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Grade 12 Chemistry Exam Review
Lachlan Kan
January 2024

1

Unit 1

1
...
1
...
Theorised that all material was constructed out of atoms, tiny particles that could not be further
divided
...
His ideas were laughed at and overshadowed by other, more influential philosophers of his time like
Plato and Aristotle
...
1
...
Formalised Democritus’s ideas and the concept of the atom
...
Published the Atomic Theory
• Atoms are indivisible particles
...
An atom in any given same element will be exactly identical
and atoms from different elements will be distinct
...

1
...
3

JJ Thompson

1
...

2
...
A parabolic path towards the positively charged plate
was observed which indicated a constant force was applied to the particle
...

1
...
4

Ernest Rutherford

1
...
The gold foil experiment consisted of shooting positively charged α-particles into a gold foil in a room
covered in fluorescent paint
...
The
”bouncing off” was theorised to be due to the repulsion of the positively charged nucleus and the
positively charged particles
...
1
...
Theorised that electrons orbit the nucleus in energy levels (orbitals were ”quantised”) through experiments with the electromagnetic spectrum

1
...


1
...
3
...
The light passes through the slit and into a
prism
...

1
...
2

Emmission Spectrum

Energy (not light) is passed through a sample of gas
...
The prism then shines the light onto a detector, revealing which wavelengths are emmited by the
sample
...
4

Energy Levels

When energy (ex
...
Afterwards, the electron will drop back down to ground state and
in the process, emit a photon
...
This implies that certain element’s electrons can only move up a fixed distance, implying
the quantisation of energy levels
...
The energy released by emission corresponds to the distance between the levels the electron is falling
through
...
5

Quantum Model of the Atom

Electrons exist in orbitals in their corresponding energy levels
...


1
...
Always fill in every slot with one electron on the way up, then after everything is filled, fill in the
second one
2
...
Always fill electrons in order of increasing energy

1
...
The highest possible charge on any given transition metal is given by
q =N +2
where q is the charge and N is the number of unpaired electrons the element has
...
8

Isoelectricity

If 2 or more particles has the same number of electrons, they are said to be isoelectronic, for instance, Cl−
is isoelectronic with Ar since they both have 8 electrons
...
9

Electron Configuration

A representation of the location of any given element’s electrons
...
The format is as follows
nOrbitalN
Where n is the energy level and N is the number of electrons in an orbital
...


1
...
The name and angles of molecular geometry is as follows(Note that the
notation used AXn Em denotes the number of bonds as n and the number of lone pairs as m)
• AX2 : Linear, 180◦
• AX3 : Trigonal Planar, 120

◦

• AX2 E: Bent, 117◦
• AX4 : Tetrahedral, 109
...
5◦
• AX2 E2 : Bent, 104
...
5◦ , 90◦
• AX4 E2 : Square BAsed Planar, 90◦
The electron distrubution is determined by the AXE formula equivalent to AXm+n for a given molecule,
for example, XeF4 : AX4 E2
...


1
...
11
...

• Soluble in other nonpolar substances: Since nonpolar molecules only have LDVW they can replace the
LDVW in other nonpolar molecules, thus being soluble
...
Larger nonpolar molecules will be harder
to melt/boil since there are more LDVW present
...

• Not Conductive: Nonpolar molecules have neither the ions nor free electrons to be conductive
1
...
2

Polar Molecules

• Soluble in water: Since polar molecules have Dipole-Dipole (DD) forces and some can Hydrogen Bond
(HB), they can replace the H-bonds in water, thus being soluble
...

• Low melting and boiling point: Since polar molecules only have IMFs that can be very easily overcome,
they have a low melt/boil point, although still higher than nonpolar molecules (since they have the
stronger IMFs)
...

• Not Conductive: Polar molecules have neither the ions nor free electrons to be conductive
1
...
3

Metallic Solids

• Insoluble in water: Since metals are held together by metallic bonds that involves a sea of delocalised
electrons, they cannot replace the HB in water
• Malleable and Ductile: Since metals are held together by a sea of delocalised electrons that are free to
shift around and move, they are very malleable and ductile
...

• Conductive: The free delocalised electrons can flow to be conductive
4

1
...
4

Network Solids

• Insoluble in water: Since network solids are held together by a network of pure covalent bonds, they
cannot replace the HB in water
• Hard and Brittle: Since network solids are held together by pure covalent bonds that are strong and
rigid, they are very hard and brittle
...

