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Unit 13 LAB Redox
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2021-23 Unit 13 LAB Acid or Base?Investigate oxidation-reduction reactions in order to understand their many
applications in analysis.
Introduction
As an analytic technician working in the trading standards laboratories for Devon and
Somerset County Council. Recently, the trading standards officers have received a number
of complaints about counterfeit rechargeable batteries in a variety of appliances such as
cameras and toys. I have been asked to test a number of batteries that have been sent in by
worried customers. This is something new to the work carried out in my department, so I am
doing a refresher course on the theory behind the application of oxidation-reduction
reactions to applications in industry. I have been asked to write a report to demonstrate
theoretical knowledge and practical skills that the rest of the team will use as a reference
guide for their work.
Cell voltages
Oxidation and reduction (REDOX reactions)
Definitions
-oxidation is gain of electrons
-Reduction is loss of electrons
One of the atoms gets oxidation in redox processes, which results in the loss of electrons.
The oxidation state of two species has changed as a result of the reduction of one species
while the reduction of the other. Half equations can be used to show how these reactions
happen. Half equations illustrate the electrolysis process at either the cathode or the anode
electrode.Two different redox half equations occur in an electrochemical cell, with electron
transfer called on by surrounding circuits. The circuit allows for the transfer of electrons, and
the voltmeter reading reflects this energy transfer. The electrode potential is this value.
Part B.P4, B.M4
Standard electrode potential
Hydrogen gas is used as a reference along with a solution of H+ ions to establish the
standard electrode potential, E, which is equal to zero. 1 mol dm-3, 298 K, and 100 kPa are
the standards. A circuit is made by joining the electrodes with wires and the half-cells with a
salt bridge to allow ion movement in order to calculate the standard electrode potential for a
half-cell. The E values demonstrate that larger negative values are more likely to oxidise
(lose electrons). Electrons tend to be added to more positive values (reduction). Two half-
cells are connected to create electrochemical cells, and the voltage is equal to the cell
potential, or E,cell. .
This can be calculated from half-cell potentials as follows:
Eөcell = Eө (cathode) + Eө (anode)
,2021-23 Unit 13 LAB Acid or Base?
Measuring cell potential
Aim
The aim of this investigation is to learn how to build three electrochemical cells so that you
may use a high resistance voltmeter to detect the potential difference between the
electrodes while taking the polarity into account. A positive sign and a negative sign are
displayed on the voltmeter to indicate the polarity of each electrode as the potential
difference between the electrodes for each cell is measured. This would determine the
electrodes at which electrons are produced and at which electrodes they are required.
figuring out the general reaction's progression in that direction.
Equipment
-Copper (II) sulfate solution (0.1M)
- Zinc sulfate solution (0.1M)
- Lead (II) nitrate solution (0.1M
- Strip of copper foil
- Strip of zinc foil
- trip of lead foil
- x3 small emery paper
- Saturated potassium nitrate solution
- Goggles
- x4 50cm3 beakers
- x3 20cm3 measuring cylinders
- X3 leads attached with crocodile clips
- Filter paper strips
- High resistance voltmeter
Risk assessment
Hazards Risks Precautions
Glassware Can break and cause cuts -Glassware should be kept in the
to the skin middle of the table to avoid breaking or
falling off.
-Make sure to work at a clear desk and
stand during the practical
-do not use any cracked/damaged
equipment
Lead (II) nitrate is toxic might be poisonous and Always wear goggles, and cleanse your
irritate the skin and eyes. eyes right away if anything gets in your
eyes and gets in touch with them.
Copper (II) sulfate solution Harmful and can cause Always wear goggles, and cleanse your
irritation to eyes and skin. eyes right away if anything gets in your
eyes and gets in touch with them.
, 2021-23 Unit 13 LAB Acid or Base?
Method
1.Use a different piece of emery paper to scrub each metal strip
2.Each metal strip should be put in its own beaker. Hold each strip vertically so that about 2
cm of it emerges above the rim of the beaker.
3. With a crocodile clip fastened to a lead, fold the edge over the beaker's rim and secure it
in place.
4.Make sure that each metal strip is dipped into a solution of its own ions by adding roughly
20 cm3 of the appropriate salt solution to each beaker. Make sure the crocodile clips aren't
wet.
5.By soaking a strip of filter paper in a saturated potassium nitrate solution, you can create a
salt bridge. Place the strip over the fourth beaker to allow the extra solution to drain off.
6.As illustrated in the diagram below, attach the copper and zinc electrodes to a high
resistance voltmeter, then add the salt bridge to complete the circuit.
7.Reverse the connections to get a positive reading if the voltmeter reading is negative. Note
which electrode is positive (attached to the red terminal of the voltmeter) and which is
negative as you record the potential difference in a results table that is appropriately created.
8.Remove and discard the salt bridge as soon as you can. Cut the voltmeter off.
9.Repeat steps 4 to 7 for the other two cells.
10.Calculate a theoretical value for the potential difference between each cell using the
appropriate standard reduction potential data. Discuss the accuracy and any differences you
notice when comparing the potential differences for the cells that you measured in your
experiment with those that you calculated.
Diagram
(“The Cell Potential”)
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