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Chemical Quantities

Chemical Quantities. Yeah, Baby!!. Chapter 7. STOP. 2 lb bag of sugar 5 lb bag of potatoes 2 liters of soda-pop 3 gross of M&M’s 10 gallons of gasoline 1 dozen Krispy Kream doughnuts. We describe quantities by weighing them, how much space they take up, or by counting them.

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Chemical Quantities

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  1. Chemical Quantities Yeah, Baby!! Chapter 7

  2. STOP 2 lb bag of sugar 5 lb bag of potatoes 2 liters of soda-pop 3 gross of M&M’s 10 gallons of gasoline 1 dozen Krispy Kream doughnuts • We describe quantities by weighing them, how • much space they take up, or by counting them. • We do the same in chemistry • 2 g of NaCl (weight) • 3 mL of H20 (volume) • 5 moles of MgI (counting)

  3. A mole is a quantity of particles, just as… 1 dozen = 12 things 1 mole = 6.02 x 1023 particles • “Particles” usually measured in moles are atoms, molecules, ions, and formula units

  4. Important # to remember…Avogrado’s Number 1 mole = 6.02 x 1023

  5. Examples: moles  atoms Conversion: 1 mole = 6.02 x 1023 atoms How many atoms of Al are in 1.50 mol of Al? 1 mole 1.50 mol of Al 6.02 x 1023 atoms 9.03 x 1023 atoms of Al =

  6. Examples: moles  molecules  atoms Conversions: 1 mole = 6.02 x 1023 molecules H2O molecule = 2 atoms of Hydrogen How many atoms of H are there in 3.0 moles of H2O? 1 mole 3 moles of H2O 6.02 x 1023 molec. 2 atoms H 1 H2O molecule = 3.6 x 1024 atoms H

  7. Question 1: • Which contains more molecules: • 1.00 mol H2O2 • 1.00 mol C2H6 • 1.00 mol CO • H2O2 • C2H6 • CO • All contains 6.02 x 1023 molecules

  8. Question 2: • Which contains more atoms: • 1.00 mol H2O2 • 1.00 mol C2H6 • 1.00 mol CO • H2O2 • C2H6 • CO • All contains 6.02 x 1023 atoms

  9. Question 3: • Determine the number of atoms in 3.00 mol Sn • 1.81 x 1025 atoms Sn • 1.81 x 1024 atoms Sn • 4.98 x 10-24 atoms Sn • None of the above

  10. 20 Ca 40.08 Molar Mass • Determined simply by looking at the periodic chart • Molar mass = Atomic Mass * Thus, 1 mol Ca = 40 g Molar Mass

  11. Question 4 • Calculate the mass of 1.00 mol of copper • 29 g Cu • 63 g Cu • 64 g Cu • 1 g Cu

  12. Examples: grams  moles Conversion: 1 mole Ag = 108 g Calculate the number of moles in 367 g of silver? 367 g Ag 1 mol Ag 3.40 mol Ag = 108 g Ag

  13. Molar Mass (compound) • Mass of 1 mole in a compound • Determined by adding the molar mass of each atom in that compound What is the gram molecular mass of H2O? 2 atoms H = 1 g x 2 1 atom O = 16 g x 1 = 18 g Thus… 1 mole of H2O = 18 g

  14. Question 5: • Calculate the molar mass of diatomic nitrogen • 7 g N • 14 g N2 • 28 g N2 • 14 g N

  15. Examples: moles  grams Conversion: 1 mole H2O = 18 g What is the mass of 3.40 moles of H2O? 3.4 mol H2O 18 g 61.2 g H2O = 1 mole H2O

  16. Examples: moles  grams Conversion: ammonium carbonate - (NH4)2CO3 N: 2 x 14 g = 28 g H: 8 x 1 g = 8 g C: 1 x 12 g = 12 g O: 3 x 16 g = 48 g What is the mass of 5.60 moles of ammonium carbonate? 1 mol (NH4)2CO3 = 96 g 1 mol (NH4)2CO3 5.60 mol (NH4)2CO3 96 g 538 g =

  17. Examples: moles  atoms Conversions: 1 mole = 6.02 x 1023 molecules 1 (NH4)2CO3 molecule = 14 atoms How many atoms is this? 5.6 moles (NH4)2CO3 14 atoms 1 molecule (NH4)2CO3 6.02 x 1023 molecules 1 mole (NH4)2CO3 = 4.72 x 1025 atoms

  18. When dealing with gasses, volume is determined by using the conversion: 1 mole = 22.4 L

  19. Examples: moles  volume Conversion: 1 mole = 22.4 L How much volume is 5.60 moles of CO2? 1 mol 5.6 mol CO2 22.4 L 125 L CO2 =

  20. STOP Review of conversions for moles 1 mole = 6.02 x 1023particles 1 mole = _____ grams 1 mole = 22.4 L

  21. Examples: Conversion: 1 mole Al = 27 g How many grams of Al are in 2.0 mol Al? 27 g Al 1 mol Al 2.0 mol Al 54 g Al =

  22. 5 mol N2O3 Examples: Conversion: 1 mole N2O3 = 6.02 x 1023 molecules How many molecules are in 5 mol of N2O3? 6.02 x 1023 molecules 1 mol N2O3 = 3.01 x 1024 molecules N2O3

  23. Examples: What is the mass of 8 L of CO2? (Hint: 2 step conversion) Conversion: 1 mol = 22.4 L 1 mol CO2 = 44 g 8 L CO2 1 mol 22.4 L 44 g CO2 1 mol CO2 = 15.7 g CO2

  24. Grams of element in compound Grams of compound Percent Composition: • Describes the relative amounts of each element in a compound (% by mass) % mass of = element x 100

  25. 9.41 15.40 5.99 15.40 What is the % mass of each element when you combine 9.41g of Ca with 5.99g of S ? Grams of Compound = 9.41g + 5.99g = 15.40g % Ca = x 100 = 61% = 39% % S = x 100

  26. 24 30 6 30 x 100 x 100 If you know the chemical formula, you can calculate % composition using molar mass Ex.) Calculate the % comp. of ethane (C2H6) C2 = 24 g H6 = 6 g C2H6 = 30 g % H = % C = % C = 80% % H = 20%

  27. % comp. can be used to calculate the # of grams of an element in a specific amount of a compound Ex.) Calculate the mass of carbon in 30 g of ethane (C2H6) From prev. example: %C in C2H6 = 80% of C .80 (80 %) C 30 gC2H6 x = 24 g C

  28. Empirical Formula • The lowest whole-number ratio of the elements in a compound Ie.) The E.F. of hydrogen peroxide (H2O2) is HO • The E.F. can be determined by % comp.

  29. Ex.) Calculate the formula for a compound that is 67.6% Hg, 10.8% S, & 21.6% O. • Assume you have 100 g of this compound • 67.6 g Hg • 10.8 g S • 21.6 g O • Determine the # of moles of each

  30. 1 mole Hg 200 g Hg 67.6 g Hg .337 mol Hg = 1 mole S 32 g S 10.8 g S .337 mol S = 1 mole O 16 g O 21.6 g O 1.35 mol O = But the subscripts need to be whole #’s

  31. .337 mol Hg .337 mol .337 mol S .337 mol 1.35 mol O .337 mol Empirical Formula • Find the smallest subscript and divide each by it 1 mol Hg = HgSO4 1 mol S = 4 mol O =

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