• Conductive: Only graphite (3D network solids) is conductive
1
...
5

Ionic Solids

• Soluble in water: Since ionic solids are held together by ionic bonds, they are very polar and can
replace the HB in water
• Rigid and Brittle: Since ionic solids are held together in a crystalline structure by ionic bonds, they
are very hard
...

• High melting and boiling point: Metallic bonds are among the strongest bonds to hold a substance
together, and therefore are extremely hard to overcome, making a high melting/boiling point
...
1

Collision Theory

For a reaction to occur the following must be satisfied
• The particles must collide
• The collision geometry must be favourable
• The collision must have energy greater than the activation energy required for the reaction
And it follows that the rate of reaction will depends on
• The frequency of collisions: The more collisions that happen the faster the reaction goes (Ex
...
Catalysts lower the activation energy to increase proportion of effective collisons)

[ Reactant ]

In a reaction, the concentration-time graph for any reactant and product will be as follows

t

5

[ Product ]

t

This is because when a reaction occurs, at the beginning, there are a lot of reactants around, so it is easier
for any given particle of reactant to react with another reactant
...
In the end, there are not a lot of reactants around, and the container
is mostly occupied by products, decreasing the frequency of collisions, thus the rate slows down
...
2

Reaction Mechanisms

Reaction mechanisms are the ”steps” in which reactions occur
...
They are known as reaction
intermediates
...

Notice again that next to every mechanism, there is an energy associated with it
...
The reaction associated with this energy is known as the ”rate-limiting” or ”slow” step
...
If energy is not given, then the rate-limiting step will be the step
with the most colliding particles
...
2
...
Thus a catalyst works by reducing the activation energy for a reaction
...
Those are called ”inhibitors”
...
2
...
3
2
...
1

Quantifying Rates
Rate Law

Let the following general reaction be the slow step of an overallP
reaction
...
If they are 0 then that means their respective
reactant has no effect on rate)
...
The rate law cannot contain any reaction intermediates
...

2
...
2

Comparing Rates

The order of reaction only can be found experimentally
...
With these information, the order m can be found by rearranging the following equation
...
During the first trial, the concentration was
0
...
4 · 10−7 M
s and during the second trial, the concentration was
0
...
08 · 10−6 M
s
...
08 · 10−6
= log 0
...
1 5
...
2M, the rate constant k can be
found as follows
...

r = k[N H4+ ]1 [N O2 ]1
r
k=
+
[N H4 ][N O2 ]
1
...
2)(0
...
7 · 10−5
From this information we can write the rate law of the reaction to be r = 2
...
4

Thermochemistry

Thermochemistry is the branch of chemistry that is concerned with energy transfer in a chemical system
...

• Potential energy is energy stored within or between atoms, and those concerned with chemistry include
chemical, nuclear, and electrical potential energy
Thermal energy is a measure of the average kinetic energy of a system, while heat is the amount of energy
transferred between substances
...
5

Heat Transfer

When heat is supplied to an object, its average kinetic energy will increase
...

When heat is transferred between objects, the object with the lower temperature will have increased kinetic
energy while the object with the higher temperature will have decreased kinetic energy
...
And can be described by a modified version of the
above equation
...

−Q1 = Q2
−m1 c1 (Tf − T1i ) = m2 c2 (Tf − T2i )
T1i m1 c1 + T2i m2 c2
Tf =
m2 c2 + m1 c1
During state change, there will be energy transfer but no temperature change
...


8

2
...
A typical calorimeter includes a box of water with a lid, followed by a thermometer and
stirrer in the water
...
In a bomb calorimeter, an ignition plug is attatched to the sample to ignite the combustion
...
7

Enthalpy

Enthalpy is the total amount of energy in a system, and is denoted by ∆H
...
So therefore in all instances it must always the ”change in enthalpy”, ∆H
...
7
...
The final temperature is 50 degrees celcius
...
18)(50 − 25)
= 10450 J
∆H = −QH2 O
= −10450 J
And the molar enthalpy can simply be found by dividing the enthalpy by the number of moles of KCl
...
8

