Final answer:
To calculate the amount of iron in 15.8 g of Fe(OH)3, convert the mass to moles and then to grams of iron, resulting in 8.26 grams of Fe.
Step-by-step explanation:
To find out how many grams of iron (Fe) are contained in 15.8 g of Fe(OH)3, we need to first calculate the molar mass of Fe(OH)3 and determine the percentage by mass of iron in that compound. The molar mass of Fe(OH)3 is calculated as follows: (1×55.85) + (3×16.00) + (3×1.008) ≈ 106.867 g/mol. Now, the number of moles of Fe(OH)3 we have in 15.8 g is calculated by dividing the mass of Fe(OH)3 by its molar mass:
15.8 g / 106.867 g/mol ≈ 0.1478 moles of Fe(OH)3.
Since there is one mole of Fe for each mole of Fe(OH)3, we have 0.1478 moles of Fe. To find the mass of Fe, we multiply the number of moles of Fe by the molar mass of Fe (55.85 g/mol):
0.1478 moles × 55.85 g/mol ≈ 8.26 grams of Fe.
Therefore, the correct answer is b. 8.26 g of Fe contained in 15.8 g of Fe(OH)3.