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 Loss of electrons
 Gain of electrons
 Increase in
 Decrease in
oxidation no.
oxidation no.
oxidation
reduction
__ , __ || __ , __
order of species is
in cell diagrams*,
direction of
the right-hand cell
electron flow in
is written as ___.
external circuit
*by convention
from anode to
cathode
reduction
completes the
suitable salt solution
circuit by allowing
for making salt
the movement of
bridge ||
ions AND equalises
written ...
the charge
diagram of a cell (not
R , O || O , R
potassium nitrate
role of salt bridge
the same as a cell
diagram!!)
Redu
Ction occurs
Oxid
Aton occurs
when written in
Eo(RHE) – Eo(LHE)
format Cu2+,Cu the
left species is __ ,
at the ..
at the..
Cathode
Anode
Eocell
the species that
the species that
OIL RIG
causes another
causes another
Or
element to increase
element to decrease
LEO the lion says
in oxidation no
in oxidation no
GER
an oxidising agent
a reducing agent
number assigned to
an atom or ion to
describe its relative
state of oxidation
or reduction
oxidation number
right species is __
oxidised form,
reduced form
mnemonic for redox
reactions
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 Balance atoms (that are

Balance atoms (that are
not H or O)
not H or O)
 Balance O (add water)

Balance O (add water)
 Balance H (add H+)

