The empirical formula of a compound with a mass percent composition of 6.78% H, 31.43% N, 39.76% Cl, and 22.03% Co is consistent with which of the following complexes? A) [Co(NH₃)₄Cl₂]Cl B) [Co(NH₃)₃Cl₃] C) [Co(NH₃)₆]Cl₃ D) [Co(NH₃)₅Cl]Cl₂ E) none of these

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Quizplus · Accepted Answer

Calculate the empirical formula using the mass percent composition: - Assume 100 g sample, then you have 6.78 g H, 31.43 g N, 39.76 g Cl, and 22.03 g Co. - Convert all masses to moles: H: 6.73 mol, N: 2.25 mol, Cl: 1.12 mol, Co: 0.16 mol - Divide all mole values by the smallest mole value to get the simplest mole ratio: H: 3, N: 1, Cl: 2, Co: 0.5 - Multiply all mole values by 2 to get integer values: H: 6, N: 2, Cl: 4, Co: 1 - The empirical formula is CoN2Cl4H6 To check which complex matches this empirical formula, we need to look at the ligands attached to the central cobalt atom. The formula of each ligand is: - NH₃: imidazole-4-carboxamide - ₃: 2-mercaptobenzothiazole - ₄Cl₂: 2-chloromethylthio-1,3-benzothiazole - ₆: 2,2’-dipyridylamine None of the ligands match the formula H6N2Cl4, except for complex C: [Co(NH₃)₆]Cl₃, which has 2 N, 6 H, 1 Co, and 4 Cl atoms. Therefore, the answer is C.

The Empirical Formula of a Compound with a Mass Percent