Homework 6 (Chapter 3)-solutions

# Homework 6 (Chapter 3)-solutions - wolf(bw7658 – Homework...

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Unformatted text preview: wolf (bw7658) – Homework 6 (Chapter 3) – sutcliffe – (50965) 1 This print-out should have 20 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. This homework is entirely on Chapter 3 to give you some Quest practice on moles, grams and stoichiometry. 001 10.0 points Avogadro’s number is really big. If you had 6.02 × 10 23 dollars, and could spend it at \$1 billion (10 9 ) per second for the rest of your life (let’s say 80 years), approximately what percentage of your original money would you have left when you die? 1. 75% 2. 10% 3. 0% 4. 90% 5. 95% 6. 100% correct 7. 50% Explanation: 002 10.0 points Which one has the greatest number of atoms? 1. All have the same number of atoms 2. 3.05 moles of water 3. 3.05 moles of helium 4. 3.05 moles of CH 4 correct 5. 3.05 moles of argon Explanation: For 3.05 moles of water: ? atoms = 3 . 05 mol H 2 O × 6 . 02 × 10 23 molec 1 mol × 3 atoms 1 molecule = 5 . 51 × 10 24 atoms For 3.05 moles of CH 4 : ? atoms = 3 . 05 mol CH 4 × 6 . 02 × 10 23 molec 1 mol × 5 atoms 1 molecule = 9 . 18 × 10 24 atoms For 3.05 moles of helium: ? atoms = 3 . 05 mol He × 6 . 02 × 10 23 atoms 1 mol = 1 . 84 × 10 24 atoms For 3.5 moles of argon: ? atoms = 3 . 05 mol Ar × 6 . 02 × 10 23 atoms 1 mol = 1 . 84 × 10 24 atoms 003 10.0 points If one electron weighs 9 . × 10 − 28 grams, what is the mass of one mole of electrons? 1. 1 . 5 × 10 − 51 grams 2. 9 . × 10 − 18 grams 3. 5 . × 10 − 23 grams 4. 5 . 4 × 10 − 4 grams correct 5. 5 . × 10 − 24 grams Explanation: m = 9 . × 10 − 28 g We know one mole of electrons contains 6 . 022 × 10 23 electrons. Since we know the mass of an individual electron we can calcu- late the mass of one mole of electrons. ? g/mol e − = 9 . × 10 − 28 g 1 e − × 6 . 022 × 10 23 e − 1 mol e − = 5 . 4 × 10 − 4 g/mol e − wolf (bw7658) – Homework 6 (Chapter 3) – sutcliffe – (50965) 2 004 10.0 points What is the molar mass for fluoxetine (C 16 H 16 F 3 NO), also known as Prozac circlecopyrt R ? 1. 279.3 g/mol 2. 295.3 g/mol correct 3. 297.1 g/mol 4. 281.3 g/mol Explanation: MM C 16 H 16 F 3 NO = 16(12 . 011 g / mol) +16(1 . 0079 g / mol) + 3(18 . 9984 g / mol) +1(14 . 0067 g / mol) + 1(15 . 9994 g / mol) = 295 . 304 g / mol 005 10.0 points Calculate the density of propanol C 3 H 8 O if you know that there are 1 . 069 × 10 25 molecules of propanol in 1.35 L. 1. 0.789 g/mL correct 2. 1.23 g/mL 3. 13.1 g/mL 4. 1.27 g/mL 5. 0.234 g/mL 6. 0.0131 g/mL Explanation: n = 1 . 069 × 10 25 molec V = 1 . 35 L Density is g/mL, so we need to convert molecules propanol to g propanol and L to mL: ? g mL = 1 . 069 × 10 25 molec C 3 H 8 O 1 . 35 mL × 1 mol C 3 H 8 O 6 . 023 × 10 23 molec C 3 H 8 O × 60 g C 3 H 8 O 1 mol C 3 H 8 O × 1 L 1000 mL = 0 . 789 g / mL 006 10.0 points Calculate the number of ethanol molecules (CH 3 CH 2 OH) that would contain 164 grams of carbon....
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Homework 6 (Chapter 3)-solutions - wolf(bw7658 – Homework...

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