Boltzmann Distribution curves
Temperature vs Energy
Concentration vs Energy
Catalyst vs Energy

The curve that gives a greater area after the Activation energy represents a faster
reaction (higher temperature. Higher concentration or addition of catalyst)

Calculations:
-
Use the formula 𝑛 = 𝑀
-
Use the formula 𝑛 = 𝑉𝑚
𝑚
𝑉
if mass is given or has to be calculated
when dealing with gases and molar volume of gas is
given
-
𝑛
Use the formula 𝑐 = 𝑣
when dealing with aqueous solutions or gases whereby
concentration is given or has to be calculated
Outcome
EASILY OBTAINABLE marks for question 5 is 10 MARKS
Practise
Now try to answer 2 questions from 2 different past exam papers. Write down your answer
Assess
Did it work? Did you score a minimum of 10 marks for each past question paper?
-
If YES, TRY a third question paper and move to question 6
-
If NO, READ AGAIN your notes and repeat this exercise
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QUESTION 6
CHEMICAL EQUILIBRIUM

Memorise and master the following terms
1
Define Closed system
2
Define reversible reaction
3
Define Chemical equilibrium (dynamic equilibrium)
4
Explain the use of the term “dynamic”
5
Define Homogeneous and Heterogeneous reaction
6
State Le Chatelier’s principle

List the 3 factors that affect the equilibrium position:
Temperature, concentration and pressure.

Name the ONLY factor that changes the value of the equilibrium constant Kc ; that
is Temperature

Conditions for chemical equilibrium to occur,
-
The reaction must be reversible and
-
The reaction must take place in a closed system.

There is a Forward and a reverse reaction in a reversible reaction, and it is
indicated by a double arrow ↔

Remember that with chemical equilibrium the concentration is the quantity that will
be considered. So solid (s) and pure liquid (l) substances will be ignored. Only
aqueous (aq) and gases (g) will be involved in this application.

When explaining using Le Chatelier’s principle, use the following key sentences for
guaranteed marks
-
If forward reaction is favoured, the concentration of reactants will decrease and the
concentration of products will increase
-
If reverse reaction is favoured then the concentration of reactants will increase and
the concentration of products will decrease
The table on the next page summarises answers you should give when using Le
Chatelier’s principle to explain the effect of each factor affecting equilibrium.
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TEMPERATURE
If Temperature is increased
-
If Temperature is decrease
The system favours the reaction
-
The system favours the reaction
that will decrease the temperature
-
Increase in temperature favours the
that will increase the temperature
-
Decrease in temperature favours
Endothermic reaction
-
the Exothermic reaction
Mention which reaction is favoured,
-
Mention which reaction is favoured,
forward or reverse
-
forward or reverse
Mention the change in
-
Mention the change in concentration
concentrations of reactants and
of reactants and products
products
PRESSURE
If pressure is increased
If pressure is decreased
by decreasing the volume of the container
By increasing the volume of the container
-
The system favours the reaction
-
that will decrease the pressure
-
-
Increase in pressure favours the
that will increase the pressure
-
Decrease in pressure favours the
reaction that proceeds towards the
reaction that proceeds towards the
fewer number of moles
greater number of moles
Mention the reaction that is
-
favoured, forward or reverse
-
The system favours the reaction
Mention the change in concentration
Mention the reaction that is
favoured, forward or reverse
-
of reactants and products
Mention the change in concentration
of reactants and products
CONCENTRATION
-
If concentration of a reactant is
If concentration of a reactant is
increased
decreased
The system favours the reaction
-
The system favours the reaction
that will decrease that reactant’s
that will increase that reactant’s
concentration
concentration
-
Forward reaction is favoured
-
Reverse reaction is favoured
-
Concentration of reactants will
-
Concentration of reactants will
decrease and concentration of
increase and concentration of
products will increase
products will decrease
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If concentration of a product is
If concentration of a product is
increased
decreased
The system favours the reaction
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The system favours the reaction
that will decrease that product’s
that will increase that product’s
concentration
concentration
-
Reverse reaction is favoured
-
Forward reaction is favoured
-
Concentration of reactants will
-
Concentration of reactants will
increase and concentration of
decrease and concentration of
products will decrease
products will increase

Remember that the Kc value can only change if the temperature changes.

