| Monday January 29, 2023 Day 15 Composition and Mass Percent of Compounds |
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| Textbook Readings: Determining Empirical and Molecular Formulas First part of this section |
Course Lectures 3.1 pdf Video* Introduction to the mole (middle section) |
| Objectives 1. Determine molar masses given a chemical formula. 2. Use the molar mass and individual atomic contributions to determine the percent composition of an element in a compound. 3. Given mass percents, determine elemental masses for arbitrary samples. |
Percent Composition by Mass |
Homework Problems 15.1 Using atomic masses from your periodic table, determine the mass percent of sodium and chlorine in NaCl. Demonstrate that the masses you calculate add up to 100% as they should. 15.2 Determine the mass percent of carbon and hydrogen in CH3CH2CH3. Demonstrate that the masses you calculate add up to 100% as they should. 15.3 Determine the mass percent of copper, nitrogen and oxygen for Cu(NO3)2 Demonstrate that the masses you calculate add up to 100% as they should. 15.4 A compound is known to contain 3 elements: iron, sulfur and oxygen. What is the mass percent of iron present if 46.656% of the compound is sulfur and 20.557 % of the compound is oxygen. 15.5 Given a 25.0 gram sample of solid Cu(NO3)3, determine the individual mass contributions for copper, oxygen and nitrogen. 15.6 In a 75.0 grams sample of Al2(SO4)3, determine the mass contributions of aluminum, sulfur and oxygen. Click and Drag below for answers 15.1 39.337 %Na + 60.663 %Cl = 100.000% 15.2 81.714 %C + 18.286 %H = 100.000% 15.3 33.881 %Cu + 14.936 %N + 51.183 %O = 100.000% 15.4 32.787 %O 15.5 6.37 g Cu 4.21 g N 14.42 g O (All add up to 25 grams) 15.6 11.8 g Al 21.1 g S 42.1 g O (All add up to 75.0) |
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| Tuesday January 30, 2024 Day 16 Empirical and Molecular Formulae: Combustion Analysis |
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| Textbook Readings: Determining Empirical and Molecular Formulas Combustion Analysis |
Course Lectures 3.1 pdf Video* Introduction to the mole (last section) |
| Determining Empirical and Molecular Formulas |
Combustion Analysis |
| Objectives 1. When working with mass percents, assume 100 grams total 2. Use mass percents into grams, and moles for each element 3. Analyze elemental moles and determine the empirical formula for the compound 4. Given a molecular mass, use the empirical formula to determine the molecular formula 5. Use the results of a combusion analysis to determine the empirical and molecular formulae for a comound. |
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Homework Problems 16.1 The empirical formula for an unknown compound is C2H4NO. If the molar mass of the compound is approximately 116 g/mol, what is the molecular formula? 16.2 A compound containing only boron and hydrogen is 88.9% boron by mass. What is the empirical formula for this compound? 16.3. A compound is analyzed and found to contain 68.54% carbon, 8.63% hydrogen, and 22.83% oxygen. The molecular mass of this compound is known to be approximately 140 amu. Determine the empirical formula and molecular formula for the compound. 16.4 Caffeine has the following percent composition: carbon 49.48%, hydrogen 5.19%, oxygen 16.48% and nitrogen 28.85%. Caffeine's molecular mass is 194.19 amu. Determine the empirical and molecular formula for the compound. 16.5 0.1005 g of menthol is combusted, producing 0.2829 g of CO2 and 0.1159 g of H2O. What is menthol's empirical formula? 16.6 A 1.50 g sample of hydrocarbon undergoes complete combustion to produce 4.40 g of CO2 and 2.70 g of H2O. The compound's molecular mass is known to be approximately 75 amu. Determine the empirical formula for the compound.Textbook link HERE. Click and Drag below for answers 16.1 Molecular formula: C4H8N2O2 16.2 B3H4 16.3 Empirical Formula: C4H6O Molecular Formula: C8H12O2 16.4 Empirical Formula: C4H5N2O Molecular Formula: C8H10N4O2 16.5. Empirical Formula: C10H20O 16.6 Empirical Formula: CH3 Molecular Formula: . C5H15 |
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Wednesday January 31, 2024 Day 17 Writing and Balancing Chemical Equations |
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Textbook Readings: 3.11: Writing and Balancing Chemical Equations |
Course Lectures: 3.2 pdf Video* Balancing Chemical Equationss |
| Balancing Chemical Equations: Intro |
Balancing Chemical Equations: Examples |
Objectives: 1. Balance simple chemical equations 2. Balance more complext (Combustion) chemical reaction 3. Interpret balanced chemical reactions in terms of atoms, molecules and moles |
Balancing Chemical Reactions: Fractions |
