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Unformatted text preview: 1 Composition Stoichiometry Principles of General Chemistry, 2 nd ed. By M. Silberberg Chemistry, 8th ed. by W. Whitten, R. Davis, R., M. L. Peck, and G. Stanley. continued… 2 Lecture • Derivation of Formulas from Elemental Composition • Determination of Molecular Formulas • Purity of Samples 3 Derivation of Formulas from Elemental Composition • Empirical Formula - smallest whole-number ratio of atoms present in a compound – CH 2 is the empirical formula for alkenes – No alkene exists that has 1 C and 2 H’s • Molecular Formula - actual numbers of atoms of each element present in a molecule of the compound – Ethene – C 2 H 4 – Pentene – C 5 H 10 4 We determine the empirical and molecular formulas of a compound from the percent composition of the compound. Derivation of Formulas from Elemental Composition 5 • Example: A compound contains 24.74% K, 34.76% Mn, and 40.50% O by mass. What is its empirical formula?...
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