Use the following expression/ equation to determine whether the Kc value will
increase or decrease.
[Products]
Kc = [Reactants]
And
[Reactants] ↔ [Products]
Due to the change in temperature
-
Kc value increases if forward reaction is favoured
-
Kc value decreases if reverse reaction is favoured

Interpretation of Concentration versus time graph
How to identify which factor between temperature, concentration and pressure has
been affected.
-
If there is a spike or drop on only one curve, then concentration was increased or
decreased.
-
If there is a spike or drop on all curves, then pressure was increased or decreased
-
If there Is NO spike or drop in all curves, then temperature was increased or
decreased
The graph on the next pages shows how to identify the factor that was changed
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
Interpretation of Reaction rate versus time graph
Remember the following aspects
-
At equilibrium, the rate of forward reaction is equal to the rate of reverse reaction
-
If the forward reaction is favoured, then the rate of forward reaction decreases and
the rate of reverse reaction increases
-
If the reverse reaction is favoured, then the rate of reverse reaction decreases and
the rate of forward reaction increases
-
If there is a spike or a drop in only one reaction rate curve, then Concentration of a
reactant/product has been increased or decreased
-
If there is a spike or drop for both rates, then it can be
Temperature or
Pressure (on condition that substances are gases and the total number of moles of
reactants is NOT the same as the total number of moles of products)
Outcome
EASILY OBTAINABLE marks for question 6 is 8 MARKS
Practise
Now try to answer 2 questions from 2 different past exam papers. Write down your answer
Assess
Did it work? Did you score a minimum of 8 marks for each past question paper?
-
If YES, TRY a third question paper and move to question 7
-
If NO, READ AGAIN your notes and repeat this exercise
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QUESTION 7
ACIDS AND BASES

Memorise and master the following terms
Define an Acid according to Lowry – Bronsted
Define a Base according to Lowry – Bronsted
Define an Acid according to Arrhenius
Define a Base according to Arrhenius
Define Strong acid
Define weak acid
Define strong base
Define weak base
Define Monoprotic and Diprotic acid
Define Ampholyte
Define Hydrolysis
Define standard solution
Define Indicator
Define End point
Define Equivalent point

List examples of common acids (strong and weak) and bases (strong and weak)

Learn how to identify conjugate acid – base pairs in an acid – base reaction
-
To get the conjugate acid of a substance (base), just add ONE Hydrogen (H) to the
formula (e.g. conjugate acid of HSO4- is H2SO4)
-
To get the conjugate base of a substance (acid), just remove ONE Hydrogen from
its formula (e.g. Conjugate base of H2O is OH-)

Remember that a strong base gives off a weak conjugate acid and vice versa

Remember that a strong acid gives off a weak conjugate base and vice versa

Ka and Kb values
-
An acid with a greater Ka value is stronger than one with a lower Ka value
-
A base with a greater Kb value is stronger than one with a lower Kb value

Select, with reason, a suitable indicator used for titration
-
Methyl Orange
Strong acid + weak base = Acidic solution, pH range below 7
-
Bromothymol Blue
Strong acid + strong base = Neutral solution, pH range around 7
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Phenolphthalein
Weak acid + strong base = Basic (alkaline) solution, pH range above 7

If you are asked to calculate the pH of a solution, use the formula
pH = - log [H3O+]

If a pH value is given, use [H3O+] = 10-pH to find the concentration of H3O+

Ration between [acid] and [H3O+] and ratio between [base] and [OH-]
-
For monoprotic acids (such as HCl, HBr and HNO3) the concentration of H3O+ is
equal to the concentration of the acid (Ratio is 1:1).
-
For diprotic acids such as H2SO4 the concentration of H3O+ is twice the
concentration of the acid (Ratio is 1:2)
-
Same applies for bases:
[OH-] = [NaOH], ratio is 1:1

OR
[OH-] = 2 x [Mg (OH)2], ratio is 1:2
When calculating the pH value of a base, remember the relationship between
[H3O+] and [OH-] from the Kw equation [H3O+] x [OH-] = 1 x 10-14

Acid – base reactions usually involve aqueous solutions, so the formula
𝑛
𝑐 = 𝑣 is very important. Use it!

𝐶𝑎.𝑉𝑎
𝑛𝑎
Use the formula 𝐶𝑏.𝑉𝑏 = 𝑛𝑏
Only if terms such as “…is neutralised by …” or “… titrated with…” are used in
the question statement.

