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Unit 8 Chemical Quantities

Unit 8 Chemical Quantities. Chemistry I Mr. Patel SWHS. Topic Outline. MUST have a scientific calculator (not graphing)!!! Review of Factor-label Method The Mole: Particle to Mole Conversion (10.1) Molar Mass: Gram to Mole Conversion (10.2)

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Unit 8 Chemical Quantities

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  1. Unit 8Chemical Quantities Chemistry I Mr. Patel SWHS

  2. Topic Outline • MUST have a scientific calculator (not graphing)!!! • Review of Factor-label Method • The Mole: Particle to Mole Conversion (10.1) • Molar Mass: Gram to Mole Conversion (10.2) • Molar Volume: Volume to Mole Conversion (10.2) • Chemical Formula as a Conversion Factor (N/A) • Percent Composition (10.3) • Empirical and Molecular Formulas (10.3) • Solution Concentration (16.2)

  3. Part I:chemicalconversions

  4. Conversion Factors • Conversion factor – allows us to convert from one unit to another unit • Example: 1m = 1000mm, 1 dozen = 12 items • We use the factor label method to convert Given New Unit Remember: Multiply the top Divide the bottom DesiredQuantity = Old Unit

  5. Measuring by Count • A count refers to a grouping or a word representing a number • Pair (2), Dozen (12), Ream (500) • A count is a conversion factor – can convert between a count unit and the number of items • Ex: 1 dozen egg is the same as 12 actual eggs

  6. Ex: Convert 3 dozen apples to number of apples. Use the factor-label method. 3 dozen apples 12 apples = 36 apples 1 dozen apples

  7. Representative Particle • Representative Particle – species present in a substance • Atoms (elements; ex: Fe atom) • Molecules (covalent compounds; ex: diatomics) • Ions (species with a charge; ex: Na1+) • Formula Units (ionic compounds; ex: NaCl)

  8. The Mole • The fundamental count in chemistry is the mole – SI unit for amount • Very similar to a dozen; represents a number • Abbreviation: mol • Contains an Avogadro’s Number of items • Avogadro’s Number = 6.02 x 1023(memorize this!) • Conversion Factor 1: 1 mole = 6.02 x 1023 items

  9. The Mole • It is not appropriate to consider only one atom of an element or one formula unit of a compound • It is easier to group atoms using a large number • NOTE: 1 mole contains the same number of item…but does not necessarily have the same mass!!!

  10. The Mole • Just like a dozen, the mole is a conversion factor! • We can convert between the unit (mole) and the number of items • Remember: • 1 mole X = 6.02 x 1023X • You can substitute any item for the X

  11. MOLES 1 mole 6.02x1023 PARTICLES (atoms, molecules,ions, formula units)

  12. Ex: Convert 1 mole of Fe to number of Fe atoms. Use the factor-label method. MOLES 6.02 x 1023 atoms Fe 1 mol Fe = 6.02 x 1023 atoms Fe 1 mole 1 6.02x1023 mol Fe PARTICLES (atoms, molecules, ions, formula units ) Math: (1) x (6.02 x 1023) / (1) = 6.02 x 1023

  13. Ex: Convert 7.8 mol of clipped fingernails to number of clipped fingernails (CF). Use the factor-label method. MOLES 6.02 x 1023 CF 7.8 mol CF = 4.7 x 1024 CF 1 mole 6.02x1023 1 mol CF PARTICLES (atoms, molecules, ions, formula units ) Math: (7.8) x (6.02 x 1023) / (1) = 4.7 x 1024

  14. Ex: Convert 2.1 x 109 atoms of Li to moles of Li. Use the factor-label method. MOLES 1 mol Li 2.1 x 109 atom Li = 3.49 x 10-15 mol Li 6.02 x 1023 1 mole 6.02x1023 atoms Li PARTICLES (atoms, molecules, ions, formula units ) Math: (2.1 x 109) x (1) / (6.02 x 1023) = 3.49 x 10-15

