Final answer:
The empirical formula of boron oxide is determined by converting the mass of boron and oxygen to moles, finding the mole ratio, and simplifying to the nearest whole number ratio, which is B2O3.
Step-by-step explanation:
To find the empirical formula of boron oxide, we first convert the mass of the elements to moles. The atomic mass of boron (B) is approximately 10.81 g/mol, and the atomic mass of oxygen (O) is approximately 16.00 g/mol. With a 43.6 mg (or 0.0436 g) sample of boron, we have:
Number of moles of boron = 0.0436 g / 10.81 g/mol = 0.00403 moles
Since the total mass of boron oxide is 140 mg (or 0.140 g), the mass of oxygen in the compound is:
Mass of oxygen = total mass of compound - mass of boron = 0.140 g - 0.0436 g = 0.0964 gNumber of moles of oxygen = 0.0964 g / 16.00 g/mol = 0.00602 moles
The mole ratio of boron to oxygen is approximately 1:1.5, which simplifies to 2:3 when rounded to the nearest whole number. Therefore, the empirical formula of boron oxide is B2O3, or option C) B2O3.