Homework Problems 17. 1 Balance the following chemical reactions: a. KOH + H3PO4 → K3PO4 + H2O b. NH3 + O2 → NO + H2O c. Al + O2 → Al2O3 d. PCl5 + H2O → H3PO4 + HCl e. FeS + O2 → Fe2O3 + SO2 f. HClO4 + P4O10 → H3PO4 + Cl2O7 g. C6H14 + O2 → CO2 + H2O h. NH2CH2COOH + O2 → CO2 +H2O +N2 17.2 Answer the following questions based upon the combustion reaction for methane: CH4(g) + O2(g) → CO2(g) + H2O(g) a. Is the reaction balanced. If not, balance it. b. What species are considered products? What species are considered reactants? c. Use the balanced chemical reaction to predict how many molecules of O2 must be present to react completely with one molecule of methane. d. Use the balanced chemical reaction to predict how many molecules of O2 must be present to react completely with 525 molecules of methane. e. Use the balanced chemical reaction to predict how many molecules of methane must be present to react completely with 1200 molecules of O2. f. Use the balanced chemical reaction to predict how many molecules of water can be formed from one methane molecule and two O2 molecules. g. Use the balanced chemical reaction to predict how many molecules of carbon dioxide can be formed from 55 methane molecules and 110 O2 molecules. h. Use the balanced chemical reaction to predict how many moles of carbon dioxide can be formed from 55 moles of methane molecules and 110 moles of O2 molecules. i. How many moles of water can be produced when 9.11 x 10-3 moles of CH4 react with just the right amount of O2? Click and Drag below for answers 17. 1 a. 3 KOH + H3PO4 ---> K3PO4 + 3 H2O b.4 NH3 + 5 O2 ---> 4 NO + 6 H2O c.4 Al + 3 O2 ---> 2 Al2O3 d. PCl5 + 4 H2O ---> H3PO4 + 5 HCl e. 4 FeS + 7 O2 ---> 2 Fe2O3 + 4 SO2 f. 12 HClO4 + P4O10 ---> 4 H3PO4 + 6 Cl2O7 g. 2 C6H14 + 19 O2 → 12 CO2 + 14 H2O h. 4 NH2CH2COOH + 9 O2 → 8CO2 + 10 H2O + 2 N2 17.2 a. Here's the balanced reaction: CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(g) b. Products: carbon dioxide and water Reactants: methane and oxygen c. 2 molecules of O2 are required to react with 1 CH4 molecule d. 1050 molecules of O2 are required to react with 525 CH4 molecules e. 600 CH4 molecules are required to react with 1200 O2 molecules f. 2 water molecules will be produced from one methane and two oxygen molecules g. 55 carbon dioxide molecules will be produced from 55 methane and 110 oxygen molecules h. 55 moles of CO2 will be produced from 55 moles of CH4 and 110 moles of O2. i. 1.822 x 10-2 moles of H2O will be produced. |
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| Thursday February 1, 2024 Day 18 More Nomenclature: Acids, Bases and Hydrated Salts |
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| Textbook Readings: 2.1 Chemical Nomenclature |
Course Lectures |
| Naming Acids: Introduction |
Naming Acids: Practice Problems |
| How to remember Strong Acids and Bases |
Nomenclature of Hydrated Salts |
| Objectives 1. Memorize the strong acids 2. Memoize the strong bases 3. Know what a hydrate is, how to write its formula and name. |
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Homework Problems The third
video above also lists weak
acids and weak
bases.
You are not responsible for memorizing them (yet). 18.1 Use the video above and write the names and formulae of the strong acids. Memorize them. 18.2 Use the video above and write the names and formulae of the strong bases. Memorize them. 18.3 What is a hydrated salt and how is it different from an "anhydrate"? How is its formula written? 18.4 What is the correct name for Na2SO3 * 7H2O 18.5 What is the correct name for BeSO4 * 4H2O 18.6 What is the correct name for CuSO4 * 5H2O Click and Drag below for answers 18.1 Check video for answers. 18.2 Check video for answers. 18.3 Check video for answers. 18.4 Check video for answers. 18.5 Check video for answers. 18.6 Check video for answers. |
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| Friday February 2, 2024 Day 19 Reaction Stoichiometry |
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| Textbook Readings: 4.2 Reaction Stoichiometry: How Much Carbon Dioxide? |
Course Lectures 3.3 pdf Video* Calcs. with Chemical Equations |
| Basic Stoichiometry |
Step by Step Stoichiometry |
| Objectives 1. Correctly balance chemical reactions. 2. Write mole ratios using the coefficients from the balanced reaction. 3. Use mole ratios to determine reactant and product mole amounts 4. Use gram/mol conversions and mole ratios to determine reactant and product mole & gram amounts |
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Homework Problems (SHOW ALL WORK FOR CREDIT) 19.1. From the balanced reaction: B2H6 + 3 O2 → 2 HBO2 + 2 H2O a. How many moles of O2 will be needed to produce 4.0 moles of H2O? b. How many moles of B2H6 will be required to react completely with 7.5 moles of O2? c. How many moles of HBO2 will be produced by 2.3 moles of B2H6 and excess O2? 19.2. Given the following balanced reaction: 2 Na2S2O3 + AgBr → NaBr + Na3[Ag(S2O3)2] a. How many moles of Na2S2O3 are needed to react completely with 42.7 grams of AgBr? b. What is the mass of NaBr that will be produced from 42.7 g of AgBr and excess Na2S2O3? 19.3. 10.0 grams pentane (C5H12) was burned with oxygen according to the following balanced reaction: C5H12 + 8 O2 → 5 CO2 + 6 H2O a. How many grams of oxygen were consumed ? b. How many grams of water were formed ? 19.4 35.5 grams of iron oxide are reacted with carbon according to the following UNBALANCED chemical equation. Fe2O3(s) + C(s) → Fe(l) + CO2(g) a. What is the mass of carbon consumed? b. What is the mass of iron produced? c. What is the mass of carbon dioxide produced? d. Conservation of mass requires that the combined product masses must equal the combined reactant masses. Verify that this is true. Click and drag the region below for correct answers. 19.1. a. 6.0 moles O2 required b. 2.5 moles B2H6 c. 4.6 moles HBO2 19.2. a. 0.455 moles Na2S2O3 b. 23.4 grams NaBr 19.3. a. 35.5 grams O2 b. 15.0 grams H2O 19.4 a. 4.00 grams b. 24.8 grams c. 14.7 grams d. 39.5 grams reactant = 39.5 grams product |
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