  15. Try the following conversions. • 1.75 molecules CHCl3to mol CHCl3 • 1.7 x 1015 mol of H+to ions H+ • 2.80 x 1024 atoms Si to mol Si • 2.91 x 10-24 mol CHCl3 • 1.0 x 1039ions H+ • 4.65 mol Si

  16. Mass of an Element • On the periodic table, the mass of an element is given in units of atomic mass unit • 1/12 the mass of a carbon-12 atom • In the laboratory, we do not use amu. We measure chemicals in grams. • We can treat the amu as “grams per mole”. • Carbon: 12 amu 12 grams in 1 mole

  17. Mole-Atom-Mass Relationship

  18. Molar Mass (MM) • The mass of one mole of an element of compound • Units: grams/mole (g/mol) • Can be called Molecular Weight (MW) • For element, MM comes directly from mass on PT • For compound, add the mass of each atom • CO2 = Add (mass of C) and 2 x (mass of O) • Conversion Factor 2: 1 mole = Mass in Grams (from PT)

  19. Ex: What is the molar mass of iron? 55.85 g/mol Fe (from Periodic Table) Ex: What is the molar mass of boron? 10.81 g/mol B (from Periodic Table)

  20. Ex: What is the molar mass of H2O? H: 2 x 1.01g = 2.02g O: 1 x 16.00g = 16.00g 18.02 g/mol H2O Ex: What is the molar mass of C6H12O6? C: 6 x 12.01g = 72.06g H: 12 x 1.01g = 12.12g O: 6 x 16.00g = 96.00g 180.18 g/mol C6H12O6

  21. Molar Mass Conversions • The molar mass is a conversion between the mole and grams. • Moles are used in theory • Grams are used in lab/practice • Molar Mass allows: mole  grams • Using 2 conversion factors: particle  grams • We must go through the mole!!!

  22. GRAMS 1 mole MM=P.T. MOLES 1 mole 6.02x1023 PARTICLES (atoms, molecules,ions, formula units )

  23. GRAMS This is Molar Massfrom periodic table 1 mol C = 12.01 g C Ex: Convert 2.00 mol Carbon to grams C. Use the factor-label method. 1 mole MM=P.T. MOLES 12.01 g C 2.0 mol C = 24.02 g C 1 mole 6.02x1023 1 mol C PARTICLES (atoms, molecules, ions, formula units ) Math: (2.0) x (12.01) / (1) = 24.02

  24. GRAMS This is Molar Massfrom periodic table 1 mol Fe = 55.85 g Fe Ex: Convert 9.73 mol Fe to grams Fe. Use the factor-label method. 1 mole MM=P.T. MOLES 55.85 g Fe 9.73 mol Fe = 543 g Fe 1 mole 6.02x1023 1 mol Fe PARTICLES (atoms, molecules, ions, formula units ) Math: (9.73) x (55.85) / (1) = 543

  25. GRAMS This is Molar Massfrom periodic table 1 mol Al = 26.98 g Al Ex: Convert 122 g Al to moles Al. Use the factor-label method. 1 mole MM=P.T. MOLES 1 mol Al 122 g Al = 4.52 mol Al 1 mole 6.02x1023 g Al 26.98 PARTICLES (atoms, molecules, ions, formula units ) Math: (122) x (1) / (26.98) = 4.52

  26. GRAMS This is Molar Massfrom periodic table 1 mol C6H12O6 = 180.18 g C6H12O6 Ex: Convert 413 g C6H12O6 to moles C6H12O6. Use the factor-label method. 1 mole MM=P.T. MOLES 1 mol C6H12O6 413 g C6H12O6 = 2.29 mol C6H12O6 1 mole 6.02x1023 g C6H12O6 180.18 PARTICLES (atoms, molecules, ions, formula units ) Math: (413) x (1) / (180.18) = 2.29

