Question

Which of the following statements about boron carbide is wrong?
(A) Its molecular formula is ${B_4}C$
(B) It is also called Norbia
(C) It is the hardest Substance
(D) It is used for cutting glasses

Answer 1

To solve this question you should know about the structure, properties, and manufacturing process of Boron Carbide. It was invented in the ${19^{th}}$ century as a by-product in the metal borides production and now has wide applications in the industry.

Complete step by step answer
Boron carbide is a rhombohedron lattice crystal of Boron and Carbon. Its molecular formula is ${B_4}C$ . It has a melting point of $2445$ making it one of the hardest and inert materials known to exist on earth.
It is synthesised by reducing Boron Trioxide ( ${B_2}{O_3}$ ) with Carbon in presence of carbon or Magnesium in an arc furnace. $CO(g)$ is liberated in this reaction.
$2{B_2}{O_3}\, + \,7C \to \,{B_4}C\, + 6CO(g)$
It is the third-highest hardest substance after Diamond and Cubic Boron Nitride with mohr hardness of $7 - 9$ .
As the hardness of ${B_4}C$ is very high its powder is used in polishing and lapping applications, and in cutting applications such as water jet cutting as an abrasive. It is also used for dressing diamond tools.
${B_4}C$ is also used as a coating on a suitable substrate with the help of vapour phase reaction techniques. For example; using Di-borane with $C{H_4}$ .
Due to its high abrasive properties and hardness, it is used in tank armors, vest proofs, and also called as ‘Black Diamond’ or ‘Norbia’.
Hence, Option (C) is correct.

Note
The structure of ${B_4}C$ has boron atoms in icosahedral groups of 12, and the carbon atoms are in a linear chain of three. For commercial purposes, its powder is also used to remove metallic impurities. It is also used as a Neutron absorber in the Nuclear Reactors and as nozzles for slurry pumping, grit blasting.