2. Mass % and % Composition Mass % = grams of element grams of compound X 100 % 8.20 g of Mg combines with 5.40 g of O to form a compound. What is the mass % of Mg? Percent composition is the mass % for each one of the elements in a compound. What is the percent composition of the compound mentioned above. What is the percent composition of sulfuric acid? What is the mass of carbon in 82.0 g of ethane (C 2 H 6 )

3. Empirical and Molecular Formulas Empirical Formula - Lowest whole # ratio of elements in a compound Molecular Formula -Actual formula of compound The empirical formula is determined using experimental composition data to calculate element ratios (mole ratios). The molecular formula is calculated from the empirical formula and the formula mass (mass spectrometer).

4. Empirical Formulas The simplest, whole-number ratio of atoms in a molecule is called the Empirical Formula The simplest, whole-number ratio of atoms in a molecule is called the Empirical Formula can be determined from percent composition or from mass data.can be determined from percent composition or from mass data. Poem to Calculate Empirical Formula Poem to Calculate Empirical Formula Percent to Mass (optional) Mass to Mole Divide by Small Multiply ‘til Whole

5. Empirical and Molecular Formulas Determine the empirical formula of a compound that is 40.0% C, 6.72% H, and 53.3% O 40.0 g C x 1 mol 12.01 g = 6.72 g H x 1 mol 1.01 g = 53.3 g O x 1 mol 16.00 g = 3.33 mol 6.65 mol 3.33 mol = = = Empirical Formula = If the molar mass of this compound is 180.1g/mol, what is the molecular formula?

6. Empirical and Molecular Formulas Vitamin C (ascorbic acid) is composed of 40.92% C, 4.58% H, and 54.50% O. What is the empirical formula? If the molar mass of ascorbic acid is 176.0 g/mol, what is the molecular formula?

7. 0.450 g of caproic acid ( a compound which contains only H, C, and O) combusted in oxygen gives 0.418 g H 2 O and 1.023 g CO 2. If the molar mass is 116.2 g/mol, what is the molecular formula? Determining the Formula from Elemental Analysis: When 0.1156 g of a compound containing C, H, and N is reacted with oxygen, 0.1638 g of CO 2 and 0.1676 g of H 2 O are formed. Assuming all of the carbon is converted to CO 2 and the molar mass of the compound is 62.0 g/mol, what is the formula for this compound?

8. By Elemental Analysis If a sample of ammonium carbonate contains 8.00 x 10 22 hydrogen atoms, what mass does it have?

9. By Elemental Analysis If a sample of magnesium nitrate contains 8.00 x 10 22 oxygen atoms, what mass does it have?