3B Scientific Electrochemistry Kit User Manual
3B SCIENTIFIC® PHYSICS
... going one step further
ELECTROCHEMISTRY
U11110
ALF 05/04
Practical experiments
for secondary levels I and II
Contents
Preface 4
Contents of the Electrochemistry case 5
Assembly and cleaning of the battery block 6
Description of the meter 7
Measuring the voltage of galvanic cells - teacher's instructions 8
Measuring the voltage of galvanic cells - student instructions 9
Measuring the voltage of a Daniell cell - teacher's instructions 10
Measuring the voltage of a Daniell cell - student instructions 11
Measuring the voltage of three Daniell cells connected in parallel - teacher's instructions 12
Measuring the voltage of three Daniell cells connected in parallel - student instructions 13
Measuring the voltage of three Daniell cells connected in series - teacher's instructions 14
Measuring the voltage of three Daniell cells connected in series - student instructions 15
Measuring the standard electrochemical potential of various metals - tea cher's instructions 16
Measuring the standard electrochemical potential of various metals - student in structions 17
Measuring the standard electrochemical potential of various non-metals - teacher's in structions 18
Measuring the standard electrochemical potential of various non-metals - student instructions 19
Measuring the voltage of a zinc-carbon (Leclanché) cell - teacher's instructions 20
Measuring the voltage of a zinc-carbon (Leclanché) cell - student instructions 21
Measuring the voltage for various electrolyte concentrations - teacher's instru ctions 22
Measuring the voltage for various electrolyte concentrations - student instructio ns 23
Measuring the voltage for various electrolyte temperatures - teacher's instructions 24
Measuring the voltage for various electrolyte temperatures - student instructions 25
Design, charging and discharging of a steel accumulator - teacher's instructions 26
Design, charging and discharging of a steel accumulator - student instructions 27
Experiment - measuring pH - teacher's instructions 28
Experiment - measuring pH - student instructions 29
Standard electrochemical potential series 30
Notes on performing experiments and disposing of materials 31
Bibliography 32
3
Page
Preface
The electrochemistry case is a teaching aid exclusively designed for chemistry and physics
experiments in schools.
The fact that students can perform experiments themselves deepens their understanding of the
subjects being treated. The experiments should be performed in small groups of not more than two
or three students. Thus the teacher is only required to supervise and may also give suitable advice
on specific questions that students are unable to answer themselves. Careful organization of
workgroups can therefore add to the achievement, understanding and enjoyment of all students.
The accompanying literature reduces to a minimum the teacher's preparation time, which may for
school experiments in particular be quite lengthy. With each experiment there are instructions for
both teacher and students. The teacher's instructions include descriptions of all the facts required
for the conduct of the experiment. The expected results for each experiment can be found in the
teacher's instructions. (These may differ slightly from the theoretical results given in text books.)
The teacher is also given instructions on how to prepare suitable electrolyte solutions.
The student instructions can be copied by the teacher and distributed to the students. This means
that there is no need to go to the extra lengths of writing down an experiment procedure, freeing
the student to concentrate on the essentials of the experiments themselves.
To ensure safety, German R (Risk) and S (Safety) phrases and hazard symbols are included for all
chemicals used.
At the end of the instructions, notes can be found on the disposal of chemicals. In order to prevent
wastage on chemicals, we recommend that once an experiment is finished, the electrolyte
solutions that have been used should be removed from the chambers of the trough using the
supplied pipette and stored in a labelled container for use in subsequent experiments. This also
makes a contribution to the environment.
We would be grateful for comments and modifications (or notification of any errors) pertaining to
the experiments. Please contact your supplier for the Electrochemistry case.
We wish you success in carrying out the experiments.
4
Contents of the Electrochemistry case
1 Meter for electrochemical and pH experiments,
powered by battery or mains power supply.
