Question

Question: Boron nitride (BN) is made by the reaction of boron trichloride with ammonia.

(a) Write a balanced chemical equation for this reaction.

(b) Calculate the standard enthalpy change per mole of BN produced, given that the standard molar enthalpy of formation of BN(s) is 254.4 kJ mol21 .

(c) Predict (qualitatively) the following physical properties of boron nitride: conductivity, melting point, and hardness.

Short answer

Answer

Step-by-step solution

Boron nitride

The compound boron nitride plays an important role as a lubricant. It is used in paints, dental cements, pencils etc. It is also used as a refractory material. It is used even in cosmetics.

Subpart (a)

$BC{l}_3\left(g\right)+N{H}_3\left(g\right)\to BN\left(s\right)+3HCl\left(g\right)$

The formation of boron nitride in the form of chemical equation is as shown below:

Subpart (b)

The standard enthalpy change of a chemical reaction can be obtained as:

$$\begin{gathered} ∆{H^0}_{rxn}=\sum _{}∆{H^0}_{products}-\sum _{}∆{H^0}_{reactents} \\ =1\left(-254.4\right)+3\left(-92.31\right)-1\left(-403.76\right)-1\left(-46.11\right) \\ =-81.46 kJ \end{gathered}$$

Thus, the per mole of BN(s) is$-81.46 kJ$