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Feasibility of Using an Electrolysis Cell for Quantification of the Electrolytic Products of Water from Gravimetric Measurement

Melaku, Samuel, Gebeyehu, Zewdu, Dabke, Rajeev B.
Journal of Analytical Methods in Chemistry (Online) 2018 v.2018
anodes, batteries, carbon dioxide, cathodes, color, electrolysis, gravimetry, hydrogen, ions, neutralization, oxygen, phthalates, potassium bicarbonate, protons, vinegars
A gravimetric method for the quantitative assessment of the products of electrolysis of water is presented. In this approach, the electrolysis cell was directly powered by 9 V batteries. Prior to electrolysis, a known amount of potassium hydrogen phthalate (KHP) was added to the cathode compartment, and an excess amount of KHCO₃ was added to the anode compartment electrolyte. During electrolysis, cathode and anode compartments produced OH⁻(aq) and H⁺(aq) ions, respectively. Electrolytically produced OH⁻(aq) neutralized the KHP, and the completion of this neutralization was detected by a visual indicator color change. Electrolytically produced H⁺(aq) reacted with HCO₃⁻(aq) liberating CO₂(g) from the anode compartment. Concurrent liberation of H₂(g) and O₂(g) at the cathode and anode, respectively, resulted in a decrease in the mass of the cell. Mass of the electrolysis cell was monitored. Liberation of CO₂(g) resulted in a pronounced effect of a decrease in mass. Experimentally determined decrease in mass (53.7 g/Faraday) agreed with that predicted from Faraday’s laws of electrolysis (53.0 g/Faraday). The efficacy of the cell was tested to quantify the acid content in household vinegar samples. Accurate results were obtained for vinegar analysis with a precision better than 5% in most cases. The cell offers the advantages of coulometric method and additionally simplifies the circuitry by eliminating the use of a constant current power source or a coulometer.