Hess’s Law

When given a reaction with all it’s mechanisms, the individual mechanisms must be scaled in order to fit
the overall reaction
...
For
example
...
We first notice that the CaO
of the first equation is on the wrong side, so we need to flip the equation
...
This yields
1
∆H = +635kJ
CaO → Ca + O2
2
We then notice that the H2 O is also on the wrong side, so we also need to flip the second equation by
multiplying it by -1
...
By inspection, the hydrogens and the oxygens should cancel out
when added together with the other equations, and the Ca(OH)2 is on the correct side, so we do not need
to do anything to it except multiply it by 1
...
Knowing that this equation is correct, we can add together the
modified enthalpies
...
9

Enthalpies of Formation and Bond Enthalpies

Enthalpies of formation are average enthalpies for the formation of each molecule
...
The bond enthalpy of the forming of one mole of a
molecule is simply the sum of bond enthalpies of the reactant that is used to make the molecule substracted
from the sum of bond enthalpies of the molecule (the product) itself
...

10

3
3
...
This equilibrium can be found
on the [ ]-t graph as the ”flatline” region
...
2

La Chatalier’s Principle

Several factors can affect the equilibrium of any given reaction
...
2
...
2
...
3

Temperature Increase

The concentrations of whichever side energy is on will decrease smoothly, while the side with no energy term
will have their concentrations increased
...
4

Pressure Increase

The concentrations of all reactants and products increases, followed by a smooth increase in concentration
in the side with less gaseous particles, and a decrease in concentration in the side with more gasous particles
...


3
...
+ rn Rn ⇆ p1 P1 + p2 P2 +
...
The equilibrium constant K for
any given reaction in the above form can be calculated as follows
Q
[Pn ]pn
[P1 ]p1 [P2 ]p2
...
[Rn ]rn
[Rn ]rn
For example, consider the following reaction
2CO2 ⇆ 2CO + O2

11

If the equilibrium concentrations are [CO2 ]=0
...
2·10−3 M,[CO]=4
...
3 · 10−3 )2 (2
...
25)2

K=

= 6
...
6

Reaction Quotient

For every reaction, the concentrations of the reactants and products in it’s current state can be represented
by a reaction quotient (Q), which works the exact same way as the equilibrium constant, except the concentrations are current concentrations instead of equilbirium concentrations, and the system is said to be
in equilibrium if Q = K
...
[Pn ]pn
Q
Q=
=
r
r
r
1
2
n
[R1 ] [R2 ]
...
20M, [O2 ]=3
...
3·10−3 M, the equilibrium
constant would be
[CO]2 [O2 ]
[CO2 ]2
(1
...
2 · 10−3 )
=
(0
...
4 · 107
In general, if Q < K, the system will want to increase Q to reach equilibrium, so the system will shift towards
the product side, and if Q > K, the system will want to decrease Q to reach equilibrium, so the system will
shift towards the reactant side
...
7

Equilibrium Calculations

Find the equilibrium concentration for the following reaction, K = 4
...
25M , [N2 O4 ] = 0M
N2 O4 ⇆ 2N O2
We first see that Q > K, since there are no reactants, Q → ∞, so the reaction must shift left, therefore
we implement a change variable ϕ
...
25M
−2ϕ
0
...
25 − 2ϕ)2
4
...
25 − 2ϕ)2
4
...
1
K=

Note that for every polynomial, there may be multiple roots, but only one is valid, so the other one will be
dismissed
...
25 − 2ϕ = 1
...
1M

3
...

• In Bronstead-Lowry Theory, an acid ionises in water to donate protons and a base ionise in water to
accept protons
...
9

pH and pOH

pH and pOH are a measure of the concentration of H + and OH − ions respectively, and are defined as follows
pH = − log [H + ]
pOH = − log [OH − ]
In water, the following reaction is constantly at equilibrium
2H2 O ⇆ H + + OH −

And we can write the equilibrium constant as follows
K = [H + ][OH − ]
Since there is no concentration of water, the water term is omitted
...
00 · 10−14
...
Substituting this value and then taking the negative log of both
sides gives
1
...
For example, in a solution of 2
...
0M
14 = pH + pOH
pH = pOH − 14
= 14 − log [OH − ]
= 14 − log 2
...
70
Note that in base-10 logarithms, the integer part of the solution are not significant, so 2 sig-figs will mean 2
decimal places
...
10