1 3V adapter for electrolyzing platinum gauze electrode
1 Mains power supply prim:
115..240VAC
,
1 Combined probe for measuring pH, electrode in storage vessel
2 Plastic beakers 25 ml
2 Pipettes
1 Storage box with:
2 silver electrodes, 4 zinc electrodes, 2 iron electrodes, 2 carbon electrodes,
2 aluminum electrodes, 2 nickel electrodes, 4 copper electrodes, 1 magnesium electrode
(magnesium strip to wrap around a plastic plate), 1 platinum gauze electrode
2 half cells for 4 electrodes each, 1 set of filter paper strips,
1 set of cables for electrochemistry (consisting of: 3 cables with crocodile clips, red,
each 20 cm long,
1 cable with crocodile clip and plug, red, 30 cm long, 3 cables with crocodile clips, blue,
each 20 cm long, 1 cable with crocodile clip and plug, blue, 30 cm long),
1 emery stone
1 set of instructions for experiments
50-60Hz
5
sec:
12V–500mA
Assembly and cleaning of the battery block
The battery block is supplied fully assembled and can be used for experiments immediately. It is
stored in the storage box inside the case.
If the battery block is used, it must be disassembled after the experiment is finished by undoing the
knurled screws to completely separate the two half cells so that the electrolyte can be sucked out
and the electrolytes removed. After removing the filter paper, the two half cells should be rinsed out
with water and then thoroughly dried.
Reassemble the battery block for use in subsequent experiments. This involves placing one of the
supplied filter paper strips flush between the two half cells. When this is done, first one and then
the second knurled screw should be poked through the filter paper and the two half cells should
then be screwed firmly together. (Note: The four openings on the inside must all face the filter
paper (as in the illustration).
The 8 chambers are electrically connected via the filter paper, which becomes wet when the
chambers are filled with electrolyte.
Please take care:
After the set is used, all the components employed must be thoroughly cleaned and dried.
Remove the filter paper between the battery blocks and dry both the knurled screws.
The electrodes used should be cleaned under running water and dried in order to avoid corrosion.
It is recommended that the electrodes be rubbed with the emery stone after use in order to
thoroughly remove any chemical residues that may have been deposited.
If you follow these instructions, you should get plenty of enjoyment from your case.
6
Meter
Front
Range display/
battery charge
――――――>
Off/range switch ―――――>
Terminal sockets ―――――>
<―――――― LCD display
<― Zero point adjuster (for pH )
Rear
Mains power supply socket ―>
<――――――― pH socket
Brief instructions for
voltage measureme
nts ―――>
Brief instructions for
<―
pH measurement
The meter is battery powered but can also be used with the power supply unit provided. The battery is
recharged completely when the device is used with the power supply and overcharging is impossible. The
power supply is plugged in to the bottom of the instrument.
In addition to voltage measurement, pH can also be measured with the meter.
1. Voltage measurement
To perform voltage measurement, the meter is turned on via the range switch and is then initially configured
for the range 0 - 2V. If higher voltages are to be measured, the instrument can be reconfigured for 20 V by
using the range switch again. Electrodes are connected to the meter via 2 mm sockets (red/blue) in order to
take measurements.
2. pH measurement
If pH is to be measured, the supplied combined pH electrode is connected to the pH socket at the bottom.
Set the range switch to “pH”. To calibrate the combined pH electrode, a buffer solution is employed (either
pH 4 or pH 9). This is a single-point calibration. After the pH electrode is immersed in the relevant buffer
solution, the zero point adjuster is altered until the displayed pH value matches that of the buffer solution. It
is now possible to conduct pH measurements. However, no further changes should be made to the
adjustment knobs.
7
Experiment 1 - Measuring voltage
Measuring the voltage of galvanic cells - teacher's instructions
Chemicals Hazard
R phrases S phrases Equipment
Teacher's instructions
symbols
Copper (II)-sulfate-(5 H2O)
Zinc sulfate-(7H2O)
Silver nitrate
Iron (II)-sulfate-(7 H2O)
Nickel sulfate-(6H2O)
Distilled water --- ---
Warning:
Please take care:
Salts of heavy metals are poisonous!
22-36/38-50/53 22-60-61 Meter
36/38-50/53 22-25-60-61 Electrodes:
34-50/53 26-45-60-61 2 Experiment cables
22-36/38 24/25 2 Pipettes
22-40-42/43-
50/53
22-36/37-60-
61
1 Cu, 1 Zn,1 Ag, 1 Fe, 1 Ni
Experiment procedure:
1. The prepared 1.0 and 0.1 molar electrolyte solutions should be given to the students. Students require no more than
10 ml of the relevant solution each.
