This document outlines an experiment on electrochemical cells. It describes the objectives of constructing and analyzing galvanic and electrolytic cells. Specifically, it involves determining the cell potential of copper-zinc galvanic cells, observing the effect of concentration on cell potential, performing electrolysis of aqueous potassium iodide to observe electrode reactions, and applying Faraday's law through the electroplating of a coin. Detailed procedures are provided for setting up the galvanic and electrolytic cells, collecting and analyzing products of electrolysis, and measuring changes in mass during electroplating.
Electrochemical Cells and Cell PotentialsObjective The pu.docxtoltonkendal
Electrochemical Cells and Cell Potentials
Objective:
The purpose of this experiment is to create and experiment galvanic cell and collect/interpret data by using a multimeter to describe the flow of electrons. The we g=had to determine how it is calculated by using the formulas given.
Procedure:
Exercise 1: Construction of a Galvanic Cell
1. Gather all of the supplies listed in the materials list. 2. Use the scissors to cut a strip of the filter paper approximately 1.5 inches in width (1/4 the size of the sheet of filter paper). 3. Cut a strip of filter paper and fold the strip of filter paper in half (widthwise) and then in half again. 4. Folding the filter paper in half and then in half again and put on the safety gloves and goggles. 5. Create the salt bridge by carefully winding the folded filter paper into a circle so that it fits into the bottom of the 9 oz. plastic cup. Add the potassium chloride to the cup with the filter paper until the paper is completely covered with the potassium chloride. 6. Folded filter paper in cup. The potassium chloride is added to the cup to cover the filter paper. 7. Allow the paper to soak up the potassium chloride for a minimum of 10 minutes or until you are ready to add it to the galvanic cell, as described later in the experiment. 8. Place the 2 glass beakers on a table. Add approximately 45 ml of zinc sulfate (approximately ½ of the bottle) to one of the beakers. To the second beaker, add approximately 45 ml of copper sulfate. 9. Pick up a fresh strip of zinc and insert 1 end of it into the copper sulfate solution. After approximately 5 seconds, remove the zinc from the copper sulfate and place it on a piece of paper towel.10. Pick up a fresh strip of copper and insert 1 end of it into the zinc sulfate solution. After approximately 5 seconds, remove the copper from the zinc sulfate and place it on the piece of paper towel.11. Metal in solutions. A. Zinc being inserted into copper sulfate. B. Copper being inserted into zinc sulfate and observe the 2 metal strips and record observations in Data Table 1 in your Lab Report Assistant. 12. From the observations, determine which of the 2 reactions is spontaneous. Record this in the observations section of Data Table 1. 13. Set up the voltmeter as follows; a. Make sure the on/off switch of the voltmeter is in the "off" position. b. Place the end of the black probe into the bottom right hole of the voltmeter. c. Place the end of the red probe into the hole directly above the location of the black probe. d. Turn the voltage dial so that the arrow end of the dial is pointing to 20 DCV. e. Add 1 jumper cable clip to each end of the probes. It does not matter what color jumper cable clips are provided in your kit, or which color is attached to either probe. 14. Put the salt bridge into place by submerging 1 end on the copper sulfate and the other end in the zinc sulfate. Adjust the beakers as necessary so that the salt bridge does not sink between the beakers. .
prepared notes as pre Tanzanian syllabus by Mr Saad Miraji a bachelor degree holder in science with education (chemistry and biology) currently teaching at Shamsiye boys secondary school advance chemistry
Potentiometry, Electrochemical cell, construction and working of indicator an...Vandana Devesh Sharma
Potentiometry - Electrochemical cell -Construction and working of reference (Standard hydrogen, silver chloride electrode and calomel electrode)
Indicator electrodes (metal electrodes and glass electrode)
Methods to determine end point of potentiometric titration
and applications
Potentiometry is the method to find the concentration of solute in
A given solution by measuring the potential between two Electrodes
(reference and Indicator electrode) . Potentiometric titration involves
the measurement of the potential of the indicator electrode and
reference electrode.
In potentiometric titration reference and indicator electrodes are
immersed in the solution of particular analyte (titrand) and
potential of indicator electrode is measured with relation to
reference electrode.
Titrant is added in analyte (Titrand) and change in potential is noted
down.
At the end point there is sharp change in potential on indicator
electrode.
Graph is plotted between the indicator electrode potential and
volume of titrant added.
This method is used for determination of sharp end point.
Types of Potentiometric Titration
1. Acid-base titration 2. Redox Titration 3.Complexometric titration 4. Precipitation Titration
Potentiometry: Electrical potential, electrochemical cell, reference electrodes, indicator
electrodes, measurement of potential and Ph, construction and working of electrodes,
Potentiometric titrations, methods of detecting end point, Karl Fischer titration.
2. OBJECTIVES
Upon completion of the experiment, the student be able to:
1. construct and setup galvanic and electrolytic cells;
2. determine the cell potential of galvanic cells;
3. determine the effect of concentration of the cell potential;
4. determine the electrode reactions during the electrolysis of
aqueous solution of potassium iodide and;
5. apply Faraday’s Law on the electroplating of a ten-centavo
coin.
