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Unit 5 CHEMICAL QUANTITIES

Unit 5 CHEMICAL QUANTITIES. CHAPTER 10 – THE MOLE. How much sand?. 3 Ways to Measure Matter. By COUNT – 1 million grains of sand By MASS – 1,000 grams of sand By VOLUME – 100 liters of sand. ATOMIC MASS:. What is the atomic mass of Hydrogen? 1.01 a.m.u.

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Unit 5 CHEMICAL QUANTITIES

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  1. Unit 5CHEMICAL QUANTITIES CHAPTER 10 – THE MOLE

  2. How much sand?

  3. 3 Ways to Measure Matter • By COUNT – 1 million grains of sand • By MASS – 1,000 grams of sand • By VOLUME – 100 liters of sand

  4. ATOMIC MASS: • What is the atomic mass of Hydrogen? • 1.01 a.m.u. • What is the atomic mass of Oxygen? • 15.999  16.0 a.m.u.

  5. The Mass of a Compound = + SO3 1 S atom 3 O atoms You can calculate the mass of a molecule by adding the atomic masses of the atoms making up the molecule. (32.1 + 16 + 16 + 16 = 80.1 amu)

  6. What is the atomic mass of Water (H2O)? • H – 2 (1.0) = 2.0 a.m.u. • O – 1(16.0) =16.0 a.m.u. 18.0 a.m.u • What is the atomic mass of CO2? • C – 1(12.0) = 12.0 a.m.u • O – 2 (16.0) = 32.0 a.m.u. • mass of CO2 = 44.0 a.m.u. • What is the atomic mass of Al2(SO4)3?

  7. What is a MOLE? • A mole is a quantity equal toAvogadro’s Number (6.02 x 1023) • 6.02 x 1023 particles (atoms or molecules) – depending on what you are looking at. • A mole of anything contains the same number of “things” as a mole of anything else. • one mole is set by defining one mole of carbon 12 atoms to have a mass of exactly 12 grams.

  8. Create a Mole “Quantity” Poster • Poster states: “A mole of contains 6.02 x 1023.” • Surrounding that statement is a bunch of pictures depicting your object. • On the back it also states: • “The weight of 1 mole depends on the object” • “If it were a gas, 1 mole would occupy 22.4 liters” Grade based on completeness, creativity, effort, and overall effect.

  9. “Definition” of the molar mass: • Molar Mass = Mass of 1 mole • Weight, in GRAMS, is numerically equal to what its “atomic” weight was in a.m.u.’s • What is the molar mass of Water (H2O)? • 18.0 a.m.u.’s • 18.0 grams / mole • What is the molar mass of CO2? • 44.0 grams / mole

  10. The Mole Road Map Use Molar Mass Use 22.4 L Grams Moles Liters Molecules Use 6.02 x 1023

  11. Practice Problem: • How many moles are in 5.0 g of copper? • 1 mole Cu = 63.5 g • 5.0 g of Cu • Should we have more or less than 1 mole? 5.0 g Cu x 1 mole Cu = 63.5 g Cu 5.0g Cu = .079 moles Cu 63.5 g/mol

  12. How many moles are in 26.0 g of NH3? • 1 mole NH3 = 14.0 + 3.0 = 17.0 g • More or less than 1 mole? • 26.0 g NH3 / 17.0 g/mol = • 1.53 moles NH3

  13. Going the other direction: • How many grams are in 1.5 moles of H2O? • 1 mole H2O = 18.0 g 1.5 mol H2O x 18.0g H2O = 1 mol H2O 27 g H2O 1.5 mol H2O x 18.0 g/mol =

  14. The Mole Road Map Use Molar Mass Use 22.4 L Grams Moles Liters Molecules Use 6.02 x 1023

  15. Volume of a Mole of Gas • The volume of gas varies with temperature and pressure • At Standard temperature and pressure (STP), a mole of ANY gas occupies 22.4L (molar volume) • Standard Temp. = 0 oC • Standard Pressure = 101.3 kpa

  16. Practice Problem: • Sulfur Dioxide (SO2) is a gas produced by burning coal. It is a pollutant that causes acid rain. Determine the volume, in liters, of 0.60 moles of SO2 gas at STP. • At STP, CO2 occupies 36.5L. How many moles of CO2 gas is in the sample?

  17. The Mole Road Map Use Molar Mass Use 22.4 L Grams Moles Liters Molecules Use 6.02 x 1023

  18. Scientific Notation Refresher: • Multiplication: • Multiply Coefficients • Add Exponents • Division: • Divide Coefficients • Subtract Exponents

  19. Practice Problems: • How many molecules are in 1.5 moles of H2O? • 9.03 x 10 23

  20. Going the other direction: • How many moles are in 1.806 x 1024 atoms of Oxygen? • 3 moles

  21. The Mole Road Map Use Molar Mass Use 22.4 L Grams Moles Liters Molecules Use 6.02 x 1023

  22. Tying it all TOGETHER: • How many molecules are in 300g of Na2SO4? • How many grams are in 4.56 x 1023 atoms of Gold (Au)? • What volume, in Liters, would 40g of O2 gas occupy at STP?

  23. Percent Compositionand Chemical Formulas

  24. Percent Composition = • the percent by mass of each element in a compound. Mass of element % mass of element = x 100% Mass of compound

  25. Percent Composition • Calculate the formula mass of C2H3O2? • What percent of this compound is oxygen by mass? Mass of element % mass of element = x 100% Mass of compound 32.0g x 100% = 54.2% 59.0g

  26. Sample Problem: 9.03 g Mg combine completely with 3.48 g N to form a compound. What is the percent composition of this compound? (9.03 g + 3.48 g = 12.51 g) % Mg = mass of Mg x 100 = 9.03 g x 100 = 72.2% Mg mass of compound 12.51 g % N = mass of N x 100 = 3.48 g x 100 = 27.8 % N mass of compound 12.51 g

  27. Practice Problem: • Propane, C3H8, is commonly used in gas grills. Calculate the percent composition of this compound.

  28. Calculating Empirical Formulas • Empirical Formula = the lowest whole-number ratio of atoms of the elements in a compound. • may or may not be the same as a molecular formula.

  29. Hydrogen Peroxide H2O2 = molecular formula HO = empirical formula Carbon Dioxide CO2 = molecular formula CO2 = empirical formula

  30. Calculating Molecular Formulas: • The molecular formula of a compound can be determined if you know its empirical formula and its molar mass.

  31. Example: • Calculate the molecular formula of the compound whose molar mass is 60.0 g and empirical formula is CH4N. • First calculate the empirical formula mass. • Then divide the empirical formula mass into the molar mass. • Multiply formula subscripts by this value to get the molecular formula.

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