concept b-f

Topic 6: Stoichiometry

Concept B: Percentage Composition

• Definition: The percentage by mass of each element in a compound.

• Key Vocabulary: Percentage composition, and examples of compounds provided.

Page 1 - Elements and Compounds

• Includes several elements such as Lawrenceium (Lr), Rutherfordium (Rf), Tantalum (Ta), and Tungsten (W).

• Elements presented in a chemical context; possibly an overview of the periodic table with specific focus on select compounds.

Page 2 - Lesson Objectives

• Objectives:

  • Determine percentage composition of a given compound.

• Vocabulary:

  • Percentage composition.

Page 3 - Oxygen Percentage in Compounds

• Question: Which compound has the highest percentage of oxygen?

  • Options:

    • A. CH4O

    • B. CO2

    • C. H2O

    • D. Na2CO3

  • As per question #23.

Page 4 - Practical Examples of Percentage Composition

• Sample Problems:

  • Calculate percentage composition of magnesium phosphate.

  • Calculate mass percentage of water in sodium carbonate decahydrate (Na2CO3∙10H2O).

Page 5 - Try It! Exercises

• Practice Problems:

  1. Calculate the percentage composition of:

  • a. Barium nitrate.

  • b. Ammonium carbonate.

  2. Find mass percentage of water in zinc sulfate heptahydrate.

  • Challenge Question:

    • Determine grams and moles of oxygen in magnesium hydroxide (54.87% oxygen by mass, from 175 g of the compound).

Concept C: Empirical and Molecular Formulas

Page 6 - Overview of Formulas

• Objectives:

  • Calculate empirical formula and molecular formula from experimental data.

• Key Vocabulary:

  • Empirical formula, molecular formula.

Page 7 - Identifying Empirical Formulas

• Question: Identify non-empirical formulas from the following:

  • A. C3H8

  • B. Na2SO4

  • C. Al2(SO4)2

  • D. N2O4

Page 8 - Empirical Formula Definition

• Definition:

  • Empirical formula consists of element symbols with subscripts indicating the smallest whole-number ratio of different atoms.

• Use of Data: Percentage composition data is utilized to derive the empirical formula.

  • Sample Problems:

    • A compound with 32.38% Na, 22.65% S, 44.99% O to determine the empirical formula.

Page 10 - Additional Try It! Exercises

• Exercise Problems:

  1. Find empirical formula given percent compositions.

  2. Determine molecular formulas based on empirical formulas and molar masses.

• Challenge Questions:

  • Analyze a compound with Na, Cl, O where 25.42% is sodium.

Page 11 - Introduction to Stoichiometry

• Vocabulary: Stoichiometry, mole ratio.

• Objectives: Analyze balanced equations for mole ratios and calculate quantities involved in reactions.

Concept D: Stoichiometric Calculations

Page 12 - Basic Stoichiometric Calculations

• Question Example: From the equation Mg + 2HCl -> MgCl2 + H2, how many moles of MgCl2 result from 4 mol HCl?

Page 14 - Understanding Stoichiometry

• Definition: Stoichiometry studies the mass relationships between reactants and products.

  • Mole Ratio: A conversion factor for mole relationships.

  • Sample Problem: Balance Al2O3 -> Al + O2 and write mole ratios.

Page 15 - Problem Types in Stoichiometry

• Four Problem Types:

  1. Amounts in moles.

  2. Moles to grams.

  3. Grams to moles.

  4. Grams to grams via moles.

Concept E: Identifying Reactants

• Objectives: Identify limiting and excess reactants, determine excess remaining.

• Key Vocabulary: Limiting reactant, excess reactant.

Page 17 - Reactant Identification Example

• Question Example: Given reaction C + O2 -> CO2, determine limiting reactant with provided amounts.

Page 18 - Limiting vs. Excess Reactants

• Limiting Reactant: Used up first and limits product formation.

• Excess Reactant: Remains after the reaction completes.

  • Example Problem: Silicon dioxide and hydrogen fluoride reaction.

Page 19 - Further Examples

• Problem Example: Reaction of Fe and H2O producing Fe3O4; determine limiting reactant, mass produced, and excess remaining.

Concept F: Percentage Yield

• Objectives: Distinguish between theoretical and actual yield, calculate percentage yield.

• Key Vocabulary: Theoretical yield, actual yield, percentage yield.

Page 20 - Defining Yield

• Theoretical Yield: Maximum product possible from reactant amounts.

• Actual Yield: Measured amount from a reaction.

• Percentage Yield: Ratio of actual to theoretical yield.

Page 23 - Example of Yield Calculation

• Sample Problem: Calculate percentage yield for chlorobenzene from given reactants.

Page 24 - Practical Yield Calculations

• Additional Example Problems:

  1. Determine percentage yield of methanol from carbon monoxide and hydrogen gas.

  2. Calculate mass of copper produced from aluminum reacting with copper(II) sulfate.

Key Vocabulary:

• Percentage composition: The percentage by mass of each element in a compound.

• Empirical formula: Consists of element symbols with subscripts indicating the smallest whole-number ratio of different atoms.

• Molecular formula: Indicates the actual number of atoms of each element in a molecule of a substance.

• Stoichiometry: The study of the mass relationships between reactants and products in chemical reactions.

• Mole ratio: A conversion factor for mole relationships derived from balanced equations.

• Limiting reactant: The reactant that is used up first and limits product formation in a chemical reaction.

• Excess reactant: The reactant that remains after the reaction has completed.

• Theoretical yield: The maximum amount of product that can be formed from given reactants under ideal conditions.

• Actual yield: The measured amount of a product obtained from a chemical reaction.

• Percentage yield: The ratio of actual yield to theoretical yield, expressed as a percentage.