Which of the following is not a use of graphite? (a) For electrodes in batteries. (b) Crucibles made from graphite are used for its inertness to dilute acids and alkalies. (c) For adsorbing poisonous gases. (d) Lubricant at high temperature.

Graphite is revered for its exceptional electrical conductivity among non-metal elements, a characteristic that is influenced by its unique structure. The atoms within graphite are arranged in a honeycomb lattice, forming layers that are bonded by van der Waals forces. This layered arrangement allows electrons to move freely along the planes with minimal resistance, attributing to graphite's ability to efficiently conduct electricity.

Understanding this property is crucial in comprehending why graphite is frequently used in electrical applications. For instance, in batteries, graphite electrodes are integral components because they can handle the high flow of electric current, which is vital for the battery's performance. This explains why option (a) 'For electrodes in batteries' from the exercise is accurate, affirming graphite's role in facilitating the flow of energy in electrochemical cells.

Chemical inertness refers to a substance's ability to resist reaction with other chemicals. Graphite's impressive resistance to chemical reactions makes it an excellent choice for a variety of applications where stability is paramount. Due to its inert nature, graphite does not easily react with acids, bases, or a wide range of chemicals.

This property is exemplified in the use of graphite crucibles for handling high-temperature chemical reactions. The crucibles can withstand exposure to corrosive substances without degrading, which is invaluable in industrial chemical processes. Consequently, option (b) 'Crucibles made from graphite are used for its inertness to dilute acids and alkalies' in the exercise is a correct application of graphite, highlighting its ability to remain stable under chemically aggressive conditions.

Graphite's lubricating properties are tied to its unique physical structure. The layers in graphite are able to slide over each other with ease, contributing to its low friction coefficient. This characteristic allows graphite to act as a high-temperature lubricant in environments where traditional oil-based lubricants would decompose.

For example, graphite is used in hot environments, such as in the production of forged metals or where machinery components are exposed to extreme heat. In these settings, graphite facilitates smooth operation by reducing friction between moving parts. This perfectly aligns with option (d) 'Lubricant at high temperature' from the exercise, reinforcing the relevance of graphite's role as an effective lubricant, especially where other lubricants may fail due to high temperatures.