Chapter 10 Chemical Quantities 10.1 The Mole: A Measurement of Matter 10.2 Mole-Mass and Mole-Volume Relationships 10.3 Percent Composition and Chemical Formulas Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Percent Composition of a Compound percent composition: percent by mass of each element in a compound Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Percent Composition of a Compound Percent Composition from the Chemical Formula % by mass of element mass of element in 1 mol compound molar mass of compound × 100% = Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Percent Composition of a Compound Percent Composition from the Chemical Formula Calculate the percent composition of a) Al(OH)3 b) K2S Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Percent Composition of a Compound Percent Composition from the Chemical Formula Calculate the percent composition of a) Al(OH)3 Al: 34.6%, O: 61.5%, H: 3.9% b) K2S K: 70.9%, S: 29.1% Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Percent Composition of a Compound Percent Composition from Mass Data % by mass of element = mass of element mass of compound × 100% Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Calculate the mass of nitrogen and the mass of hydrogen in Sample Problem 10.11 Calculating the Mass of an Element in a Compound Using Percent Composition Calculate the mass of nitrogen and the mass of hydrogen in 125 g of NH3 fertilizer. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

1. Calculate the % composition for each component. Sample Problem 10.11 1. Calculate the % composition for each component. 14.0 g N 17.0 g NH3 3.0 g H 17.0 g NH3 % N = = 82.35% % H = =17.65% 2. Multiply each % composition by the mass of NH3. 125 g NH3 × 0.8235 = 103 g N 125 g NH3 × 0.1765 = 22 g H Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Does the result make sense? Sample Problem 10.11 Does the result make sense? The sum of the two masses equals 125 g, (103 g N + 22 g H = 125 g NH3). Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Calculate the masses of hydrogen, sulfur, and oxygen in 90 Calculate the masses of hydrogen, sulfur, and oxygen in 90.0 g of H2SO4. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Calculate the masses of hydrogen, sulfur, and oxygen in 90 Calculate the masses of hydrogen, sulfur, and oxygen in 90.0 g of H2SO4. Hydrogen: 1.8 g Sulfur: 29.4 g Oxygen: 58.8 g Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

When a 14.2-g sample of HgO is decomposed into its elements by heating, 13.2 g Hg is obtained. What is the percent composition of the compound? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

mass of Hg × 100% % Hg = mass of compound 13.20 g = 14.20 g = 93.0% Hg Sample Problem 10.9 % Hg = mass of Hg mass of compound × 100% = 93.0% Hg = 13.20 g 14.20 g Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

mass of O × 100% % O = mass of compound 1.0 g = 14.2 g = 7.0% O Sample Problem 10.9 % O = mass of O mass of compound × 100% 1.0 g = 7.0% O = 14.2 g Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Check that percents add up to 100%. 93.0% + 7.0% = 100% Sample Problem 10.9 Does the result make sense? Check that percents add up to 100%. 93.0% + 7.0% = 100% Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Do Now: Calculate the percent composition of acetylene, C2H2. C2H2 is used in welder’s torches. 2. Calculate the percent composition of styrene, C8H8. Styrene is used to make polystyrene. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Empirical Formulas empirical formula: lowest whole-number ratio of atoms or moles of elements in a compound. Compound Molecular Formula Empirical Formula Hydrogen Peroxide H2O2 HO Water H2O Sucrose C6H12O6 CH2O Acetylene C2H2 CH Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Determining the Empirical Formula of a Compound Sample Problem 10.12 Determining the Empirical Formula of a Compound A compound is analyzed and found to contain 25.9% nitrogen and 74.1% oxygen. What is the empirical formula of the compound? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Empirical Formula Determination Start with percent composition Empirical Formulas Empirical Formula Determination Start with percent composition Assume you have 100 g of compound. The % composition will equal the mass of each element. Convert each mass to moles. Determine lowest whole number mole ratio Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Analyze List the knowns and the unknown. Sample Problem 10.12 Analyze List the knowns and the unknown. 1 KNOWNS percent by mass of N = 25.9% N percent by mass of O = 74.1% O Assuming there is 100 g of compound, then you would have 25.9 g N and 74.1 g O UNKNOWN empirical formula = N?O? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Calculate Solve for the unknown. Sample Problem 10.12 Calculate Solve for the unknown. 2 Convert mass to moles. 25.9 g N × 1 mol N 14.0 g N = 1.85 mol N 74.1 g O × 1 mol O 16.0 g O = 4.63 mol O The mole ratio of N to O is N1.85O4.63. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Calculate Solve for the unknown. Sample Problem 10.12 Calculate Solve for the unknown. 2 Divide each molar quantity by the smaller number of moles to get 1 mol for the element with the smaller number of moles. 1.85 mol N 1.85 = 1 mol N 4.63 mol O 1.85 = 2.50 mol O The mole ratio of N to O is N1O2.5. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Calculate Solve for the unknown. Sample Problem 10.12 Calculate Solve for the unknown. 2 Multiply each part of the ratio by the smallest whole number that will convert both subscripts to whole numbers. 1 mol N × 2 = 2 mol N 2.5 mol O × 2 = 5 mol O The empirical formula is N2O5. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

