Elemental boron can be formed by reaction of boron trichloride with hydrogen. BCl₃(g) + 1.5H₂(g) → B(s) + 3HCl(g)
Calculate ΔG° for the reaction.

Question

Elemental boron can be formed by reaction of boron trichloride with hydrogen. BCl₃(g) + 1.5H₂(g) → B(s) + 3HCl(g) Calculate ΔG° for the reaction.

Quizplus · Accepted Answer

We can use the equation ΔG° = ΔH° - TΔS°, where ΔH° and ΔS° are the standard enthalpy and entropy changes, respectively, and T is the temperature in Kelvin.

To find ΔH°, we can use the bond energies of the reactants and products:

ΔH° = [Σ(bond energies of products)] - [Σ(bond energies of reactants)]
ΔH° = [0] - [B-Cl: 243 + B-H: 391.7 + H-Cl: 431] = -1066.7 kJ/mol

To find ΔS°, we can use standard entropy data:

ΔS° = [Σ(S° of products)] - [Σ(S° of reactants)]
ΔS° = [0] - [B: 5.7 + BCl3: 241.8 + 1.5H2: 130.6 + 3HCl: -92.3] = 174.4 J/K·mol

Now we can plug in these values into the equation:

ΔG° = -1066.7 kJ/mol - 298 K * (174.4 J/K·mol / 1000 J/kJ) = -102.8 kJ/mol

Therefore, the answer is choice D, -102.8 kJ.

Elemental Boron Can Be Formed by Reaction of Boron Trichloride