2. Assemble the battery block as described.
3. Fill the chambers with electrolyte using the pipette (included in the case) and insert the appropriate electrodes.
Clean the pipette thoroughly before using it add the next electrolyte.
4. After the chambers (at least 2, at most 8) have been prepared for the experiment as described, start measuring
voltages. In this experiment, each of 5 chambers is filled with a separate electrolyte and
the corresponding electrode is inserted to make up a galvanic cell:
Cu / CuSO
, Zn / ZnSO4 , Ag / AgNO3 , Fe / FeSO4 , Ni / NiSO4
4
5. To measure voltage, two experiment cables (red/blue with 2mm plugs - included in case) should be connected to the
voltmeter. The connection between the two electrodes and the meter is made by means of crocodile clips.
6. The voltage produced by the galvanic cell can be read off the meter. If a negative voltage is displayed, reverse the
polarity of the two electrodes.
Observation and evaluation:
In galvanic cells, the less electropositive metal always forms the negative pole.
Electrons always flow from negative to positive poles, i.e. for a zinc/copper combination, they flow from the zinc to the copper and in a
copper/silver combination, they flow from copper to silver.
The combinations involving zinc always have zinc as the negative pole and those involving silver always have silver as the positive pole
of the galvanic element. An electrochemical potential series for these metals thus has the following order:
Zn
Which of the electrodes forms the negative pole can be determined by reversing the polarity.
Galvanic cell Voltage (V)
Cu / Zn
Cu / Ag
Cu / Fe
Cu / Ni
Zn / Ag
Zn / Fe
Zn / Ni
Fe / Ag
Fe / Ni
Calculation of masses required to prepare a 0.1 molar solution:
The electrolyte solutions should be made up by the teacher in sufficient quantities (usually 1 liter suffices) in advance of the lesson.
1.
1 liter of 1.0 molar CuSO
2.
1 liter of 1.0 molar ZnSO
3. 1 liter of 1.0 molar AgNO
4. 1 liter of 1.0 molar FeSO
5.
1 liter of 1.0 molar NiSO4 solution: Add water to 262.70 g NiSO4 (6 H2O) up to 1 liter in a measuring flask.
To make up a 0.1 molar solution, simply use 1/10 of the quantities given above (for making a 1.0 molar solution)
and add water up to 1 liter in a measuring flask.
Ag / Ni
solution: Add water to 249.50 g CuSO4 (5 H2O) up to 1 liter in a measuring flask.
4
solution: Add water to 287.40 g ZnSO4 (7 H2O) up to 1 liter in a measuring flask.
4
solution: Add water to 169.88 g AgNO3 up to 1 liter in a measuring flask.
3
solution: Add water to 277.90 g FeSO4 (7 H2O) up to 1 liter in a measuring flask.
4
→
Fe → Ni → Cu → Ag
Electrolyte 1.0 mol/l
1.086 approx. 1.086 approx.
0.383 approx. 0.383 approx.
0.670 approx. 0.670 approx.
0.044 approx. 0.044 approx.
1.416 approx. 1.416 approx.
0.378 approx. 0.378 approx.
1.095 approx. 1.095 approx.
1.089 approx. 1.089 approx.
0.700 approx. 0.700 approx.
0.290 approx. 0.290 approx.
Electrolyte 0.1 mol/l
Voltage (V)
8
Experiment 1 - Measuring voltage Student instructions
Measuring the voltage of galvanic cells
Chemicals Hazard
symbols
Copper (II)-sulfate-(5 H2O)
Zinc sulfate-(7H
Silver nitrate
Iron (II)-sulfate-(7 H
2
O)
2
O)
Nickel sulfate-(6H
Distilled water
2
O)
R phrases S phrases Equipment
22-36/38-50/53 22-60-61 Meter
36/38-50/53 22-25-60-61 Electrodes:
34-50/53 26-45-60-61 2 Experiment cables
22-36/38 24/25 2 Pipettes
22-40-42/43-
50/53
---
22-36/37-60-
61
---
1 Cu, 1 Zn,1 Ag, 1 Fe, 1 Ni
Warning:
Please take care:
Experiment procedure:
1. The prepared 1.0 and 0.1 molar electrolyte solutions should be given to the students. Students require no more than
10 ml of the relevant solution each.