A compound is analyzed and found to contain: 36.1% Ca 63.9% Cl What is the empirical formula for the compound? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

A compound is analyzed and found to contain: 36.1% Ca 63.9% Cl What is the empirical formula for the compound? CaCl2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Finding the Molecular Formula of a Compound Sample Problem 10.13 Finding the Molecular Formula of a Compound Calculate the empirical formula mass. Divide the molar mass by the empirical formula mass. Multiply the empirical formula subscripts by the answer from step 2. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Finding the Molecular Formula of a Compound Sample Problem 10.13 Finding the Molecular Formula of a Compound Calculate the molecular formula of a compound whose molar mass is 60.0 g/mol and empirical formula is CH4N. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

1. Calculate the empirical formula mass (efm). Sample Problem 10.13 1. Calculate the empirical formula mass (efm). efm of CH4N = 12.0 g/mol + 4(1.0 g/mol) + 14.0 g/mol = 30.0 g/mol Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

2. Divide the molar mass by the empirical formula mass. Sample Problem 10.13 2. Divide the molar mass by the empirical formula mass. molar mass efm = 60.0 g/mol 30.0 g/mol = 2 3. Multiply the formula subscripts by this value. (CH4N) × 2 = C2H8N2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Evaluate Does the result make sense? Sample Problem 10.13 Evaluate Does the result make sense? 3 The molecular formula has the molar mass of the compound. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

A compound is composed of carbon and hydrogen and has a molar mass of 86.0 g/mol. It’s empirical formula is C3H7. What is the molecular formula? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

A compound is composed of carbon and hydrogen and has a molar mass of 86.0 g/mol. It’s empirical formula is C3H7. What is the molecular formula? C6H14 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Calculate the grams of nitrogen in 125 g of NH4NO3. Do Now: Calculate the grams of nitrogen in 125 g of NH4NO3. Calculate the empirical formula for a compound that is 94.1% O and 5.9% H. What is the empirical formula for C6H12O6? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Calculate the grams of nitrogen in 125 g of NH4NO3. 43.8 g Do Now: Calculate the grams of nitrogen in 125 g of NH4NO3. 43.8 g Calculate the empirical formula for a compound that is 94.1% O and 5.9% H. OH What is the empirical formula for C6H12O6? CH2O Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

A compound is analyzed and found to contain: 40% C 6.7% H 53.3% O What is the empirical formula for the compound? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

A compound is analyzed and found to contain: 40% C 6.7% H 53.3% O What is the empirical formula for the compound? CH2O Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

A compound is analyzed and found to contain: 3.7% H 44.4% C 51.9% N What is the empirical formula for the compound? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

A compound is analyzed and found to contain: 3.7% H 44.4% C 51.9% N What is the empirical formula for the compound? HCN Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

END OF 10.3 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

What is the density of N2 gas at STP? Do Now: What is the density of N2 gas at STP? A gas has a density of 0.791 g/L. What is the molar mass of this gas? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

What is the density of N2 gas at STP? 1.25 g/L Do Now: What is the density of N2 gas at STP? 1.25 g/L A gas has a density of 0.791 g/L. What is the molar mass of this gas? 17.7 g/mol Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Take out the “OREO” lab handout. Do Now: Sit with your lab group. Take out the “OREO” lab handout. Work through the last 4 problems on the back of the lab handout. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.