A compound has the following percentage composition, by weight: 22.0% Cu, 12.9% Fe, 16.6% C, 19.4% N, and 29.1% H₂O. Write a plausible (empirical) formula for this hydrate.

Question

Quizplus · Accepted Answer

- The empirical formula should reflect the smallest whole number ratios of the elements in the compound. - To determine the empirical formula, we need to find the mole ratios of the elements. - Assume we have 100g of the compound, then we have: - 22.0g Cu - 12.9g Fe - 16.6g C - 19.4g N - 29.1g H₂O - Convert each of the masses to moles: - 22.0g Cu / 63.55 g/mol Cu = 0.346 moles Cu - 12.9g Fe / 55.85 g/mol Fe = 0.231 moles Fe - 16.6g C / 12.01 g/mol C = 1.38 moles C - 19.4g N / 14.01 g/mol N = 1.39 moles N - 29.1g H₂O / 230.27 g/mol H₂O = 0.126 moles H₂O - Find the mole ratios by dividing each by the smallest number of moles: - Cu: 0.346 / 0.126 ≈ 2.75 - Fe: 0.231 / 0.126 ≈ 1.84 - C: 1.38 / 0.126 ≈ 10.95 - N: 1.39 / 0.126 ≈ 11.03 - H₂O: 0.126 / 0.126 = 1 - Round each to the nearest whole number to get the empirical formula: - Cu3Fe2C11N11H12SO14 - This formula matches option C, Cu₃Fe₂(CN)₁₂ ∙ 14 H₂O.

A Compound Has the Following Percentage Composition, by Weight: 22