3. LIST OF CHEMICALS
1 M CuSO4
0.001 M CuSO4
aqueous potassium iodide
starch solution
1 M ZnSO4
0.001 M ZnSO4
phenolphthalein
4. LIST OF APPARATUS
voltmeter/ammeter
Cu electrode/strip
salt bridge containing saturated KCI
pipet
dropper
50-mL beakers
Zn electrode/strip
electrolysis setup
test tubes and rack
ten-centavo coins
5. SAFETY PRECAUTIONS
1. Wear laboratory gown or apron during the entire laboratory
period and safety goggles when doing the experiment.
2. All safety rules apply to this experiment.
3. Dispose chemicals on designated bottles.
Notice to Students and Instructors:
Ten-centavo coins should be brought by the students and
must be assigned 1 week prior to the experiment.
6. WASTE DISPOSAL
1. After the experiment, dispose of the solutions in
appropriately-labeled containers in the fume hood.
2. Do not mix different solutions into a single waste
container.
7. Electrochemical Cells- is a device capable of either generating electrical energy from
chemical reactions or facilitating chemical reactions through the introduction of
electrical energy. There are two basic types of electrochemical cells: those
electrochemical devices that generate electricity from spontaneous reactions are
known as galvanic cells (aka voltaic cells), while those that make use of electricity or
electric current for certain chemical reactions to occur are termed electrolytic cells.
Galvanic Cell- is an electrochemical cell that derives electrical energy from
spontaneous redox reactions taking place within the cell.
Electromotive force (emf)- is the voltage developed by any source of electrical
energy such as a battery or dynamo.
8. Electrolytic Cell- is an electrochemical cell that undergoes a redox reaction when
electrical energy is applied. A common example of an electrochemical cell is
a standard 1.5-volt "battery". (Actually a single "Galvanic cell"; a battery
properly consists of multiple cells, connected in either parallel or series
pattern.)
Electrolytic Cell- is an electrochemical cell that undergoes a redox reaction when
electrical energy is applied. A common example of an electrochemical cell is
a standard 1.5-volt "battery". (Actually a single "Galvanic cell"; a battery
properly consists of multiple cells, connected in either parallel or series
pattern.)
Electroplanting- is a process that uses electrical current to reduce dissolved
metal cations so that they form a coherent metal coating on an electrode.
Electroplating is primarily used to change the surface properties of an object
(e.g. abrasion and wear resistance, corrosion protection, lubricity, aesthetic
qualities, etc.), but may also be used to build up thickness on undersized
parts or to form objects by electroforming.
9. PROCEDURE
I. VOLTAGE DETERMINATION
A. Construction of a Galvanic
1. Place 25.0 mL each of 1M CuSO4 solutions in two
separate 50-mL beakers.
2. Dip a copper (Cu) electrode in the CuSO4 solution and a
zinc (Zn) electrode into the ZnSO4 solution.
3. Connect the two solutions by a salt bridge containing
saturated KCI. (Ensure that each end of the salt bridge is
immersed into each of the solutions.)
4. Connect the Zn electrode to the negative terminal of the
voltmeter and the Cu electrode to the positive terminal.
5. Allow the cell to stand for 3 minutes and read the cell
potential as well as the temperature of the solutions.
10. B. Effect of Concentration on the Cell Voltage
Repeat the procedure describe above, this time using the following
Pairs of solutions:
1. 1M ZnSO4 and 0.001M CuSO4
2. 0.001M ZnSO4 and 1M CuSO4
11. II. ELECTROLYSIS OF AQUEOUS POTASSIUM IODIDE
A. Electrolytic Cell Set Up
1. Set up the electrolytic apparatus shown in Figure 5.3 using aqueous potassium
iodide as your electrolyte.
2. Use only enough electrolyte solution to fill the tube just above the bridge
connecting the two test tubes.
3. Mark the electrodes as X and Y.
4. Connect electrode X to the negative terminal of the battery and electrode Y to the
positive terminal.
5. Complete the circuit and allow electrolysis to proceed.
12. B. Electrolysis of Aqueous Potassium Iodide
1. Break the current after visible changes are observed.
2. Carefully remove the electrodes.
3. Simultaneously draw out about 2 mL of the solution at each electrode and place
into two marked test tubes.
4. Draw out another set of 2 mL solutions at each electrode and label them properly.
5. To the first pair of liquids drawn out, add 2 mL of starch solution to each test tube
and shake for about a minute. (Molecular iodine (I2) forms a complex with starch
producing a blue solution.)
6. To the second set of solutions drawn, add 3 drops of phenolphthalein to each of the
test tube. Observe any color change.
13. III. FARADAY’S LAW AND ELECTROPLATING
1. Polish a ten-centavo coin and a strip of copper properly.
2. Measure the mass of the coin and the copper using a top loading balance.
3. Prepare 30 mL of 1.0 CuSO4 solution in a 50-mL beaker.
4. Set up the apparatus and ensure that the copper strip is connected to the positive
terminal (anode) and the coin to the negative terminal (cathode) of the 6V battery.
5. Start timing the electrolysis once the coin and copper strip is immersed and the
circuit is complete.
6. Allow for electrolysis to proceed for 15 minutes. Record the amperage every 3
minutes.
7. Remove the copper strip and the coin after 15 minutes and allow these to air dry.
8. Measure the mass of the coin and the copper strip when completely dry.