If terms such as “…is added to …”, “… is mixed with…” or “…react with …”
𝑛
are used in the statement, then use the formula 𝑐 = 𝑣 instead of
𝐶𝑎.𝑉𝑎
𝐶𝑏.𝑉𝑏
𝑛𝑎
= 𝑛𝑏
In this case you have to use the ratio in the balanced equation to find which of the
acid or the base is in excess and which one is the limiting reagent.
(1 mark for the formula and 1 mark for the ratio)
Outcome
EASILY OBTAINABLE marks for question 7 is 8 MARKS
Practise
Now try to answer 2 questions from 2 different past exam papers. Write down your answer
Assess
Did it work? Did you score a minimum of 8 marks for each past question paper?
-
If YES, TRY a third question paper and move to question 8
-
If NO, READ AGAIN your notes and repeat this exercise
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QUESTION 8
GALVANIC CELLS

Memorise and master the following terms
Define Redox reaction
Define Oxidation number
Define Oxidation in terms of electron transfer
Define Reduction in terms of electron transfer
Define Oxidation in terms of Oxidation number
Define Reduction in terms of Oxidation number
Define Reducing agent
Define oxidising agent
Define Galvanic cell
Define Anode
Define Cathode

Use this set of formulae to remember some definitions
EɵCell = EɵCathode - EɵAnode
EɵCell = EɵReduction - EɵOxidation
EɵCell = EɵOxidising agent - EɵReducing agent
Notice that such as Cathode, Reduction and Oxidising agent are on the same
position for this equation. This simply means they relate.
-
Reduction takes place at the Cathode (remember RED CAT?)
-
Oxidising agent undergoes Reduction, so it gains electrons
Same applies to the associated terms; Anode, Oxidation and Reducing agent
-
Oxidation takes place at the anode (remember AN OX?)
-
Reducing agent undergoes oxidation, so it loses electrons

Master how to use the Table of Standards reduction potentials
If you use TABLE 4B:
-
The substance that appears above (on top) will undergo oxidation, and it is a
stronger reducing agent
-
The substance that appears bellow (bottom) will undergo reduction, and it is a
stronger oxidising agent

Master how to write the oxidation half – reaction, reduction half – reaction and the
net redox reaction. NEVER use a double arrow in these reactions)

State the energy conversion in Galvanic cell:
Chemical to Electrical
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Master how to identify the anode and the cathode
Use the table of standard reduction potential: TABLE 4B
The top substance is the Anode and the bottom substance is the cathode

Master how to write the Cell notation, with or without the standard conditions

Memorise the standard conditions
250C for temperature, 1 mol.dm-3 for concentration and 1 atm (101, 3 kPa) for
pressure if a gas is used

Voltmeter or Ammeter reading versus Le Chatelier’s principle
-
Is ZERO when the reaction has reached equilibrium
-
Increases if the forward reaction is favoured
-
Decreases if the reverse reaction is favoured

Remember and memorise the following aspects
-
The reaction in galvanic cells is spontaneous
-
There are Two half-cells (two different electrolytes)
-
The reaction is Exothermic
-
Electrons move from the anode to the cathode
-
The anode is negative and the cathode positive
-
Platinum and Graphite (Carbon) are used as electrodes because they are Solid,
unreactive and good conductors of electricity
-
The functions of the Salt bridge
To maintain the neutrality of solutions
To complete the circuit
-
The cell potential for Galvanic cells is always positive.

Calculate the cell potential or identify an unknown metal using the formula
EɵCell = EɵCathode - EɵAnode
Outcome
EASILY OBTAINABLE marks for question 8 is 10 MARKS
Practise
Now try to answer 2 questions from 2 different past exam papers. Write down your answer
Assess
Did it work? Did you score a minimum of 10 marks for each past question paper?
-
If YES, TRY a third question paper and move to question 9
-
If NO, READ AGAIN your notes and repeat this exercise
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QUESTION 9
ELECTROLYTIC CELLS

Know, memorise and master the following terms
1
Define Electrolyte
2
Define Electrolysis
3
Define Electrolytic cell
4
Define Electroplating
All other definitions under Galvanic cells are still valid and applicable here

Remember and memorise the following aspects
-
The reaction in Electrolytic cells is Non-spontaneous
-
The reaction is endothermic
-
There is only ONE electrolyte
-
The Anode is positive and connected to the positive terminal of the battery and the
cathode is negative, connected to the negative terminal of the battery
-
There is NO salt bridge for electrolytic cells.

