How to Figure out the Products Formed at the Electrodes on Electrolysis – Part 1

Electromotive force (EMF) or electromotance is an energy transfer to an electric circuit per unit of electric charge.


An electrochemical cell is a device that either generates electrical energy from chemical reactions in a so-called galvanic or voltaic cell, or induces chemical reactions (electrolysis) by applying external electrical energy in an electrolytic cell.

Redox potential aka oxidation/reduction potential (ORP or Ered) is a measure of the tendency of a chemical species to gain electrons from or lose electrons to an electrode; and therefore, be reduced or oxidized respectively.

As per the IUPAC (international union of pure and applied chemistry), standard electrode potential (EѲ) is the value of the standard emf (electromotive force) of a cell in which molecular hydrogen under standard pressure is oxidized to solvated protons at the left-hand electrode.

Mnemonics: OIL RIG (Oxidation Is Loss, Reduction Is Gain)

An Ox, Red Cat (Anode Oxidation, Reduction Cathode)

Question:



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Solution:



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Brine = Aq. Sodium chloride (NaCl) conc. soln.

Overall cell rxn: 2NaCl(aq) + 2H2O(l) → H2(g) + Cl2(g) + 2NaOH(aq)

The chloralkali process is a large-scale application of electrolysis of brine that supplies most of the Chlorine gas and Sodium hydroxide required by many industries.

Na(s) is not formed because it is too reactive and would instantly react with water.

H2O Ox => Local acidity ↑

Enigmatic electrolysis❓ Let Chemaficionado know in the comments below or at mychemistryhomework@gmail.com❗

References:

‌(1)    Ncert. Chemistry : Textbook for Class XII - Part.I; National Council Of Educational Research And Training: New Delhi.

(2)    Brown, C.; Ford, M. Higher Level Chemistry, 2nd ed.; Pearson Education: Harlow, Essex, 2014.

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