How to Determine Products of Electrolysis in Aqueous and Molten Electrolytes
The electrochemical cell that facilitates a chemical reaction via the induction of electrical energy is called an electrolytic cell. The process of carrying out non-spontaneous reactions under the influence of electrical energy is called electrolysis. Electrolysis is commercially essential as a stage for the separation of elements from the naturally occurring substances such as the ores with the help of an electrolytic cell. The voltage which is needed for the electrolysis to occur is known as the decomposition potential. In this article, we will learn about electrolysis, mechanism of electrolysis, and the process of electrolysis. Let us first learn about the electrolysis process in detail.
What is Electrolysis?
Electrolysis is a process by which the electric current is passed through a substance which effects sort of a chemical change. This chemical change is the one in which the substance loses or gains an electron, which means, it undergoes oxidation or reduction. This process is carried out in an electrolytic cell, which is an apparatus that consists of the positive and the negative electrodes held apart and are dipped into a solution containing the positively and the negatively charged ions.
The substance that is to be transformed might form the electrode, might constitute the solution or might be dissolved in the solution. Electric current, that is, the electrons enters through the negatively charged electrode or the cathode. The components of the solution travel to this electrode, combine with the electrons and are transformed or reduced. The products that are obtained can either be neutral elements or new molecules.
The components of the solution also travel to the other electrode, which is the anode, give up their electrons, and are transformed or oxidized to the neutral elements or new molecules. If the substance to be transformed is the electrode, then the reaction is often the one in which the electrode dissolves by giving up the electrons.
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Factors Affecting the Product of Electrolysis
Given below are the factors affecting the product of electrolysis.
The products of electrolysis depend on the material that is being electrolyzed. In simpler words, the nature of electrolyte decides the process of electrolysis. This process is fast for a strong electrolyte whereas for a weaker electrolyte an extra potential, otherwise known as overpotential, is required. Products of electrolysis depend on the value of this overpotential too.
The products of electrolysis depend upon the nature of electrodes as well. This means that, in the case of the inert electrode (for example, gold, and platinum), it does not participate in the reaction, whereas, in case the electrode that is used is reactive in nature, it takes part in the reaction.
Several oxidising and reducing agents present in the electrolytic cell affect the products of electrolysis.
The products of electrolysis depend on the standard electrode potentials of the different oxidizing and reducing agents that are present in the electrolytic cell.
In case there are multiple reactions, the product of electrolysis depends upon the standard electrode potential of several reactions that are taking place. For example, the electrolysis of an aqueous solution of sodium chloride. Out of the several multiple reduction reactions that are taking place, the reduction reaction that has the highest value of the standard electrode potential takes place at the cathode. Similarly, out of the several oxidation reactions, the oxidation reaction that has the lowest value of the standard electrode potential takes place at the anode.
Inert Electrode
Let us now learn about what is an inert electrode.
An inert electrode is an electrode which serves only as a source or sink for the electrons without taking part as a chemical role in the electrode reaction. Precious metals, mercury, and carbon are some of the elements that are generally used as inert electrodes. The inert nature of the electrode can often be questioned. However, the electrode may not take part in the reaction in the form of a reactant or a product but can still act as an electrocatalyst.
FAQs on Electrolysis Products at Anode and Cathode Explained
1. What are the products of electrolysis?
The products of electrolysis are substances formed at the anode (oxidation) and cathode (reduction) when electricity passes through an electrolyte.
- At the cathode: Reduction occurs (gain of electrons).
- At the anode: Oxidation occurs (loss of electrons).
- The actual products depend on the type of electrolyte (molten or aqueous) and the ions present.
2. What are the products of electrolysis of water?
The electrolysis of water produces hydrogen gas at the cathode and oxygen gas at the anode.
- Overall balanced equation: 2H2O(l) → 2H2(g) + O2(g)
- Cathode reaction: 2H2O(l) + 2e- → H2(g) + 2OH-(aq)
- Anode reaction: 4OH-(aq) → O2(g) + 2H2O(l) + 4e-
3. What are the products of electrolysis of molten sodium chloride?
The electrolysis of molten sodium chloride (NaCl) produces sodium metal and chlorine gas.
- Cathode: Na+(l) + e- → Na(l)
- Anode: 2Cl-(l) → Cl2(g) + 2e-
- Overall reaction: 2NaCl(l) → 2Na(l) + Cl2(g)
4. What are the products of electrolysis of aqueous sodium chloride?
The electrolysis of aqueous sodium chloride (brine) produces hydrogen gas, chlorine gas, and sodium hydroxide solution.
- Cathode: 2H2O(l) + 2e- → H2(g) + 2OH-(aq)
- Anode: 2Cl-(aq) → Cl2(g) + 2e-
- Overall reaction: 2NaCl(aq) + 2H2O(l) → H2(g) + Cl2(g) + 2NaOH(aq)
5. How do you predict the products of electrolysis?
To predict the products of electrolysis, identify which ions are discharged at the cathode and anode based on their reactivity and electrode potentials.
- Step 1: List all ions present in the electrolyte.
- Step 2: At the cathode, the less reactive metal or hydrogen is reduced.
- Step 3: At the anode, halide ions (Cl-, Br-, I-) are oxidized preferentially; otherwise oxygen forms from water or OH-.
- Step 4: Write balanced half-equations and the overall equation.
6. Why are different products formed in molten and aqueous electrolysis?
Different products form because water participates in aqueous electrolysis but is absent in molten electrolysis.
- In molten electrolytes, only the compound’s ions are present.
- In aqueous solutions, water can be reduced to H2 or oxidized to O2.
- This changes which species is preferentially discharged at each electrode.
7. What is formed at the cathode during electrolysis?
The cathode is where reduction occurs and a metal or hydrogen gas is formed.
- Metal cations gain electrons: Cu2+(aq) + 2e- → Cu(s)
- In aqueous solutions, hydrogen may form: 2H2O(l) + 2e- → H2(g) + 2OH-(aq)
8. What is formed at the anode during electrolysis?
The anode is where oxidation occurs and a non-metal such as oxygen or a halogen is produced.
- Halide example: 2Cl-(aq) → Cl2(g) + 2e-
- Oxygen example: 4OH-(aq) → O2(g) + 2H2O(l) + 4e-
9. What are the products of electrolysis of copper(II) sulfate solution?
The products of electrolysis of aqueous copper(II) sulfate depend on the electrode type.
- With inert electrodes:
- Cathode: Cu2+(aq) + 2e- → Cu(s)
- Anode: 4OH-(aq) → O2(g) + 2H2O(l) + 4e-
- With copper electrodes: Copper dissolves at the anode: Cu(s) → Cu2+(aq) + 2e-
10. What factors affect the products of electrolysis?
The products of electrolysis are affected by the electrolyte type, ion concentration, and electrode material.
- Nature of electrolyte (molten vs aqueous)
- Relative reactivity or standard electrode potentials
- Concentration of ions (e.g., concentrated vs dilute NaCl)
- Type of electrode (inert like Pt/graphite or reactive like Cu)
