Calculations based on Compounds Molar mass Practice mole conversions  Check answers from methane problems  Determining formulas based on data  % composition  Empirical formulas  Molecular formulas Objective: To calculate formulas of compounds from data Samples are analyzed to determine type & amount of each component (type of atoms) Chapter 11, pp

Chemistry Essential Standard To analyze quantitatively the composition of a substance (empirical formula, molecular formula, percent composition, and hydrates)  Calculate empirical formula from mass or % composition from experimental data  Calculate molecular formula from empirical formula using molecular weight  Determine the percentage composition by mass of a given compound  Perform calculations based on percent composition  Determine the composition of hydrates using experimental data

Molar Mass for Compounds

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Molar Mass for Compounds Names :

Practice What is the molar mass of Magnesium oxide? What is the number of moles of 60 g of Mg? How many moles are in 40 g of O?

CH ₄ Mole Ammonia side for homework

Methane 1) What is the molar mass of CH ₄ ? 2) How many moles are present in 34 grams of CH ₄ ? 3) How many grams are in 11.5 moles of CH ₄ ? 4) How many moles are there in 3.4 x 10 ²⁴ molecules of CH ₄ ? 5) How many molecules are in 8.5 moles of CH ₄ ?

Mole calculations- methane 6) How many molecules are in 300 grams of CH ₄ ? 7)How many grams are in 5.2 x 10 ²⁴ molecules of CH ₄ ?

Moles & mass (small sheet) 25 g NaCl 2.5 moles NaCl

Hydrate: Copper II Sulfate – Penta Hydrate See Mass and Moles Worksheet 35 grams of CuSO ₄⁃5H₂O 3.2 moles of CuSO ₄⁃5H₂O

Calculations based on Compounds Percent composition of each component in a compound  Based on mass Empirical Formula: formula derived from experimental data  Smallest possible whole number ratio of subscripts Molecular Formula: actual number of atoms of each element (actual subscripts)

Percent Composition – by mass Show the contribution of each component to the mass of the compound Applies to all compounds Nuts & Bolts/Beans

Determining % composition Magnesium chloride Magnesium oxide

Determining % composition Magnesium carbonate Magnesium nitrate

Write the steps to determine % composition 1. First, 2. For each type of atom, the % is calculated by: 3. The answers are checked by …

Video segment

Molecular vs. Empirical Formulas Molecular FormulaEmpirical Formula H2OH2O CH 3 COOH CH 2 O C 6 H 12 O 6 By looking at the compounds above, Predict what type of compounds are used

Empirical Formula Based on analytical data from an unknown sample Steps: Percent to mass Mass to mole Divide by small Multiply ‘til whole

Empirical formula: steps Example 1. A compound consists of 72.2% magnesium and 27.8% nitrogen by mass. What is the empirical formula? Percent to mass Mass to mole Divide by small Multiply ‘til whole

A compound is analyzed and found to contain 68.54% carbon, 8.63% hydrogen, and 22.83% oxygen. The molecular weight of the compound is known to be approximately 140 g/mol. What is the empirical formula? Percent to mass Mass to mole Divide by small Multiply ‘til whole

Video: Empirical formulas

Molecular formulas To calculate molecular formulas, you must know:  Empirical Formula  Molecular mass of the compound

Empirical formula? Molecular mass? A 1.50 g sample of hydrocarbon undergoes complete combustion to produce CO ₂ and H ₂ O. The empirical formula of this compound is CH ₃. Its molecular mass has been determined to be about 78. What is the molecular formula?

Empirical formula? Molecular mass? Caffeine has the following percent composition: carbon 49.48%, hydrogen 5.19%, oxygen 16.48% and nitrogen 28.85%. Its molecular mass is g/mol. What is its molecular formula?