Question

A form of non-metal which is used for making an electrode in electrolytic cells is:
A. graphite
B. diamond
C. copper
D. sulfur

Answer 1

Electrochemistry is a wide subject and Nernst equation and corrosion are a part of it. The Nernst equation is used to calculate the cell potential of an electrochemical cell at any given temperature, pressure, and reactant concentration.

Complete step by step answer:
Generally, metals are used as electrodes. The more electropositive electron generates electrons which are used as an anode. And less electropositive metals accept electrons and act as a cathode.
But in the case of graphite due to layer structure and weak Vander waals force it can conduct electricity. Due to this nature being a non- metal graphite is used as an electrode.
So, the correct answer is, A.

Additional information:
In the Hall-Heroult process, pure aluminum oxide or alumina $(A{l_2}{O_3})$ is combined with $Na{F_2}$ or $N{a_3}[Al{F_6}]$ which results in the lowering of the melting point of the mixture, and the ability to conduct electricity increases. A steel vessel that is lined with carbon and graphite rods is used in this process.
The carbon lining is used as the cathode whereas the graphite rods are used as anodes. Upon passage of electricity through the electrolytic cell, oxygen is produced at the anode. This oxygen reacts with the carbon of the anode, to form carbon monoxide and carbon dioxide.
The reaction at the cathode is:
$A{l^{3 + }} + 3{e^ - } \to Al(l)$
The reaction at the anode:

$$C(s) + {O^{2 - }} \to CO(g) + 2{e^ - } \\\ C(s) + 2{O^{2 - }} \to C{O_2}(g) + 4{e^ - } \\\$$

Note: When stainless steel is joined with carbon steel, for example, stainless tubes and carbon-steel tubes in a heat exchanger, the carbon steel may suffer from galvanic corrosion attack. When stainless steel is combined with graphite, the attack will be on the steel. Graphite gaskets should therefore be avoided.
When graphite is converted to diamonds, bonds breaking require a high amount of heat as graphite is stable, and thus it is also an endothermic reaction.
${C_2}{H_6} \to {C_2}{H_4} + {H_2}$
${C_{graphite}} \to {C_{diamond}}$