Final answer:
The mass of boric oxide formed from the decomposition of 15.0 g of B(OH)₃ is 11.0 g.
Step-by-step explanation:
To find the mass of boric oxide formed from the decomposition of 15.0 g of B(OH)₃, we need to use the stoichiometric coefficients from the balanced chemical equation.
From the equation: 2 B(OH)₃(s) → B₂O₃(s) + 3 H₂0(g), we can see that the molar ratio between B(OH)₃ and B₂O₃ is 2:1.
To calculate the mass of B₂O₃ formed, we will multiply the molar mass of B₂O₃ by the ratio of B₂O₃ to B(OH)₃:
Molar mass of B₂O₃ = 2 × Atomic mass of B + 3 × Atomic mass of O = 2 × 10.81 g/mol + 3 × 16.00 g/mol = 69.62 g/mol.
Now we can calculate:
Mass of B₂O₃ formed = (15.0 g B(OH)₃) × (1 mol B₂O₃/2 mol B(OH)₃) × (69.62 g/mol) = 11.0 g B₂O₃.