Coulometry is an electroanalytical technique used to determine the concentration of a substance in a solution by measuring the amount of electricity in coulombs required to complete a redox reaction. In the case of determining the amount of chlorine present in a water sample, the following steps can be followed:1. Prepare the sample: Collect a representative water sample and filter it if necessary to remove any suspended particles or impurities that may interfere with the analysis.2. Set up the coulometric cell: The cell typically consists of two electrodes working and counter electrodes and a reference electrode, all immersed in an electrolyte solution. The working electrode is usually made of platinum, while the counter electrode can be made of platinum or another inert material. The reference electrode is typically a saturated calomel electrode SCE or a silver/silver chloride Ag/AgCl electrode.3. Add an appropriate supporting electrolyte: A supporting electrolyte, such as sodium sulfate, is added to the water sample to ensure adequate conductivity and to minimize the ohmic drop between the electrodes.4. Perform the coulometric titration: Apply a constant current between the working and counter electrodes. The current will cause the reduction of chlorine at the working electrode, generating chloride ions. The amount of electricity in coulombs required to completely reduce the chlorine in the sample is directly proportional to the amount of chlorine present.5. Monitor the potential: Measure the potential between the working and reference electrodes during the titration. When all the chlorine has been reduced, the potential will change sharply, indicating the endpoint of the titration.6. Calculate the amount of chlorine: The amount of chlorine in the sample can be calculated using Faraday's law of electrolysis: n = Q / F * z where n is the amount of chlorine in moles, Q is the total charge in coulombs, F is Faraday's constant 96,485 C/mol , and z is the number of electrons transferred in the redox reaction 2 for the reduction of chlorine to chloride ions .7. Convert the amount of chlorine to concentration: Divide the moles of chlorine by the volume of the water sample to obtain the concentration of chlorine in the sample usually expressed in mg/L or ppm .By following these steps, you can accurately determine the amount of chlorine present in a water sample using coulometry.