Representation of an Electrochemical Cell

Electrochemical cell

An electrochemical cell is a device that can either generate electricity from chemical reactions or a reaction with the help of electricity. Electrochemical cells are of two types- the galvanic cell and the electrolytic cell. A galvanic cell is also known as a Voltaic cell, and it generates electricity from chemical reactions. The electrolytic cell is a type of electrochemical cell that generates a chemical reaction with the help of electricity.

Construction and working of an electrochemical cell

Generally, an electrochemical cell has three parts – an electrolyte and two electrodes. The electrodes are of two types– a cathode and an anode. An anode is an electrode connected to the positive terminal of the external voltage. A cathode is the negative terminal of the external voltage. In the case of a galvanic cell, two types of electrolytes are used. The electrode made of a particular metal is dipped in the beaker containing an electrolyte-rich solution of the same metal ion. For example, if we take zinc and copper electrodes, they are submerged in an aqueous solution of their metallic salts like ZnSO₄ and CuSO₄. The reduction half-reaction occurs in the vessel with the cathode, and the oxidation half-reaction occurs in the vessel with an anode. These two vessels with the reduction and oxidation half-reactions are connected with the help of a salt bridge or a conducting wire. An electric current is formed when the electrons transfer from one container to another. In the case of an electrolytic cell, the cell has three parts – an electrolyte and two electrodes. Like the galvanic cell, the electrolytic cell has a cathode and an anode, with the cathode being connected to the negative terminal of the external voltage and the anode being connected to the positive terminal of the external voltage. When the external voltage is applied across the electrodes, the ions present in the electrolyte are moved towards the electrodes of opposite charges. However, the external voltage applied must be very stable to decompose the electrolyte.

Representation of an electrochemical cell

An electrochemical cell consists of a positive electrode and a negative electrode. The electrolytic solution containing the two types of electrodes are called half cells, and they are represented in a particular way while studying electrochemistry.

Steps to represent an electrochemical cell

1. A galvanic electrochemical cell can be represented by writing the anode on the left-hand side and cathode on the right-hand side.
2. The anode is represented by the solid phase or the metal first, followed by the electrolyte. The cathode of the cell is represented by writing the electrolyte first and then the metal and solid phase.
3. The metal and cation are separated by a semicolon or straight vertical line. The concentration of the electrolyte is also mentioned within the bracket just after the cation.
4. The salt bridge is represented by two vertical lines.

Examples of electrochemical cell representation

1. Ni-AgNO₃( representation of a cell containing Nickel and Silver electrodes)

The oxidation reaction includes the following equation: Ni(s)→Ni₂+ The reduction reaction includes the following equation: 2Ag+(aq) + 2e- → 2Ag(s) The whole reaction can be written as: Ni(s) + 2Ag+(aq) → Ni₂+ (aq) + 2Ag(s) This can be written as the expression given below: Ni | Ni₂+ (aq) || Ag+(aq) | Ag(s)

1. Cu-AgNO₃ (representation of a cell containing copper and silver electrodes)

The oxidation half of the reaction: Cu → Cu₂+ + 2e- The reduction half of the reaction: 2Ag+ +2e- → 2Ag The complete reaction: Cu + 2Ag+ → Cu₂+ + 2Ag The cell is represented as Cu(s) | Cu₂+(aq) || Ag+ (aq) | Ag(s)

Conclusion

An electrochemical cell is a device that uses electrical energy to produce chemical reactions or uses chemical reactions to generate electricity. Electrochemical cells are of two types- galvanic cells and electrolytic cells. The electrochemical cell is represented by separating the cell anode and cathode with the help of two bars or straight lines. These double straight lines represent the salt bridge. The cathode is placed on the right, and the abode is placed on the left. The solid-liquid or aqueous phases are separated with the help of single straight bars. The representation of an electrochemical cell includes all the components involved in the electrochemical cell- the metals, the metal ions, and the salt bridge.