The question on electrolytic cells will be based on ONE of the Four applications
below: (Know and master ALL of them)
Electrolysis of Concentrated Sodium Chloride, Decomposition of copper Chloride,
Purification of copper (Electro refining of copper) and Electroplating.
1) Electrolysis of Concentrated sodium Chloride,
You have to know and memorise the following aspects
-
Chlorine ions (Cl-) will be oxidised, Water will be reduced and Sodium ions will be
the spectator ions
-
Oxidation half-reaction : 2Cl-  Cl2 + 2e-
-
Reduction half-reaction: 2H2O + 2e-  H2 + 2OH-
-
Net redox reaction without spectator ions:
-
Net redox reaction with spectator ions: 2NaCl + 2H2O  Cl2 + H2 + 2NaOH
-
Chlorine gas forms at the anode
-
Hydrogen gas forms at the cathode
2Cl- + 2H2O  Cl2 + H2 + 2OH-
As the reaction progresses:
-
The concentration of Cl- decreases
-
The concentration of OH- increases
-
The concentration of Na+ remains constant
-
The solution becomes basic (alkaline) because of the OH- formed
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2) Decomposition of copper chloride
There are Two possibilities;
-
The use of unreactive electrodes (Platinum or Carbon)
-
The use of active electrodes (Copper)

If unreactive electrodes are used, you should know and memorise the following
-
Chlorine ions (Cl-) will be oxidised, Copper ions (Cu2+) will be reduced
-
Oxidation half-reaction: 2Cl-  Cl2 + 2e
-
Reduction half-reaction: Cu2+ + 2e-  Cu
-
Net redox reaction: 2Cl- + Cu2+  Cl2 + Cu
-
Chlorine gas forms at the anode
-
Copper metal forms at the cathode, thus increases the mass of the cathode
As the reaction progresses;
-
The concentration of Cl- decreases
-
The concentration of Cu2+ decreases

If Copper is used as electrodes (anode and cathode), memorise the following
-
Copper metal Cu(s) will be oxidised, copper ions Cu2+ will be reduced and Chlorine
ions Cl- will be the spectator ions.
-
Oxidation half-reaction: Cu  Cu2+ + 2e-
-
Reduction half-reaction: Cu2+ + 2e-  Cu
As the reaction progresses,
-
The mass of the anode decreases
-
The mass of the cathode increases
-
The concentration of the copper ions Cu2+ in the solution remains the same,
because the rate of oxidation of Cu(s) is equal to the rate of reduction of Cu2+
The concentration of Cl- remains the same
3) Purification of copper (Electro refining of copper)
Memorise and master the following aspects
-
Copper containing impurities is the anode and connected to positive terminal of the
battery
-
A pure copper is used as cathode and connected to the negative terminal of the
battery
-
Copper metal Cu(s) is oxidised and copper ions (Cu2+) will be reduced
-
Oxidation half-reaction: Cu  Cu2+ + 2e-
-
Reduction half-reaction: Cu2+ + 2e-  Cu
-
Other metals at the cathode will also be oxidised
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Metal ions, such as Ag+ and Pt2+, having a stronger oxidising ability than copper will
be reduced and form a sludge at the bottom of the reaction vessel
-
The mass of the anode decreases and the mass of the cathode increases
4) Electroplating
Electroplating is coating a metal with a thin layer of another metal through
electrolysis.

