Empirical Formulas and Molecular Formulas ReviewPercent Composition Percent

Empirical Formulas and Molecular Formulas

Review-Percent Composition • Percent Composition – the percentage by mass of each element in a compound (*note: not the ratio of elements in the compound) • Law of Definite Proportions – compounds always contain the same proportions of elements by mass. Part _______ Percent = x 100% Whole So… Mass percent of an Mass of element _______ x 100% element in a compound = _ Mass of compound

Review – Types of Formulas Percent composition allow you to calculate the simplest ratio among the atoms found in compound (Empirical Formula) Empirical Formula – formula of a compound that expresses lowest whole number ratio of atoms. Molecular Formula – actual formula of a compound showing the number of atoms present Examples: C 4 H 10 - molecular ÷ 2 C 2 H 5 C 6 H 12 O 6 - molecular ÷ 6 - empirical CH 2 O - empirical

Determining Molecular Formula From Empirical Formula – Tyler De. Witt

Determining Molecular Formula From Empirical Formula A white powder is analyzed and found to have an empirical formula of P 2 O 5. The compound has a molar mass of 283. 88 g/mol. What is the compound’s molecular formula? Step 1: Molar Mass of Empirical Formula P = 2(30. 974) = 61. 948 O = 5(15. 999) = 79. 995 141. 943 g/mol Step 2: Divide MMF by MEF 283. 88 g/mol 141. 943 g/mol =2 Step 3: Multiply EF by Multiple P 2 O 5 x 2 P 4 O 10

Empirical and Molecular Formula From % Composition – Step-by-Step Science

Calculating Molecular Formula From % Composition A compound has an experimental molar mass of 78 g/mol. Its % composition is found to be 92. 24% carbon and 7. 76% hydrogen. What is its molecular formula of this compound? First, determine the empirical formula using the % composition. Empirical formula of this compound is CH - 1: 1 ratio Determine the multiple Calculate MEF C = 12. 011 g/mol H = 1. 008 g/mol 13. 019 g/mol CH x 6 MMF / MEF = Multiple 78 g/mol =6 13. 019 g/mol C 6 H 6

Homework Read Section 6. 9 in the text Page 298 #1 Page 300 #2 Take the Check Your Understanding Quiz