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Applications of Redox Reactions Notes
(H1) analyse an electrochemical cell in terms of its components and their functions
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define and label the parts of an electrochemical cell
electrode
 conductor where half-reaction occurs
anode
 electrode at which oxidation occurs
 electrode receiving e- from oxidized species
cathode
 electrode at which reduction occurs
 electrode providing e- to reduced species
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determine the half-reactions that take place at each electrode of an electrochemical cell,
and use these to make predictions about the overall reaction and about
o the direction of movement of each type of ion in the cell
o the direction of flow of electrons in an external circuit
o what will happen to the mass of each electrode as the cell operates
Identify the following:
-cathode and anode and write appropriate half-reaction
-direction of electron flow
-direction of ion movement
2
Draw and label an electrochemical cell for a Cu/Cu2+ and Ag/Ag+ cell.
Draw and label an electrochemical cell for a Pb/Pb2+ and Zn/Zn2+ cell.
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determine voltages of half-reactions by analysing the voltages of several cells, with
reference to the standard hydrogen half-cell
predict the voltage (E0) of an electrochemical cell using the “Standard Reduction
Potentials of Half-Cells” table
o The tendency of electrons to flow in an electrochemical cell is called the voltage
or electrical potential (this is the half-cells ability to reduce).
o A zero point is arbitrarily assigned to the hydrogen half-cell
identify the standard conditions for E0 values
o Standard conditions imply that:
 the cell is at 25ºC
 all gases are at 101.3 kPa (1 atm)
 all elements are in there standard state (normal state at room temperature)
 all solutions have a 1 M concentration
What is the standard reduction potential for:
Cu2+ + 2 e- → Cu(s)
Hg2+ + 2 e- → Hg(l)
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predict the spontaneity of the forward or reverse reaction from the E0 of a redox reaction
Calculate the potential of the cell: Hg2+ + Cu → Hg + Cu2+
Calculate the potential of the cell: Ni2+ + Fe → Ni + Fe2+
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Calculate the potential of the cell: Fe2+ + Ni → Fe + Ni2+
Calculate the potential of the cell: 3 Ag+ + Al → 3 Ag + Al3+
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predict the cell potential when equilibrium is reached
 Operating electrochemical cells are NOT at equilibrium.
 However, it will move towards equilibrium.
Consider the reaction:
2 Ag2+ + Cu → 2 Ag + Cu2+
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If a cell contains a mixture of substances, then you have to determine which ion will
reduce or oxidized preferentially.
Note: The reaction having the highest tendency to lose electrons and the reaction having
the highest tendency to gain electrons will occur preferentially.
An iron strip is placed in a mixture of Br2(aq) and I2(aq). What is the preferred
reaction which occurs?
A beaker contains an iron nail wrapped with both a piece of copper wire and a piece
of magnesium ribbon, immersed in an aqueous solution containing CuSO4 and some
dissolved Cl2(g). What is the overall preferred reaction?

construct an electrochemical cell
o addressed in labs
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(H2) describe how electrochemical concepts can be used in various practical applications

give examples of applications of electrochemical cells, including lead-acid storage batteries,
alkali cells, and hydrogen-oxygen fuel cells, and explain how each functions
Lead-Acid Storage Battery (car battery)
o Consists of alternating Pb(s) and PbO2(s) plates immersed in H2SO4(aq).
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The anode reaction is:
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The cathode reaction is:
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The overall reaction is:
The above reaction occurs when the battery is discharging:
The reverse reaction occurs when the battery is charging:
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Alkali Cells
o These are our typical disposable or rechargeable batteries.
o They are called alkali because the electrolyte (KOH) is alkaline (basic).
Hydrogen – Oxygen Fuel Cells
o A fuel cell is a device in which fuel in continuously fed into the system and from
which electricity is continuously obtained from the system.
o This is different from the above battery examples where the batteries contained all
the chemical reactants within themselves.
o Hydrogen – oxygen fuel cells are around 70 – 80 % efficient, pollution free, and
operate silently. However, the electrodes corrode easily and require constant
maintenance, their expensive to make, and a large cell is required to generate
significant amounts of power.
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(H3) analyse the process of metal corrosion in electrochemical terms
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describe the conditions necessary for corrosion of metals to occur
o The most common form of metal corrosion is rusting (corrosion of iron).
o When water rests on ion, a spontaneous reaction occurs:
Note: The variable x in the rust deposit equation explain the different colours rust can
have since differing numbers of water molecules attached to the Fe2O3 molecule
will change the colour of the compound.
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suggest several methods of preventing or inhibiting corrosion of a metal, including cathodic
protection, and account for the efficacy of each method
o There are two general methods of corrosion protection:
1. isolating a metal from the environment
a) apply a protective layer such as paint or plastic
b) apply a metal which is corrosion resistant (such as steel or tin)
2. prevent corrosion by using electrochemical principles
a) protect a substance from unwanted oxidation by connecting it to a
substance that has a higher tendency to oxidize (connecting iron to strips
of magnesium)
b) change the conditions in the chemical surroundings to lower the tendency
of the surroundings to reduce (placing iron into a solution of NaOH
decreases the available oxygen and hydrogen)
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(H4) analyse an electrolytic cell in terms of its components and their functions
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design and label the parts of an electrolytic cell used for the electrolysis of a molten
binary salt such as NaCl liquid
predict the direction of flow of all ions in the cell and electrons in the external circuit
define electrolysis and electrolytic cell
o Electrolysis is the process of supplying electrical energy to a molten ionic compound
or a solution containing ions so as to produce a chemical change. Electrolysis
provides energy to non-spontaneous electrochemical reactions (Eº < 0).
o An electrolytic cell is an apparatus in which electrolysis occurs.
Consider the electrolysis of the binary salt NaCl in its molten form.
The anode reaction is:
The cathode reaction is:
The overall reaction is:
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design and label the parts of an electrolytic cell capable of electrolyzing an aqueous salt
such as KI aqueous (use of overpotential effect not required)
Consider the electrolysis of aqueous NaI.
There are two possible reduction reactions:
There are also two possible oxidation reactions:
Note: There are two ways to determine which reaction will happen:
I. the preferred reaction will be the one requiring the least voltage input
II. the half-reactions having the greatest tendency to reduce and the greatest
tendency to oxidize will be preferred
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write the half-reaction occurring at each electrode and predict observations based on this
information
write the overall cell reaction and predict the minimum voltage required for it to operate
under standard conditions
What products are formed at the anode and cathode and what is the overall reaction
when a solution containing NiSO4(aq) is electrolysed using inert electrodes?
Determine the minimum voltage which must be applied before the reaction occurs.
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What is the overall reaction which occurs when a 1M solution of HCl(aq) is
electrolysed using carbon electrodes?
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(H5) describe how electrolytic concepts can be used in various practical applications

explain the principles involved in simple electroplating
o Electroplating is an electrolytic process in which a metal is reduced or “plated
out” at the cathode.
o The cathode is made out of material that will receive the metal plating.
o The electroplating solution contains ions of the metal which is to be plated onto
the cathode.
The following is an example of plating a spoon with a layer of silver.
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design and label an electrolytic cell capable of electroplating an object
Design a cell to electroplate a copper medallion with nickel metal. Include in the
design the ions present in solution, the direction of ion flow, the substance used for
the anode and cathode, and the direction of electron flow when the cell is connected
to a power source.
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demonstrate familiarity with electrolytic cells in metal refining processes, including
refining of zinc and aluminum
o Electrorefining is the process of purifying a metal by electrolysis.
Consider the following electrochemical cell where impure Ni(s) (60.7% nickel) is
purified (99.9% nickel).