  27. GRAMS This is Molar Massfrom periodic table 1 mol He = 4.00 g He This is Avogadro’s Number 1 mol = 6.02 x 1023 atoms Ex: Convert 26 g He to atoms He. Use the factor-label method. 1 mole MM=P.T. MOLES 1 mol He 6.02 x 1023 atom He 26 g He = 3.9 x 1024 atom He 1 mole g He 6.02x1023 mol He 1 4.00 PARTICLES (atoms, molecules, ions, formula units ) Math: (26) x (1) / (4.00) x (6.02 x 1023) / (1) = 3.9 x 1024

  28. GRAMS This is Molar Massfrom periodic table 1 mol CO2 = 44.01 g CO2 This is Avogadro’s Number 1 mol = 6.02 x 1023 atoms Ex: Convert 345 g CO2 to molecule CO2. Use the factor-label method. 1 mole MM=P.T. MOLES molec CO2 1 mol CO2 6.02 x 1023 345 g CO2 = 4.72 x 1024molecules CO2 1 mole g CO2 6.02x1023 mol CO2 1 44.01 PARTICLES (atoms, molecules, ions, formula units ) Math: (345) x (1) / (44.01) x (6.02 x 1023) / (1) = 4.72 x 1024

  29. Try the following. GRAMS • What is the Molar Mass of Platinum (Pt)? • Convert: 652.7 g H2O to molecules H2O • 195 g/mol • 2.18 x 1025 molec. H2O 1 mole MM=P.T. MOLES 1 mole 6.02x1023 PARTICLES (atoms, molecules, ions, formula units )

  30. Mole to Volume Conversion • Gases are often measured in volume rather than grams • A conversion is available between mole and volume only at specific conditions • Only for gases (ideal) • Standard Temperature and Pressure (STP) • 0oC and 1 atm • Conversion Factor 5: 1 mole = 22.4 L

  31. 1 mole MOLES PARTICLES 1 mole Avogadro Number LITERS Molar Volume 1 mole (atoms, molecules, ions, formula units) Molar Mass GRAMS

  32. Ex: Convert 5 mol N2 to liters of N2. Use the factor-label method. 22.4 L N2 5 mol N2 = 112 L N2 1 mol N2 Math: (5) x (22.4) / (1) = 122

  33. Ex: Convert 12.5 mol Ar to liters of Ar. Use the factor-label method. 22.4 L Ar 12.5 mol Ar = 280 L Ar 1 mol Ar Math: (12.5) x (22.4) / (1) = 280

  34. Ex: Convert 69.8 L Ne to mol of Ne. Use the factor-label method. 1 mol Ne 69.8 L Ne = 3.17 mol Ne 22.4 L Ne Math: (69.8) x (1) / (22.4) = 3.17

  35. This is Molar Massfrom periodic table 1 mol NH3 = 17.04 g NH3 This is Molar Volume at STP1 mol = 22.4 L Ex: Convert 49.87 g NH3 to liters NH3 at STP. Use the factor-label method. L NH3 1 mol NH3 22.4 49.87 g NH3 = 65.56L NH3 g NH3 mol NH3 1 17.04 Math: (49.87) x (1) / (17.04) x (22.4) / (1) = 65.56

  36. Try the following. • What is the volume (L) of 589 g N2O? • Convert: 3.01 x 1023 molecules of SO2 to liters. • 300. L • 11.2 L H2O

  37. Chemical Formula • The chemical formula can act as a conversion • Example: Fe2O3 • The subscripts tell us the number of atoms • 2 atoms of Fe and 3 atoms of O in one formula unit of Fe2O3 • Assume we have 6.02 x 1023 formula units then… • Fe: 2 x (6.02 x 1023 atom Fe) = 2 mole Fe • O: 3 x (6.02 x 1023 atom O) = 3 mole O in 1 mol Fe2O3

  38. Chemical Formula • The chemical formula is a mole ratio!!! • If we have 1 mole C6H12O6 then… 1 mol C6H12O6 : 6 mol C : 12 mol H : 6 mol O Colon (:) means chemically equivalent • Conversion Factor 3: Chemical Formula (mole to mole)

  39. Chemical Formula • Conversion Factor 3: Chemical Formula (mole to mole) • NOTE!!! When you are changing from one chemical to another, you must do this through the mole stage! • Mole X  Mole Y • This is strictly a mole to mole conversion. • NOT GRAMS!!!