Acid and Base Constants

For weak acids and bases, finding pH and pOH is not that straightfoward
...
In most cases, the KA is given,
and the pH is found by simply rearranging for [H3 O+ ], since [H3 O+ ] = [H + ]
...
Choose [HCN ] = 0
...
9 · 10−10
HCN + H2 O ⇆ CN − + H3 O+
We begin by constructing an ICE table
I
C
E

[HCN ]
0
...
25−ϕ

[CN − ]
0
+ϕ
+ϕ

[H3 O+ ]
0
+ϕ
+ϕ

We notice that the concentration of hydrocyanic acid is far greater than the KA , and the ratio between them
far exceed 500, therefore we can say that 0
...
25
...
25
√
ϕ = 4
...
25

4
...
1 · 10−5
Plugging this back into the concentration and pH equations we can easily find the pH
[H3 O+ ] = ϕ = 1
...
1 · 10−5 = 4
...
In most cases, the KB is given,
and the pH is found by simply rearranging for [OH − ] and putting it into the equation that relates it with
pH
...
Choose [N H3 ] = 0
...
8 · 10−5
N H3 + H2 O ⇆ N H4+ + OH −
The ICE table is as follows
I
C
E

[N H3 ]
0
...
25−ϕ

[N H4+ ]
0
+ϕ
+ϕ

[OH − ]
0
+ϕ
+ϕ

We notice that the concentration of ammonia is far greater than the KB , and the ratio between them far
exceed 500, therefore we can say that 0
...
25
...
25
√
ϕ = 1
...
25

1
...
7 · 10−6
Plugging this back into the concentration and pH equations we can easily find the pH
[OH − ] = ϕ = 6
...
7 · 10−6 = 8
...

This rule also applies to bases and their conjugate acids
...
11

Buffer Solutions

A buffer solution is made with a weak acid/base with its respective ion in an aqueous solution
...
A general buffer solution of an acid can be represented as follows
HA + H2 O ⇆ A− + H3 O+
Buffer solutions are only effective if the pH is in an effective range, in which pH = pKA ± 1
...
For example, consider a buffer made of 0
...
09 · 10−2 M
[CH3 COO− ]
[CH3 COOH]
6
...
74 + log
0
...
53

pH = pKA +

When [OH − ] is added to a acid buffer solution, the system will seek to compesate by shifting right to
produce more [H3 O+ ], whereas when [H3 O+ ] or [H + ] is added to a acid buffer solution, the system will
seek to compensate by shifting left to produce less [H3 O+ ]
...
where when [OH − ] is added to a basic buffer solution, the system will seek to compesate
by shifting left to produce less [OH − ], whereas when [H3 O+ ] or [H + ] is added to a basic buffer solution,
the system will seek to compensate by shifting right to produce more [OH − ] to balance out the pH change
...


3
...
Where pH1 is simply the pH of
the sample, pHf is the pH of the titrant, and Veq is the volume calculated by using the equation
Veq =

csample Vsample
ctitrant

The equilibrium pH will change depending on how strong the conjugate acids and bases of the sample and
titrant are
...
If they are
equal, equilibrium pH=7
...
1

Unit 4
Hydrocarbons

Every organic compound contains carbon because carbon has a small atomic radius and can form up to
4 bonds
...
Aromatic hydrocarbons contains benzene rings while aliphatic ones do not
...
2

Alkanes

Alkanes are made of chains of CH2 single bonded with each other with a CH3 at each end
...
) depending on the number of carbons in the chain, and are
named with an -ane ending
...
So it is called butane
...
3

Alkenes

Alkenes are hydrocarbons with double bonds
...
If there are more than one double bond, list all
of them in ascending order followed by ”-ene” with a number prefix (ex
...
For example,

There is a double bond in the second carbon, and there are 4 carbons in total, so its but-2-ene

4
...
They are named like alkenes except the ”-ene” ending is
changed to ”-yne”
...
5

Side Chains and Other Naming Rules

To name a side chain, simply put the number of the side chain’s carbon and then the side chain with the
”-yl” suffix (ex
...
Special names include the iodine side chain: iodo-, chlorine side chain:
chloro-, the fluorine side chain: fluoro-, the nitrogen side chain: nitro, the benzene side chain, : phenyl-, and
the isopropyl side chain: isopropo-
...
Names should be ordered in alphabetical order and alkynes should be given
priority over alkenes which has priority over alkanes when numbering carbons
...
An example of naming is as follows
N

The main chain has 4 carbons, there is a methyl group on the second carbon and a nitro group on the third
...
So this is 2-methyl-3-nitrobut-2-ene
...
6

Properties of Hydrocarbons

• Insoluble in water: Since nonpolar molecules only have London Van der Waals (LDVW) forces they
cannot replace the H-bonds in water, thus being insoluble
...

