Question

Which one of the following is not an allotrope of carbon?
A.Soot
B.Graphite
C.Diamond
D.Carborundum

Answer 1

When an element exists in more than one crystalline form, those forms are called allotropes. Well-known forms of carbon include diamond and graphite. Carbon has several allotropes, or different forms in which it can exist. Carborundum is produced by the carbothermal reduction of silica to form an ultra-hard covalently bonded material.

Complete answer:
Carbon is capable of forming many allotropes (structurally different forms of the same element) due to its valency.
Diamond is a well-known allotrope of carbon. The hardness and high dispersion of light of diamond make it useful for both industrial applications and jewellery.
Graphite is one of the most common allotropes of carbon. Unlike diamond, graphite is an electrical conductor. Thus, it can be used in, for instance, electrical arc lamp electrodes.
Soot is a deep black powdery or flaky substance consisting largely of amorphous carbon, produced by the incomplete burning of organic matter. It is also an Allotrope of Carbon.
Carborundum is a man-made crystal also known as Silicon Carbide. In 1891, Edward Goodrich Acheson discovered Carborundum in an attempt to create diamond using electricity. Carborundum energetically purifies the mind, body and spirit while encouraging intuition and discernment. The formula of Carborundum is SiC that is Silicon carbide, and hence, is not an allotrope of carbon.

Therefore, the correct answer is option (D).

Note: Carborundum is a covalent solid, Solids in which constituent particles are held together by a network of covalent bonds throughout the crystal are called covalent solids. Examples: Diamond, graphite, silica (quartz), carborundum (silicon carbide).