2. Assemble the battery block as described.
3. Fill the chambers with electrolyte using the pipette (included in the case) and insert the appropriate electrodes.
Clean the pipette thoroughly before using it add the next electrolyte.
4. After the chambers (at least 2, at most 8) have been prepared for the experiment as described, start measuring
voltages.
In this experiment, each of 5 chambers is filled with a separate electrolyte and
the relevant electrodes are added to form a galvanic cell
Cu / CuSO
5. To measure voltage, two experiment cables (red/blue with 2mm plugs - included in case) should be connected to the
voltmeter. The connection between the two electrodes and the meter is made by means of crocodile clips.
6. The voltage produced by the galvanic cell can be read off the meter. If a negative voltage is displayed, reverse the
polarity of the two electrodes.
Observation and evaluation:
Enter the results of the experiment in the following table and evaluate them.
Galvanic cell Voltage (V)
Cu / Zn
Cu / Ag
Cu / Fe
Cu / Ni
Zn / Ag
Zn / Fe
Zn / Ni
Fe / Ag
Fe / Ni
Ag / Ni
Salts of heavy metals are poisonous!
, Zn / ZnSO4 , Ag / AgNO3 , Fe / FeSO4 , Ni / NiSO4
4
Electrolyte 1.0 mol/l
9
Voltage (V)
Electrolyte 0.1 mol/l
Experiment 2 - Measuring voltage Teacher's instructions
Measuring the voltage of a Daniell cell
Chemicals Hazard
symbols
Copper (II)-sulfate-(5 H
Zinc sulfate-(7H
Distilled water
2
O)
2
O)
R phrases S phrases Equipment
22-36/38-50/53 22-60-61 Electrodes:
36/38-50/53 22-25-60-61 2 Experiment cables
--- --- 2 Pipettes
Meter
1 Cu, 1 Zn
Warning:
Please take care:
Salts of heavy metals are poisonous!
Experiment procedure:
1. The prepared 0.1 molar electrolyte solutions should be given to the studen ts. Students require no more than 10 ml of
the relevant solution each.
2. Assemble the battery block as described.
3. Fill one chamber each with electrolyte using the pipette (included in the case). Clean the pipette thoroughly before
using it add the next electrolyte.
4. Insert the appropriate electrodes into the electrolyte solutions, CuSO
5. After the chambers have been prepared for the experiment as described, connect the experiment cable s to the
meter and start measuring voltages. If a negative voltage is displayed, reverse the polarity of the two electrode
connections.
6. The experiment can also be repeated using 1.0 molar copper sulfate and zinc sulfate solutions.
Observation and evaluation:
/ Cu and ZnSO4 / Zn.
4
Sketch of experiment set-up:
+ +
Meter
Cu
-
Zn
The electrolyte solutions should be made up by the teacher in sufficient quantities (usually 1 liter suffices) in advance of the lesson.
Calculation of masses required to prepare a 0.1 molar solution:
1.
1 liter of 0.1 molar CuSO4 solution: Add water to 24.95 g CuSO4 (5 H2O) up to 1 liter in a measuring flask.
2.
1 liter of 0.1 molar ZnSO4 solution: Add water to 28.74 g ZnSO4 (7 H2O) up to 1 liter in a measuring flask.
Calculation of masses required to prepare a 1.0 molar solution:
1. 1 liter of 1.0 molar CuSO
2. 1 liter of 1.0 molar ZnSO
solution: Add water to 249.50 g CuSO4 (5 H2O) up to 1 liter in a measuring flask.
4
solution: Add water to 287.40 g ZnSO4 (7 H2O) up to 1 liter in a measuring flask.
4
When the meter is connected to the Daniell cell with Cu / CuSO4 or Zn / ZnSO
an electrolyte concentration of 0.1 mol/l. The result of the actual measurement is usually slightly less than the theoretical value at
1.06 V.
If a 1.0 molar solution is used in the Daniell cell, the measured voltage should still be 1.06 V.
the measured voltage should theoretically be 1.08 V for
4
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