Memorise and master the following aspects
-
The metal used to electroplate another metal must be the anode and connected to
the positive terminal of the battery
-
The metal to be electroplated (spoon, medal, ring…) must be the cathode and
connected to the negative terminal of the battery.
-
The metal that is used to electroplate another metal will undergo oxidation (at the
anode) and reduction (at the cathode)
-
The electrolyte must contain metal ions of the metal to electroplate with.
-
The concentration of the ions in the electrolyte remains the same because the rate
at which oxidation takes place equals the rate at which reduction takes place.
-
For example if silver (Ag) is used to electroplate a ring
Silver will be the anode and the ring will be the cathode
The electrolyte must contain Silver ions Ag+ (e.g. AgNO3)
Oxidation half-reaction: Ag  Ag+ + eReduction half-reaction: Ag + e-  Ag+
Outcome
EASILY OBTAINABLE marks for question 9 is 6 MARKS
Practise
Now try to answer 2 questions from 2 different past exam papers. Write down your answer
Assess
Did it work? Did you score a minimum of 6 marks for each past question paper?
-
If YES, TRY a third question paper
-
If NO, READ AGAIN your notes and repeat this exercise
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5. TERMS, DEFINITIONS AND LAWS
1. Molar volume of gases
3
One mole of any gas occupies 22, 4 dm at STP.
2. Boiling point:
The temperature at which the vapour pressure of a substance equals atmospheric pressure.
3. Melting point:
The temperature at which the solid and liquid phases of a substance are at equilibrium.
4. Vapour pressure:
The pressure exerted by a vapour at equilibrium with its liquid in a closed system.
5. organic molecules
Molecules containing carbon atoms.
6. Hydrocarbon:
Organic compounds that consist of hydrogen and carbon only.
7. Homologous series:
A series of organic compounds that can be described by the same general formula and each
member differs by CH2 from the next one
8. Saturated compounds:
Compounds in which there are only single bonds between C atoms in their hydrocarbon chains.
9. Unsaturated compounds:
Compounds with double or triple bonds between C atoms in their hydrocarbon chains.
10. Functional group:
A bond or an atom or a group of atoms that determine(s) the physical and chemical properties of a
group of organic compounds.
11. Structural isomer:
Organic molecules with the same molecular formula, but different structural formulae.
12. Chain isomers:
Molecules with the same molecular formula, but different types of chains
13. Positional isomers:
Molecules with the same molecular formula, but different positions of the substituents or functional
groups on the parent chain
14. Functional isomers:
Molecules with the same molecular formula, but different functional groups
15. heat of reaction (ΔH)
The energy absorbed or released in a chemical reaction.
16. exothermic reaction
A reaction that releases energy.
17. endothermic reaction
A reaction that absorbs energy
18. activation energy
The minimum energy needed for a reaction to take place.
19. activated complex
The unstable transition state from reactants to products
20. reaction rate
The change in concentration of reactants or products per unit time.
21. positive catalyst
A substance that speeds up a reaction by lowering the activation energy without itself undergoing a
permanent change.
22. closed system
A system that has no exchange of mass with its surroundings.
23. A reversible reaction:
A reaction where products can be converted back to reactants.
24. Chemical equilibrium (Dynamic equilibrium):
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A stage in a chemical reaction whereby the rate of the forward reaction equals the rate of the
reverse reaction.
25. Le Chatelier's principle:
When the equilibrium in a closed system is disturbed, the system will re-instate a new equilibrium
by favouring the reaction that will oppose the disturbance.
26. Acid (Arrhenius)
+
A substance that ionises in water to produce hydronium ions (H3O )
27. Base (Arrhenius)
A substance that dissociates in water produce hydroxide ions (OH )
28. Acid (Lowry-Bronsted)
A proton donor
29. Base (Lowry-Bronsted) :
A proton acceptor.
30. Strong acid:
+
Acid that ionises completely in water to form a high concentration of H3O ions.
31. Weak acid
+
Acid that ionises partially in water to form a low concentration of H3O ions.
32. Strong base
A base that dissociates completely in water to form a high concentration of OH ions.
33. Weak base
A base that dissociates partially in water to form a low concentration of OH ions.
34. Ampholyte (Amphoteric):
A substance that can act as either acid or base
35. Hydrolysis
A reaction between a salt and water
36. Equivalence point
A stage at which the acid /base has completely reacted with the base/acid.
37. End point
A point where the indicator changes colour.
38. Redox reaction
A reaction that involves the transfer of electrons
39. Oxidation
Loss of electrons OR Increase in oxidation number
40. Reduction
Gain of electrons OR Decrease in oxidation number
41. Reducing agent
A substance that loses electrons
42. Oxidizing agent
A substance that gains electrons
43. Anode
An electrode where oxidation takes place
44. Cathode
An electrode where reduction takes place
45. Galvanic (Voltaic) cell
An electrochemical cell in which chemical energy is converted into electrical energy.
46. electrolytic cell
An electrochemical cell in which electrical energy is converted into chemical energy.
47. Electrolyte
A solution that conducts electricity through the movement of free ions
48. Electrolysis:
The chemical process in which electrical energy is converted to chemical energy
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6. FORMULA SHEET
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