What Is the Difference Between Cathode and Anode in Electrochemical and Electrolytic Cells
In electrochemical cells, semiconductor diodes and in some medical devices, electrodes are used as a conductor which conducts electricity from non-metallic parts of the circuits. In other words, we can say that an electrode is a substance which conducts electricity in the electric current, which either enters or leaves the non-metallic medium like an electrolyte. Anode and cathode are the two types of electrodes. An anode is an electrode from which polarized current enters the outer circuit, and a cathode is an electrode from which a conventional current leaves a polarized electrical device. The anode and cathode charge are positive and negative respectively. The anode cathode symbol respectively are A and K.
The word anode originates from the Greek word anodes which means way up, and the word cathode originates from another Greek word, cathodes which means way down.
Electrochemical Cell
What is Anode and Cathode?
Anode and cathode are electrodes used in an electrolytic cell and electrochemical cell. Anode and cathode sign are positive and negative. A and K are the respective symbols of anode and cathode. The details of anode and cathode are given below.
Anode
Generally, the anode is the electrode where oxidation reaction takes place, which means at the anode, electrons are getting released into the external circuit. In the electrolytic cell, the anode is a positive electrode, and in the galvanic cell, the anode is a negative one. the sign of anode is ‘+’
In an electrolytic cell, which uses electrical energy for the propagation of a chemical reaction, In galvanic cells or electrochemical cells, which produce electrical energy by a chemical reaction, the anode is negative since it has a negative potential compared to the solution. The anode of a galvanic cell is zinc metal which is dipped in ZnSO4 solution. The Zn metal oxides to Zn2+ and gives two electrons into the external circuit.
Cathode
Generally, the cathode is the electrode where reduction reaction takes place. This means the cathode gains electrons from the external circuit and gets reduced. The sign of cathode is ‘-’.
In galvanic cells, copper is a cathode which is dipped in CuSO4 solution. Cu2+ ions accept electrons from the external cell and are reduced to Cu metal and deposited on the cathode.
There are two types of cathodes, hot cathode and cold cathode. Cold cathodes are cathodes that are not electrically heated by a filament. Which emits more electrons than can be supplied by thermionic emission. Hot cathodes are heated by electric current passing through the filament. The cold cathode is used in discharge lamps, discharge tubes, and in some vacuum tubes.
Anode and Cathode in Electrolysis
During electrolysis a chemical reaction or change takes place by the passage of electricity through the circuit and an electrolytic cell is the device which converts electrical energy to chemical energy. The charge of anion and cation is positive and negative respectively in an electrolytic cell. Consider the electrolysis of molten NaCl.
The anode of the wire or plate is having excessive positive charge because it is connected to the positive terminal of the battery. Hence anions will tend to move towards the anode and give off the electrons to the anode and get oxidized. These electrons are given by anion pass to the external circuit. In the electrolysis of molten NaCl, two inert electrodes are dipped in molten NaCl solution. When the electricity passes, the anode develops an excess positive charge and Cl- ions from the solution move towards the anode, where they become oxidized to sodium metal.
The cathode connects to the negative terminal of the battery, and it contains an excess negative charge. Cations from the solution move towards it and get reduced by accepting the electrons from the external circuit. Conversely, in galvanic cells, the cation is a positive electrode. When molten NaCl is subjected to electrolysis when electricity is passed, Na+ Ions start moving towards the cathode, where it is reduced to become sodium metal.
Difference Between Anode and Cathode
Key Features
Anode and cathode are electrodes used to make electrolytic and electrochemical cells.
Anode is the electrode where oxidation reaction takes place, and in the cathode, reduction takes place.
Anode is the electrode where electricity moves into the external circuit, and cathode is the electrode where electricity is given out.
the charge of anode and cathode are positive and negative in an electrolytic cell and in the galvanic cell it is the opposite
Conclusion
Anode is the positive part of electrolyte where oxidation takes place and cathode is the negative part of the cell where reduction takes place. The symbol of anode and cathode are A and K respectively. In electrolysis anode is positively charged and cathode is negatively charged. Hence the sign of anode and cathode are ‘+’ and ‘-’ respectively.
FAQs on Cathode and Anode in Electrochemistry
1. What is a cathode and an anode in chemistry?
A cathode is the electrode where reduction occurs, and an anode is the electrode where oxidation occurs in an electrochemical cell. In any redox reaction:
- Oxidation = loss of electrons (occurs at the anode).
- Reduction = gain of electrons (occurs at the cathode).
- Electrons always flow from anode → cathode through the external circuit.
2. What is the difference between cathode and anode?
The main difference between a cathode and an anode is that reduction occurs at the cathode while oxidation occurs at the anode. Key differences include:
- Reaction type: Cathode → reduction; Anode → oxidation.
- Electron flow: Electrons flow from anode to cathode.
- Charge in galvanic cell: Anode (–), Cathode (+).
- Charge in electrolytic cell: Anode (+), Cathode (–).
3. Is the cathode positive or negative?
The cathode is positive in a galvanic (voltaic) cell and negative in an electrolytic cell. This difference occurs because:
- In a galvanic cell, chemical energy produces electricity, so electrons flow toward the cathode, making it positive.
- In an electrolytic cell, an external power source pushes electrons onto the cathode, making it negative.
4. Is the anode positive or negative?
The anode is negative in a galvanic cell and positive in an electrolytic cell. This happens because:
- In a galvanic cell, the anode releases electrons (oxidation), so it becomes negative.
- In an electrolytic cell, the anode is connected to the positive terminal of the power supply.
5. What happens at the cathode during electrolysis?
During electrolysis, reduction occurs at the cathode, meaning species gain electrons. For example, in electrolysis of molten sodium chloride:
- Cathode reaction: Na+(l) + e− → Na(l)
- 2H2O(l) + 2e− → H2(g) + 2OH−(aq)
6. What happens at the anode during electrolysis?
During electrolysis, oxidation occurs at the anode, meaning species lose electrons. For example, in molten sodium chloride:
- Anode reaction: 2Cl−(l) → Cl2(g) + 2e−
- 4OH−(aq) → O2(g) + 2H2O(l) + 4e−
7. How do you identify the cathode and anode in a galvanic cell?
In a galvanic cell, the anode is where oxidation occurs and the cathode is where reduction occurs. To identify them:
- Write the two half-reactions.
- The half-reaction with higher reduction potential is the cathode.
- The other half-reaction is reversed to show oxidation at the anode.
- Zn(s) → Zn2+(aq) + 2e− (anode)
- Cu2+(aq) + 2e− → Cu(s) (cathode)
8. What is the cathode and anode in a Daniell cell?
In a Daniell cell, zinc is the anode and copper is the cathode. The balanced half-reactions are:
- Anode (oxidation): Zn(s) → Zn2+(aq) + 2e−
- Cathode (reduction): Cu2+(aq) + 2e− → Cu(s)
- Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s)
9. Why does oxidation occur at the anode?
Oxidation occurs at the anode because it is the electrode where electrons are released into the external circuit. By definition:
- Oxidation = loss of electrons.
- The anode supplies these electrons to the circuit.
- Zn(s) → Zn2+(aq) + 2e−
10. What is the mnemonic to remember cathode and anode?
A common mnemonic to remember cathode and anode is AN OX, RED CAT, meaning Anode = Oxidation and Reduction = Cathode. This helps you recall that:
- Anode → oxidation (loss of electrons).
- Cathode → reduction (gain of electrons).
- Electrons flow from anode to cathode.