• Low melting and boiling point: Since nonpolar molecules only have LDVW, which is the weakest of
all the IMFs, it can be very easily overcome and melt/boil
...
Note that Alkynes has a higher boiling point than
alkanes which has a higher boiling point than alkenes
...
Since better packing means that they are closer together and thus the LDF are stronger
...
Alkynes are more reactive than
alkenes which are more reactive than alkanes
...

17

4
...
7
...

4
...
2

Hydrohalogenation
+HI −→
I

Note that in hydrohalogenation, Markovnikov’s rule apply, meaning that the hydrogen will always take the
outer carbon (the carbon with the most hydrogen already attatched to it)
...
7
...

4
...
4

Hydration
6M H +

+H2 O −−−−−→
OH
Note that in hydration, Markovnikov’s rule still applies as the H2 O seperate into H and OH and forms a
secondary alcohol
...
8

Cyclic Hydrocarbons

Cyclic hydrocarbons are hydrocarbons that forms a ring
...
Small molecules like cyclopropane are prone to breaking since they have a lot of steric strain
...
The following is an example
in naming
...

18

4
...
9
...

4
...
2

Geometric Isomers

Geometric isomers are molecules that only differ by rotation about a C=C bond
...
The left one is the E-Isomer
and the right one is the Z-Isomer
...
9
...
The higher
the proton count, the higher the priority
...
If they are on different sides, It is the E-Isomer
...
10

Alcohols

Alcohols are hydrocarbons with the functional group −OH attatched as the highest priority group
...
Alcohols are granted the
highest numbering priority
...
For example
OH
This has a double bond at 2 and an OH group at one
...
11

Reactions of Alcohols

Alcohols can undergo elimination to return to an alkene as follows
12M H SO

2
4
OH −−−−−−−−→

+ H2 O

Alcohols can also be oxidised to become either an aldehyde or a ketone, which will be discussed later
...
11
...

• 2◦ Alcohol: −OH attatched to CH, can react once and will react in both the oxidation and the lucas
test
• 3◦ Alcohol: −OH attatched to C, cannot react but will only react in the lucas test
19

4
...
But among
themselves, their only IMF is DD
...
Aldehydes are
named with the ”-al” suffix and a number should be added under no circumstances
...
Therefore it is called butanal
...
12
...
13

OH

Ketones

Ketones are formed by the oxidation of a 2◦ alcohol as follows

OH

O

K2 Cr2 O7 , H +

−−−−−−−−−→
Since Ketones stll has the oxygen, they can H-Bond with water and thus have high solubility
...
Ketones are granted the highest numbering priority
...
For example
O

This has 4 carbons and has a =O at its 2nd carbon
...

4
...
1

Reactions of Aldehydes

Ketones can be reduced to a 2nd degree alcohol in a hydrogenation (reduction) reaction
O

OH

+ H2

∆,HP,N i/P d/P t

−−−−−−−−−−−→
20

4
...

carboxylic acids are granted the highest numbering priority
...
For example
OH

O
This has the carboxyl group and has 4 carbons
...
14
...
For example,
the above would be called potassium ethanoate
...
15

Polymers

The only polymers studied in this course are addition polymers
...
And in an addition reaction, all the reactants must turn into the desired product and none are
leftover
...
Examples of polymers include PTFE, PVC,
polyethene, polystyrene and polypropene
4
...
1

Crosslinking

Polymers can crosslink with other polymers to create larger polymers
...
Crosslinking creates more covalent bonds and thus makes the
resultant polymer more rigid than before
...
16

Common Names of Organic Compounds

• 1-methylbenzene: xylene
• 1,2-dimethyl benzene: o-xylene
• 1,3-dimethyl benzene: m-xylene
• 1,4-dimethyl benzene: p-xylene
• 2-methyl-1,3,5-trinitrobenzene: trinitrotoluene
• propan-2-one: acetone
21

