Content Strategy Manager
Cathode and Anode are the two types of electrodes, which act as conductors and help in establishing electrical contact with the non-metallic part of the circuit. These are usually used in electrolytic and galvanic cells. While the Cathode is the positive or oxidizing electrode that takes up electrons from the external circuit, the Anode can be described as the negative or reducing electrode that releases electrons to the external circuit. Let’s discuss cathode and anode in detail along with some important questions.
| Table of Content |
Key Takeaways: Electrodes, Cathode, Anode, Anode sign, Cathode sign, Electrolytic cell, Galvanic cell, Circuit, Electron, external circuit, oxidizing electrode, Electrochemistry
What are Electrodes?
[Click Here for Sample Questions]
- An electrode is an important component of an electrochemical cell that provides a pathway for the conduction of electricity through non-metallic parts of the cell such as the electrolyte.
- It is the conductive part where the transfer of electrons takes place.
- The electrode consists of two main parts: the cathode and anode, which are classified according to the direction of current flow.
Electrodes
Also Read:
What is Cathode?
[Click Here for Sample Questions]
- Cathode is defined as the electrode in which a reduction reaction takes place and gains electrons.
- The polarity of the cathode depends upon the type of cell used.
- In an electrolytic cell, cathodes acquire a negative charge whereas, in a galvanic cell, it acquires a positive charge.
Cathode
Examples of Cathode
- Electrolytic cell: The negative polarity appears at the cathode in an electrolytic cell. The reduction at the cathode is the result of pure metal or hydrogen gas from the metal ions. The one that makes the most reducing species is more cathodic while considering the relative reducing power of the two redox reactions, as compared to the other that itself gets reduced easily.
- Galvanic cell: The cathode which acts as a positive electrode in the galvanic cell, is completely connected to allow the circuit to be completed. The anode of the galvanic cell releases electrons that reach the cell through the circuit wire cathode.
- Electroplating Metal Cathode or Electrolysis: The metal ions from the pure metal surface on the cathode once they are reduced. The material that is required to be plated with pure metal is attached to the cathode and becomes part of the cathode in the solution.
What is Anode?
[Click Here for Sample Questions]
- Anodes are electrodes where oxidation reaction occurs and thus it loses electrons.
- Similar to the cathode, the polarity of the anode depends upon the type of cell.
- Anode acquires a positive charge in an electrolytic cell, and in a galvanic cell, it acquires a negative charge.
- Moreover, an anode can be a plate or wire having an excess positive charge.
Anode
Examples of Anode
- In the galvanic cell or in the discharge battery, the anode acts as a negatively charged terminal as the current flows into the cell through the cathode.
- The current flowing inward will be carried by the electrons that are flowing outwards.
- The negative charge that is flowing in one direction is similar to the positive charge flowing in the opposite direction.
- The anode acts as a positive terminal in a recharging battery and receives the current from the external generator.
- The flow of current within the battery is in the opposite direction as compared to the direction of current during discharge in the recharging battery.
- The anode also acts as a positive terminal wherein the current flows into the device in a diode.
- On the basis of the flow of current which is in the forward direction, the naming of the electrodes of the diode is determined.
- The current enters the tube in vacuum tubes or gas-filled tubes while the anode is the terminal.
Difference Between Cathode and Anode
[Click Here for Sample Questions]
Differences between Cathode and Anode are provided in the table below.
| Cathode | Anode |
|---|---|
| Reduction takes place in a cathode. | Oxidation takes place in an anode. |
| It gains electrons and therefore it is called an Electron acceptor. | It loses electrons and therefore it is called an Electron donor. |
| In an electrolytic cell, it acquires a negative charge. | In an electrolytic cell, it acquires a positive charge. |
| In a galvanic cell, it acquires a positive charge. | In a galvanic cell, it acquires a negative charge. |
| Cathode is the electrode that carries current from the negative terminal to the positive terminal of the battery. | Anode is the electrode that carries current from the positive terminal to the negative terminal of the battery. |
| Cathode attracts cations in an electrolytic cell. | Anode attracts anions in an electrolytic cell. |
Note: Cations and Anions are different from Cathode and Anode. Cations are ions that acquire a positive charge after losing an electron; Anions are ions that acquire a negative charge after gaining an electron.
Experimental Analysis of Electrolytic Cell
[Click Here for Sample Questions]
The experimental analysis of electrolytic and galvanic cells provides better clarity in understanding cathodes and anodes. Consider an electrolytic cell arrangement as given in the figure below:
Here molten sodium chloride is taken as the electrolyte in which Na+ and Cl- ions gets dissociated and are in a free state. A pair of electrodes are immersed into the electrolyte and are connected to a battery.
