Question

Terminology

1. Cathode

2.Anode

3. SHE

4. Elecrical double Layer

5. Coulometry

6. Voltammetry

7. Amperometry

8.potentiometry

9. Combination Electrode

10. Alkline Error

Answer 1

1 A cathode is the electrode from which a conventional current leaves a polarized electrical device. (This definition can be recalled by using the mnemonic CCD for cathode current departs.) A conventional current describes the direction in which positive electronic charges move. Electrons have a negative electrical charge, so the movement of electrons is opposite to that of the conventional current flow (consequently, the mnemonic cathode current departs also means that electrons flow into the device's cathode).

2 An anode is an electrode through which conventional current flows into a polarized electrical device. A common mnemonic is ACID for "anode current into device". The direction of (positive) electric current is opposite to the direction of electron flow: (negatively charged) electrons flow out the anode to the outside circuit.

3 The Standard hydrogen electrode (abbreviated SHE), is a redox electrode which forms the basis of the thermodynamic scale of oxidation-reduction potentials. Its absolute electrode potential is estimated to be 4.44 ± 0.02 V at 25 °C, but to form a basis for comparison with all other electrode reactions, hydrogen's standard electrode potential (E⁰) is declared to be zero volts at all temperatures. Potentials of any other electrodes are compared with that of the standard hydrogen electrode at the same temperature.

4 A double layer (DL, also called an electrical double layer, EDL) is a structure that appears on the surface of an object when it is exposed to a fluid. The object might be a solid particle, a gas bubble, a liquid droplet, or a porous body. The DL refers to two parallel layers of charge surrounding the object. The first layer, the surface charge (either positive or negative), consists of ions adsorbed onto the object due to chemical interactions. The second layer is composed of ions attracted to the surface charge via the Coulomb force, electrically screening the first layer. This second layer is loosely associated with the object. It is made of free ions that move in the fluid under the influence of electric attraction and thermal motion rather than being firmly anchored. It is thus called the "diffuse layer".