  40. Chemical Formula 1 mole MOLES PARTICLES 1 mole LITERS 6.02x1023 22.4 L 1 mole Molar Mass Periodic Table GRAMS

  41. This is Mole ratiofrom chemical formula 1 mol NO3 = 1 mol N Ex: How many mol of N are in 1.00 mol NO3? Use the factor-label method. 1 mol N 1.00 mol NO3 = 1.00 mol N 1 mol NO3 Math: (1.00) x (1) / (1) = 2.00

  42. This is Mole Ratiofrom chemical formula 1 mol P2O5 = 2 mol P Ex: How many mol of P are in 1.00 mol P2O5? Use the factor-label method. 2 mol P 1.00 mol P2O5 = 2.00 mol P 1 mol P2O5 Math: (1.00) x (2) / (1) = 2.00

  43. This is Mole Ratiofrom chemical formula 1 mol Pb2S3 = 3 mol S Ex: How many mol of S are in 6.80 mol Pb2S3? Use the factor-label method. 3 mol S 6.80 mol Pb2S3 = 20.4 mol S 1 mol Pb2S3 Math: (1.00) x (2) / (1) = 2.00

  44. This is Mole Ratiofrom chemical formula 1 mol CHCl3 = 3 mol Cl This is Molar Massfrom periodic table 1 mol Cl = 35.45 g Cl Ex: How many grams of Cl are in 8.00 mol CHCl3? Use the factor-label method. g Cl 3 mol Cl 35.45 8.00 mol CHCl3 = 851 g Cl mol CHCl3 mol Cl 1 1 Math: (8.00) x (3) / (1) x (35.45) / (1) = 851

  45. This is Mole Ratiofrom chemical formula 1 mol NO2 = 2 mol O This is Molar Massfrom periodic table 1 mol O = 16.00 g CO2 Ex: How many grams of O are in 15 mol NO2? Use the factor-label method. g O 2 mol O 16.00 15 mol NO2 = 480 g O mol NO2 mol O 1 1 Math: (15) x (2) / (1) x (16.00) / (1) = 480

  46. This is Molar Massfrom periodic table 1 mol XeF6 = 245.29 g XeF6 This is Mole Ratiofrom chemical formula 1 mol XeF6 = 6 mol F This is Molar Massfrom periodic table 1 mol F = 19.00 g F Ex: How many grams of F are in 10.2 g XeF6? Use the factor-label method. mol F 1 mol XeF6 6 g F 19.00 10.2 g XeF6 = 4.74 g F 1 mol F g XeF6 mol XeF6 1 245.29 Math: (10.2) x (1) / (245.29) x (6) / (1) x (19.00) / (1) = 4.74

  47. Try the following. • How many moles of acetate are in 2.00 mol Cr(C2H3O2)3? • Convert: 121 g NaOHto grams H. • 6 mol C2H3O21- • 3.03 g H

  48. Part II:Percent Composition

  49. Percent Composition • Describes the relative amounts of each element in a compound • The percent composition is always the same - no matter the quantity of the sample • Also called “Percent by Mass” % X mass of X 100% x = mass of sample (X represents some element found in the sample)

  50. Ex: When 13.60 g sample of MgO decomposes, it produces 8.20 g Mg and 5.40 g O. What is the % composition? mass of Mg 8.20 g Mg % Mg 100% 100% x x = = mass of MgO 13.60 g MgO % Mg 60.3% Mg = mass of O 5.40 g O % O 100% 100% x x = = mass of MgO 13.60 g MgO % O 39.7% O = Note: All percents should add up to about 100%

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