Balance H (add H+)
 Balance charge (add e- to

Balance charge (add
e-
to
more + side)
more + side)
 Add OH- to both sides to
cancel out H+’s -make H2O
balancing half
balancing half
equations – acidic
equations – alkaline
conditions
conditions
a chemical reaction
which results in the
loss of electrons
from a chemical
species
oxidation
the process by
which ionic
compounds are split
into their atoms
using electric
currents
electrolysis
Reaction at RHE as
Reaction at LHE as
drawn here
drawn here
oxidation
reduction
a chemical species
a chemical reaction
that has the ability
which results in a
to take electrons
chemical species
from other
gaining electrons
chemicals – i.e. it
causes oxidation
reduction
oxidant
oxygen,
hydrogen,
permanganate,
thiosulfate, iron(II),
dichromate, iron(III),
halides, zinc,
halogens, bromate,
oxalate, sulfur
iodate... are all …
dioxide... are all…
oxidising agents
reducing agents
Standard E°
elements in pure form;
Standard E°
potentials are
potentials are
measured with
K; concentrations 1.0
measured at a
respect to the
mol L–¹; Pressure of
pressure of ___ kPa.
standard ___ halfcell.
101.3
hydrogen
a chemical species
that has the ability to
give electrons to
another species – i.e.
it causes reduction
reductant
strongest RA is…
Na
Temp. 25 °C or 298
gases 1.0 atm or
101.3 kPa
standard conditions
strongest OA …
MnO4-
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blue solution
copper(II), Cu2+
pale orange solution
Fe3+(aq) iron (III)
solution
brown gas
NO2 gas nitrogen
dioxide
orange solution
dichromate, Cr2O72-
orange-brown
solution
I2, iodine solution
pale green solution
Fe2+(aq) iron (II)
solution
blue/green solution
purple solution
chromium(III) ion,
permanganate(VII),
Cr3+
MnO4-
In
Zn(s)|Zn2+
green solution
colourless solution
manganate (VI),
Cl-, Br-, I-, Mn2+, IO3-, BrO3-,
MnO42-
When two half-cells
are connected with a
voltmeter we
measure the _____
electromotive force
(emf of the cell)
SO32-, SO42-, C2O42-, S2O32-,
S4O62-,
H+
(red)-orange
solution
Bromine solution, Br2
the |
represents the
phase boundary
if two species are
H+/H2 half-cell
emf of zero
is called the...
IUPAC convention
Zn(s)|Zn2+(aq)||Cu2+(aq)|Cu(s)
both present in a
single solution, we
separate them
with a _____
standard half-cell
‘cell diagram’
Comma ,
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Left hand electrode
Zn(s)|Zn2+(aq)||
Right hand
electrode
Pt(s)|H2(g)|H+(aq)||
||Cu2+(aq)|Cu(s)
Inert Pt
reduced | oxidised ||
||Cl–(aq)|Cl2(g)|Pt(s)
|| oxidised | reduced
electrode placed to
the outside
Observation @ LHE
Observation @ RHE
Copper plated
Fe electrode gets thinner,
electrode, colour of
solution becomes more
solution fades
green (pale)
What emf could be
made from this cell?
Inert Pt electrode
placed to the outside
Can Fe3+ oxidise Cl- to
chlorine Cl2?
No (spontaneous
Eo(cell) = +0.32V
reaction is Cl2
oxidises Fe2+ to Fe3+)
K2MnO4
MnO2
spontaneous
reaction is.....
H2O2 → O2 + H2O
(unbalanced)
strongest to
weakest reductant
Zn > Ga > Fe
as zinc can reduce both Ga3+
and Fe2+
strongest OA is
MnO4oxidation numbers
of Mn are
H2O2
+6, +4, +7
When looking at 2
When looking at 2
std redox potentials
std redox potentials
reduction (L  R)
oxidation (L  R)
occurs in the more
occurs in the more
___ of the pair
___ of the pair
positive
negative
standard cell
diagram is...
Fe | Fe2+ || Cu2+ | Cu
RED CAT
AN OX
reduction @cathode
oxidation @anode
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Test for chlorine
gas... with starchiodide paper; colour
change is....
starch-iodide paper
turns blue-black
Cu(s)|Cu2+(aq)||Cr2O72-
Cu(s)|Cu2+(aq)||Cr2O72-
(aq)|Cr3+(aq)
(aq)|Cr3+(aq)
Eocell = +ve
Eocell = +ve
___ to move from
What would you see
What would you see
one half-cell to the
in the LHE?
in the RHE?
other
Cu electrode shrinks,
solution goes darker
blue
solution goes from
orange to blue/green
a salt bridge
provides a path for
ions
draw (write) the cell
draw (write) the cell
draw (write) the cell
draw (write) the cell
diagram
diagram
diagram
diagram
Zn|Zn2+||Ag+|Ag
Pb|Pb2+||Fe3+,Fe2+|C
Cu(s)|Cu2+(aq)||MnO4–(aq),
Pt(s)|Cl–(aq)|Cl2(g)
Mn2+(aq)|C(s)
||BrO3–(aq), Br2(aq)|C(s)
platinum or
graphite is used as
an _____ electrode
for many half-cells
inert
E° (Cr2O72-,Cr3+)=1.33 V
an oxidising agent oxidises
E° (Hg2+/Hg)= 0.85V
something else. Oxidation
E° (Fe3+,Fe2+)= 0.77V
is loss of electrons (OIL
E° (I2,I-)= 0.54V
RIG). An oxidising agent
E° (S/S2-)= -0.48V
takes electrons from that
What’s the strongest
other substance...
...so an oxidising
agent must gain
electrons.
reductant?
standard hydrogen
electrode
S2-
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OXIDANT
OXIDANT
O2
is reduced to….
Cl2 (pale green)
is reduced to….
Oxide ion O2-
Chloride ion Cl-
Iodide ion I-
Iron(II) ion Fe2+ (pale
green)
OXIDANT
OXIDANT
OXIDANT
H+ (with metals)
is reduced to….
MnO4- (in acidic
conditions)
is reduced to….
MnO4- (in basic
conditions)
is reduced to….
MnO4- (in neutral
conditions)
is reduced to….
Hydrogen gas, H2
Manganese(II) ion
Mn2+
Manganate(VI) ion
MnO42- (green)
Manganese dioxide
(brown ppt) MnO2
OXIDANT
OXIDANT
OXIDANT
(blue)
is reduced to….
Cr2O72- /H+
(orange) is
reduced to….
Copper (metal) Cu
(pinky orange)
Chromium(III) ion
Cr3+ (greeny blue)
OXIDANT
OXIDANT
IO3is reduced to….
MnO2
is reduced to….
Iodine I2 (orange
brown)
Manganese(II) ion
Mn2+
Cu2+
OXIDANT
OXIDANT
I2 (orange-brown) Fe3+ (pale orange)
is reduced to….
is reduced to….
OXIDANT
OClis reduced to….
Chloride Cl-
OXIDANT
Conc. HNO3 (NO3ion)
is reduced to….
Nitrogen dioxide gas
NO2 (brown)
Oxidation number Oxidation number
of underlined
of underlined
element
element
CuSO4
S4O62-
+6
+2.5
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REDUCTANT
REDUCTANT
REDUCTANT
REDUCTANT
Metal e.g. Mg
is oxidised to….
C (black)
is oxidised to….
CO
is oxidised to….
Fe2+(pale green)
is oxidised to….
Metal ion e.g. Mg2+
CO or CO2 gas
CO2 gas
Iron(III) ion Fe3+
(pale orange)
REDUCTANT
REDUCTANT
REDUCTANT
REDUCTANT
Bris oxidised to….
Iis oxidised to….
H2 S
is oxidised to….
SO2
is oxidised to….
Bromine Br2 (redorange)
Iodine I2 (orangebrown)
Sulfur S (yellow)
Sulfate ion SO42-
REDUCTANT
REDUCTANT
REDUCTANT
REDUCTANT
SO32is oxidised to….
S2O32is oxidised to….
H2 O2
is oxidised to….
H2C2O4
is oxidised to….
Sulfate ion SO42-
Tetrathionate ion
S4O62-
Oxygen gas O2
Carbon dioxide gas
CO2
Oxidising agents
(oxidants) are
themselves
Reducing agents
(reductants) are
themselves
reduced
oxidised
Oxidation is a loss
of …
Reduction is a
gain of …
(Leo the lion /
OIL)
(says GER / RIG)
electrons
electrons
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The oxidation
number of any
free, uncombined
element e.g. Cu,
Pb, H2, O3 and S8
is equal to….
The oxidation
number of a
simple
(monatomic) ion
e.g. Na+, Mg2+, Clis equal to ….
The SUM of the
oxidation
numbers of a
polyatomic ion
e.g. SO42-, MnO4is equal to….
In compounds the
sum of the
oxidation
numbers of all
atoms is equal
to….
Zero, 0
the charge on that
ion
the charge on that
ion
Zero, 0
The ox. number of The ox. number of
oxygen (in
hydrogen (in
If its oxidation
compounds/ions) compounds/ions) number increases,
is __ , except in
is __ , except in
the element has
peroxides where
metal hydrides
been….
it is __.
where it is __.
-2
-1
+1
-1
oxidised
If its oxidation
number
decreases, the
element has
been….
reduced
Oxidation number Oxidation number Oxidation number Oxidation number
of underlined
of underlined
of underlined
of underlined
element
element
element
element
ClO-
CrO42-
CO2
N2
+1
+6
+4
0
Oxidation number Oxidation number Oxidation number Oxidation number
of underlined
of underlined
of underlined
of underlined
element
element
element
element
SO3
H2S
NaH
KIO3
+6
-2
-1
+5
(NaH is a metal hydride)
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