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Chapter 16: Q38 E (page 704)

Boron nitride (BN) exists in two forms. The first is a slippery solid formed from the reaction of BCI₃ with NH₃, followed by heating in an ammonia atmosphere at 750^oC. Subjecting the first form of BN to a pressure of 85,000 at 1800^oC produces a second form that is the second hardest substance known. Both forms of BN remain solids to 3000^oC. Suggest structures for the two forms of BN.

Short Answer

Expert verified

The two forms of BN are hexagonal closest packing and cubic closest packing.

Step by step solution

01

The first form of BN

The solid formed is slippery and has a hexagonal closest packingform similar to graphite. The atoms B and N₂ are formed by combining very stronger covalent bonds. The slippery compound has the greatest stability and is soft from all of the boron nitride.

02

The second form of BN

The second is the cubic closest packing formwhich corresponds to diamond. The second form is created by high pressure and high-temperature treatment of a hexagonal form of BN and has high thermal and chemical stability.

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Most popular questions from this chapter

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