• methanal: formaldehyde
• methanoic acid: formic acid
• ethanoic acid: acetic acid
• ethandioic acid: oxalic acid
• benzenol: phenol
• citric acid (IUPAC name not taught)
• propan-1-2-3-triol: glycerol
• ethanol: ethyl alcohol
• propan-2-ol: isopropanol

5

Unit 5

5
...
Redox reactions convert chemical potential energy into electrical energy through the movements
of electrons
...
For example, consider the following
reaction
Zn + I2 → ZnI2
To find out the oxidising and reducting agents, the above equation must be written in its net ionic form
Zn + I2 → Zn2+ + 2I −
Now it becomes clear that zinc lost electrons and iodine gained electrons
...
We also see that the electrons from zinc has gone to iodine
...
The neutral atom and the
ion of the same element in a redox reaction is known as a redox couple
...

5
...
1

Charge and Oxidation states

An oxidation state is the charge an atom in a covalent bond would have if the bond was broken and all the
electrons went to the more electronegative atom, and are often denoted with the sign before the number
...
but for other atoms, their oxidation state will need
to be solved for
...
For example, the oxidation state for sulfur in H2 SO4 can be easily solved as follows (Note that the
oxidation state of atoms are denoted by Sn , where n is the atom)
2SH + SS + 4SO = 0
SS = −4SO − 2SH
= 0 − 4(−2) − 2(+1) = +6
And the oxidation state of sulfur SS is determiend to be +6
...
2

Balancing Reactions for Charge

Balancing reactions for charge consists of writing the reaaction in terms of its oxidation and reduction half
reactions, and then multiplying the equations by a factor such that the electron terms cancel out when the
equations are added back together
...

HN O3 + H3 AsO3 → N O + H3 AsO4 + H2 O
By solving for the oxidation states, it becomes clear that the hydrogen and oxygen are not part of the redox,
and only the arsenic and nitrogen are
...
Which gives the
following
2N +5 + 6e− → 2N +2
3As+3 → 3As+5 + 6e−
Adding together the equations and simplifying, we find that the net ionic equation represents the actual
equation
...

2HN O3 + 3H3 AsO3 → 2N O + 3H3 AsO4 + H2 O
Thus the equation has been balanced for charge
...
When balancing for mass after charge do not alter the
ratio of coefficents in the atoms that are involved in redox
...
2
...
For example
V O2+ + Zn → V O2+ + Zn2+
Fully balancing for charge gives
2V O2+ + 2Zn → 2V O2+ + Zn2+
Which is not balanced in terms of mass
...
Generally, add H2 O to one side
first and if needed, multiply the H2 O and add a required amount of H + to the other side (H2 O and H +
cannot be on the same side)
...
3

Reactivity

The reactivity of an atom is determined by its standard reduction potential (E θ , measured in volts)
...
For example, lead has
E θ = −0
...
80, and since silver has the higher potential, it is more likely to be
reduced
...


5
...
They usually contain a cathode and an anode connected by a wire (the external circuit, usually with
a voltmeter attatched) and a salt bridge (a ”bridge” filled with a salt solution, usually potassium nitrate
to prevent depolarisation)
...
if the electrode is made of Cu, then the solution will be full of Cu2+ ions, usually in
the form of a nitrate solution, like Cu(N O3 )2 )
...
Electrons typically
flow from the anode solution into the anode electrode, then into the wire before travelling into the cathode
electrode and into the cathode solution
...
4
...
The anode is negatively
charged and houses the metal that is being oxidised
...
Note that some voltaic cells are uses gasses (like hydrogen) and need an inert electrode
(like platinum) to work
...

5
...
2

Standard Electrode Potential

θ
The standard electrode potential (SHE or Ecell
) is obtained by the following formula
θ
θ
θ
Ecell
= Ecathode
− Eanode

For example, the silver-lead cell in the above example’s SHE can be calculated as follows
θ
θ
θ
Ecell
= Ecathode
− Eanode
= 0
...
13V )

= 0
...


5
...
3

Standard Cell Notation

A quick way to represent voltaic cells is through the standard cell notation
...
If an inert
electrode is used, simply write the inert electrode after a comma after the atom is mentioned

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