Question

Why do anions move towards anode and cations move towards cathode in electrolysis?

Short answer

Answer: Anions move towards the anode and cations move towards the cathode during electrolysis due to the electric field created by the applied voltage, which causes the charged ions to experience a force in their respective directions. Additionally, the fundamental principle of electrostatics - that opposite charges attract each other - also contributes to this movement. When these ions reach their respective electrodes, they undergo redox reactions resulting in new species or the deposition of elements.

Step-by-step solution

1. Understanding Electrolysis

Electrolysis is a process in which electrical energy is used to drive a non-spontaneous chemical reaction, resulting in the separation of ions present in a solution or molten compound. During electrolysis, a direct current is passed through the electrolyte, causing the flow of electrons from one electrode to another.

2. Components of an Electrolytic cell

An electrolytic cell consists of two electrodes (the anode and the cathode) and an electrolyte containing ions that can conduct electricity. The anode is the positive electrode connected to the positive side of the power source, while the cathode is the negative electrode connected to the negative side of the power source.

3. Electric Field and Movement of Ions

An electric field is produced between the anode and the cathode when a voltage is applied across the electrodes. The negatively charged anions experience a force in the direction of the electric field, causing them to move towards the positive electrode (anode). On the other hand, the positively charged cations experience a force in the opposite direction of the electric field, causing them to move towards the negative electrode (cathode).

4. Attraction and Repulsion between Charges

The fundamental principle of electrostatics states that "opposite charges attract and like charges repel each other." In the case of electrolysis, positively charged cations are attracted to the negatively charged cathode, and negatively charged anions are attracted to the positively charged anode. Due to this principle, cations move towards the cathode and anions move towards the anode.

5. Redox Reactions at Electrodes

Once the charged ions reach their respective electrodes, they undergo oxidation or reduction, resulting in the formation of new species or deposition of elements. At the anode, anions lose electrons (oxidation) and form neutral atoms or molecules. At the cathode, cations gain electrons (reduction) and form neutral atoms or molecules. This process results in the transfer of electrons, completing the circuit and allowing the flow of current through the electrolytic cell. In conclusion, anions move towards the anode, and cations move towards the cathode during electrolysis due to the influence of the electric field created by the applied voltage and the fundamental principle that opposite charges attract each other. Once reaching their respective electrodes, the ions undergo redox reactions resulting in new species or the deposition of elements.