Question

Bone black is a polymorphic form of
(A) Phosphorus
(B) Sulphur
(C) Carbon
(D) Nitrogen

Answer 1

Hint: Polymorphism is the condition in which a chemical compound exists in more than one crystalline form. The form can differ in physical properties and chemical properties but their solutions and vapor are identical. The other polymorphic forms of the compound are red and white.

Complete Step by step solution
Phosphorus is an element denoted with symbol P and has atomic number 15. Phosphorus exists in two major forms which are white phosphorus and red phosphorus. These are two allotropes of phosphorus out of the major three. Allotropes possess different physical forms in which an element can exist, but when the molecule of pure atoms is packed in different crystalline solids then they are called polymorphs.
Some of the polymorphs of phosphorus are:
White phosphorus: White or yellow or tetra phosphorus exists as a molecule made up of four atoms of phosphorus. The molecule consists of six P-P bonds. It has two forms, alpha and beta.
Red phosphorus: It is formed by heating white phosphorus in absence of air or by exposing it to sunlight. Red phosphorus exists as an amorphous network.
Black phosphorus: It is a thermodynamically stable form of phosphorus at room temperature and pressure. It is made by heating white phosphorus under high pressure.
Bone black which is also known as bone char; is porous, black, granular material produced by charring animals’ bones. Charring means heating or burning of bone in the presence of a limited amount of air. Bone black is also a polymorphic form of phosphorus.
Therefore, the correct answer is option A.

Note
Bone black is used in water treatment, sugar refining, black pigmentation and refining crude oil. Bone black is used in removing colored impurities from liquids, especially solutions of raw sugar. Red phosphorus is used as a catalyst/reagent in organic reactions.