Elemental boron can be formed by the reaction of boron trichloride with hydrogen. 2BCl₃(g) + 3H₂(g) → 2B(s) + 6HCl(g) What is ΔG°_rxn for this reaction? A) -293.4 kJ/mol B) 293.4 kJ/mol C) -205.6 kJ/mol D) 205.6 kJ/mol E) -2141.6 kJ/mol

Question

Quizplus · Accepted Answer

We can use the equation ΔG°_rxn = ΔH°_rxn - TΔS°_rxn First, we need to calculate ΔH°_rxn: 2BCl₃(g) + 3H₂(g) → 2B(s) + 6HCl(g) ΔH°_rxn = ΣΔH°_f(products) - ΣΔH°_f(reactants) ΔH°_rxn = 2(0 kJ/mol) + 6(-92.31 kJ/mol) - 2(-397.9 kJ/mol) - 3(0 kJ/mol) ΔH°_rxn = -205.6 kJ/mol Next, we need to calculate ΔS°_rxn: ΔS°_rxn = ΣS°_f(products) - ΣS°_f(reactants) ΔS°_rxn = 2(5.69 J/mol•K) + 6(186.9 J/mol•K) - 2(251.7 J/mol•K) - 3(130.6 J/mol•K) ΔS°_rxn = -476.4 J/mol•K Finally, we can calculate ΔG°_rxn at standard conditions (298 K, 1 atm): ΔG°_rxn = ΔH°_rxn - TΔS°_rxn ΔG°_rxn = (-205.6 kJ/mol) - (298 K)(-0.4764 kJ/mol) ΔG°_rxn = -205.6 kJ/mol + 142.2 kJ/mol ΔG°_rxn = -63.4 kJ/mol Rounding to one decimal place, we get ΔG°_rxn = -63.4 kJ/mol, which is closest to answer choice D.

Elemental Boron Can Be Formed by the Reaction of Boron