Factors Affecting Products of Electrolysis are as follows: 1. Products of electrolysis depend on the material being electrolyzed. In other words, the nature of electrolyte governs the process of electrolysis. The process is fast for a strong electrolyte whereas for weak electrolyte an extra potential better known as overpotential is required. Products of electrolysis depend on upon the value of this overpotential too. 2. Products of electrolysis depend on the nature of electrodes too. That is, in the case of the inert electrode (say gold, platinum), it doesnt participate in the reaction whereas if the electrode used is reactive in nature it takes part in the reaction. 3. Various oxidising and reducing species present in the electrolytic cell do affect the products of electrolysis. 4. The products of electrolysis depend on standard electrode potentials of the different oxidizing and reducing species present in the electrolytic cell. 5. In case of multiple reactions, product of electrolysis depends on the standard electrode potential of various reactions taking place. Out of the multiple reduction reactions taking place, the reduction reaction which has highest value of standard electrode potential takes place at cathode. Similarly, out of the multiple oxidation reactions, the oxidation reaction which has the lowest value of standard electrode potential takes place at anode.
Electrolysis of Molten NaCl
If sodium chloride is melted (above 801 C), two electrodes are inserted into the melt, and an electric current is passed through the molten salt, then chemical reactions take place at the electrodes. Since the electrolyte is molten Sodium Chloride we only have Na+ and Cl− ions in the solution. Sodium ions migrate to the cathode, where electrons enter the melt and are reduced to sodium metal: Na++e−→Na Chloride ions migrate the other way, toward the anode. They give up their electrons to the anode and are oxidized to chlorine gas: Cl−→21Cl2+e− The overall reaction is the breakdown of sodium chloride into its elements: 2NaCl→2Na(s)+Cl2(g)
Electrolysis of Aqueous CuBr
When we have an aqueous solution of Copper Bromide we also have to take water into the equation. Since water can be both oxidized and reduced, it competes with the dissolved Cu2+ and Br− ions. So the ions present in the solution are: Br−, Cu2+, H+, OH−. The positive ions are attracted to the negative cathode. There is competition between the copper ions and the hydrogen ions. As the hydrogen ion has lower reduction potential than the copper ion (ERo=+0.521V), the copper ions are preferentially reduced and copper metal is deposited at the electrode (a pink layer is observed) The reaction at Cathode is: Cu2++2e−→Cu(s) The reaction at anode is: 2Br−→Br2(g)+2e− Reduction of Cu2+ (Eo = 0.521 V) is energetically more favorable than the reduction of H2O (Eo = 0 V). So in aqueous solution, reduction of Copper will take place. At the anode, where oxidation occurs, the standard oxidation potential of water is -1.23 volts, while that for bromide ions is -1.07 volts. Hence, Oxidation of Bromine will take place, which is energetically more favorable.
Electrolysis of Aqueous NaCl
When we have an aqueous solution of sodium chloride we also have to take water into the equation. Since water can be both oxidized and reduced, it competes with the dissolved Na+ and Cl− ions. Rather than producing sodium, hydrogen is produced. The reaction at Cathode is: H2O(l)+2e−→H2(g)+2OH− The reaction at anode is: Cl−→21Cl2(g)+1e− Reduction of Na+ (Eo = -2.7 V) is energetically more difficult than the reduction of water (Eo = 0.0 V). So in aqueous solution, reduction of water will take place.