The electrode connected to the negative terminal of the battery attracts Na+ cations and undergoes a reduction process where electrons are gained and sodium metal is liberated. This forms the cathode.
| Na+ + e- = Na |
The Cl- anions move towards the electrode that is connected to the positive terminal of the battery. It undergoes an oxidation reaction where electrons are lost and Cl2 gas is liberated. This forms the anode.
| 2 Cl- = Cl2 + 2e- |
The electrolysis of molten sodium chloride has decomposed its elements into sodium metal and chlorine gas. Here, the electrons move from the cathode to the anode and therefore we can conclude that the electric current would flow from the anode to the cathode.
Experimental Analysis of Galvanic Cell
[Click Here for Sample Questions]
Galvanic cell or Voltaic cell is an electrochemical cell that works on the principle of spontaneous redox reactions. Consider a galvanic cell set up as shown below:
Experimental Analysis of Galvanic Cell
beakers are taken containing copper sulfate solution and zinc sulfate solution in each.
A salt bridge containing potassium chloride solution is placed between the two beakers to establish electrical contact. Zinc and copper electrodes that act as cathode and anode are immersed in the electrolytes and are connected in a circuit through a switch.
Compared to the electrolytic cell, the polarity of the cathode and anode gets reversed in a galvanic cell.
Here, the electrons from the zinc electrode undergo oxidation and travel via the salt bridge and get reduced at the copper electrode. Thus the electrons move from the zinc electrode (anode) with a negative polarity to the copper electrode (cathode) with a positive polarity.
Electric current always flows in the direction opposite to the flow of electrons.
Things to Remember
- Electrodes are elements that establish electrical contact with a non-metallic medium in a circuit.
- Cathode is an electrode where reduction takes place.
- Anode is an electrode where oxidation takes place.
- Cathode is called an electron acceptor whereas an anode is called an electron donor.
- The polarity of cathode and anode gets reversed in a galvanic cell compared to an electrolytic cell.
Also Read:
Sample Questions
Ques. Write the name of the cell which is generally used in inverters. Write the reactions taking place at the anode and the cathode of this cell. (2 marks)
Ans. The lead storage battery is used in inverters.
At Anode:
Pb(s) + SO4²-(aq) → PbSO4 (s) + 2e-
At Cathode:
PbO2 (s) + SO4²-(aq) → 4H- (aq) + 2e-
Ques. What is corrosion? Explain the electrochemical theory of rusting of iron and write the reactions involved in the rusting of iron. (3 marks)
Ans. Corrosion is defined as the deterioration of a substance because of its reaction to its environment. Corrosion is an electrochemical phenomenon. At a particular spot of an object made of iron, oxidation takes place and that spot behaves as an anode and the reaction is
At Anode : 2Fe → 2Fe²+ + 4e-
Electrons released at an anodic spot move through the metal and go to another spot on the metal and reduce oxygen in presence of H+. This spot behaves as a cathode
At Cathode : O2 + 4H+ + 4e-
Overall reaction : 2Fe + O2 + 4H+ → 2Fe2+ + 2H2O
Ques. What are fuel cells? Explain the electrode reactions involved in the working of the H2 – O2 fuel cells. (3 marks)
Ans. Fuel cells are the devices that convert the energy produced during the combustion of fuels like H2, CH4, etc. directly into electrical energy.
The electrode reaction for H2 – O2 fuel cell:
At anode: 2H2 (g) + 4OH-(aq) → 4H2O (I) + 4e-
At cathode: O2 (g) + 2H2O (I) + 4e- → 4OH-(aq)
Overall reaction: 2H2 (g) + O2 (g) → 2H2O(I)
Ques. Is a cathode positive or negative? (2 marks)
Ans. The cathode is negative. The electrode from which electrons emerge is referred as the cathode and is designated as negative; the electrode that receives electrons can be described as the anode and is designated as positive.
Ques. What are Cathode Rays and Anode Rays? (2 marks)
Ans. Cathode rays consist of material particles which are negatively charged whereas Anode rays consists of material particles which are positively charged.
Ques. What is the difference between Cathode rays and Electrons? (2 marks)
Ans. Cathode rays are rays which emerge from the cathode whereas electrons are subatomic particles which have mass and a negative charge.
Ques. What charge are anode and cathode? (2 marks)
Ans. The anode is negative in a galvanic cell while the cathode is positive. It is because of the fact that anode is the origin of electrons and where the electrons flow is the cathode.
Ques. Write the reactions taking place at the cathode and anode in the lead storage battery when the battery is in use. What happens on charging the battery? (2 marks)
Ans. At Anode: Pb + SO4²-→ PbSO4 + 2e-
at Cathode : PbO2 + SO4²-+ 4H+ + 2e- → PbSO4 + 2H2O
On charging the battery, the reaction is reversed and PbSO4 on the anode and cathode is converted into Pb and PbO2 respectively.
For Latest Updates on Upcoming Board Exams, Click Here: https://t.me/class_10_12_board_updates
Check-Out:
Comments