Calculate the number of moles represented by 21.7 g Fe.

Question

BlackTom AI · Accepted Answer

Start by identifying what the question asks: the number of moles represented by 21.7 g of iron (Fe).
Option a: 1.20 moles. To check, multiply 1.20 moles by the molar mass of Fe (≈55.85 g/mol) gives about 66.98 g, which is far from 21.7 g. This is not consistent with the given mass, so this option is incorrect.
Option b: 1210 moles. This would correspond to a mass around 1210 × 55.85 ≈ 67,623 g, vastly larger than 21.7 g. Clearly unrealistic for the provided mass, so this option is incorrect.
Option c: 0.835 moles. If this were true, the corresponding mass would be 0.835 × 55.85 ≈ 46.7 g, which does not match the given 21.7 g. Therefore, this option is incorrect.
Option d: 2.57 moles. Converting back would require 2.57 × 55.85 ≈ 143.6 g, again not equal to 21.7 g. This shows a mismatch, so this option is incorrect.
Option e: 0.389 moles. This aligns with the mole calculation: moles = mass ÷ molar mass. Using Fe’s molar mass ≈ 55.85 g/mol, 21.7 g ÷ 55.85 g/mol ≈ 0.389 moles. The result matches the mass provided, making this option consistent with the fundamental formula.
Further clarification: the core concept here is mole conversion via M = m/n, or more familiarly n = m/M, where M is the molar mass. Since Fe has a molar mass around 55.85 g/mol, dividing 21.7 g by 55.85 g/mol yields a value near 0.389 moles, confirming the calculation.
In summary, the mismatches in options a–d arise from using incorrect multiples of Fe’s molar mass or misplacing decimal points, whereas option e correctly applies the molar mass to convert grams to moles for iron.

Calculate the number of moles represented by 21.7 g Fe.单项选择题

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