What amount (moles) is represented by each of these samples? a. 150.0 g Fe_ \(\mathrm{O}_{3}\) b. 10.0 \(\mathrm{mg} \mathrm{NO}_{2}\) c. \(1.5 \times 10^{16}\) molecules of \(\mathrm{BF}_{3}\)

We first need to determine the molar mass for each compound, using the periodic table. a. Fe₂O₃ (Iron(III) oxide): Fe - 55.85 g/mol O - 16.00 g/mol Molar mass of Fe₂O₃ = (2 x 55.85) + (3 x 16.00) = 111.70 + 48.00 = 159.70 g/mol b. NO₂ (Nitrogen dioxide): N - 14.01 g/mol O - 16.00 g/mol Molar mass of NO₂ = 14.01 + (2 x 16.00) = 14.01 + 32.00 = 46.01 g/mol c. BF₃ (Boron trifluoride): B - 10.81 g/mol F - 19.00 g/mol Molar mass of BF₃ = 10.81 + (3 x 19.00) = 10.81 + 57.00 = 67.81 g/mol

Now that we have the molar mass for each compound, we can convert the given mass to moles using the formula: Moles = (Given mass) / (Molar mass) a. 150.0 g of Fe₂O₃: Moles of Fe₂O₃ = 150.0 g / 159.70 g/mol = 0.939 moles b. 10.0 mg of NO₂: First, we need to convert milligrams to grams: 10 mg = 10 × 10⁻³ g = 0.010 g Moles of NO₂ = 0.010 g / 46.01 g/mol = 2.17 × 10⁻⁴ moles c. 1.5 × 10¹⁶ molecules of BF₃: In this case, the substance is given in molecules and not in mass. We will use Avogadro's number (6.022 × 10²³) to convert it to moles: Moles = (Given molecules) / (Avogadro's number) Moles of BF₃ = (1.5 × 10¹⁶) / (6.022 × 10²³) = 2.49 × 10⁻⁸ moles Final answer: a. 0.939 moles of Fe₂O₃ b. 2.17 × 10⁻⁴ moles of NO₂ c. 2.49 × 10⁻⁸ moles of BF₃