Procedure

Materials Required:

• Ammeter
• Voltmeter
• Rheostat
• Beaker
• Reference electrode – Ag/AgCl
• Counter electrode – Pt electrode
• Working electrode – Lead, Zinc, and Silver
• Electrolyte used – Pb(NO₃)₂, ZnSO₄, AgNO₃

Procedure:

1. Choose an electrode.
2. Choose an over potential.
3. Choose a transfer coefficient.
4. Note the current flow from the Ammeter reading.
5. Keeping the transfer coefficient constant, find the current values by varying the over potential.
6. Find the log values corresponding to each current (I).
7. Plot a graph with log I vs η (over potential).
8. From the intercept, log I₀ can be determined. Thus, exchange current density I₀ can be calculated for the particular system.
9. Exchange current densities for different systems can be calculated.

Thus Tafel equation and Tafel Plot is verified.

Working Electrode vs Current Density

Working Electrode	Current Density (A/cm2)
Lead	2.5 × 10−13
Zinc	3 × 10−11
Silver	4 × 10−7

Observations and Calculations:

No	Current Density (A/cm2)	α	n	F (C/mol)	η (V)	R (J/mol·K)	T (K)	I (A)	log I
1			2	96500		8.314	298
2			2	96500		8.314	298
3			2	96500		8.314	298
4			2	96500		8.314	298
5			2	96500		8.314	298
6			2	96500		8.314	298

Results:

1. Tafel equation and Tafel Plot is verified
2. Exchange current, $I_O$ for the particular system =................

Points to Remember while Performing the Experiment in a Real Laboratory:

• Always wear a lab coat and gloves when you are in the lab.
• When you enter the lab, switch on the exhaust fan and ensure that all the chemicals and reagents required for the experiment are available. If not, prepare the reagents using the necessary components.
• Clean all working apparatus with chromic acid and distilled water, and ensure they are free from water droplets before performing the experiment.
• Calibrate the electronic weighing balance before taking measurements.
• Ensure that the ammeter, voltmeter, and rheostat are functioning properly.
• Make sure the calomel electrode contains a sufficient amount of saturated KCl solution.
• Clean all glassware with soap and distilled water.
• Once the experiment is completed, recap all reagent bottles. Switch off the lights and exhaust fan before leaving the lab.
• Discard used gloves in the designated waste bin.