L25 - Empirical and Molecular Formulas Empirical Formula...

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Unformatted text preview: Empirical and Molecular Formulas Empirical Formula - Molecular Formula - The simplest formula for a compound that agrees with the elemental analysis and gives rise to the smallest set of whole numbers of atoms. The formula of the compound as it exists, it may be a multiple of the empirical formula. Molecular Formula vs. Empirical Formula The empirical formula indicates the relative number of atoms of each element in a molecule (or formula unit). The empirical formula also gives the relative number of moles of each element in the compound. The molecular formula indicates the actual number of atoms of each element in a molecule (it also gives the relative number of moles of each element). It may be a whole-number multiple of the empirical formula. CH 3 C 2 H 6 Ethane HO H 2 O 2 Hydrogen Peroxide H 2 O H 2 O Water Empirical Formula Molecular Formula Compound Name mass(g) of each element Sample Problem 3.4 Determining the Empirical Formula from Masses of Elements PROBLEM: PLAN: SOLUTION: amount(mol) of each element empirical formula Elemental analysis of a sample of an ionic compound showed 2.82 g of Na, 4.35 g of Cl, and 7.83 g of O. What are the empirical formula and name of the compound? preliminary formula change to integer subscripts use # of moles as subscripts divide by M (g/mol) Once we find the relative number of moles of each element, we can divide by the lowest mol amount to find the relative mol ratios (empirical formula). 2.82 g Na mol Na 22.99 g Na = 0.123 mol Na 4.35 g Cl mol Cl 35.45 g Cl = 0.123 mol Cl 7.83 g O mol O 16.00 g O = 0.489 mol O Na 1 Cl 1 O 3.98 NaClO 4 Na 1 Cl 1 O 3.98 NaClO 4 NaClO 4 is sodium perchlorate. Step 1: What is the mass of each element (assuming 100 g of compound)? Determine the empirical formula of the compound with the following composition by mass: 40.0% C, 6.71% H, 53.3% O. Determining the empirical formula of a compound from elemental analysis Step 1: What is the mass of each element (assuming 100 g of compound)? Determine the empirical formula of the compound with the following composition by mass: 40.0% C, 6.71% H, 53.3% O. Determining the empirical formula of a compound from elemental analysis Step 2: How many moles of each element? Step 1: What is the mass of each element (assuming 100 g of compound)?...
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L25 - Empirical and Molecular Formulas Empirical Formula...

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