1. Unit 8 Chemical 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: CHEMICAL CONVERSIONS

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 Old Unit New UnitGiven = Desired Quantity Remember: Multiply the top Divide the bottom

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. 1 dozen apples 12 apples3 dozen apples = 36 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: Na 1+ ) – 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 10 23 (memorize this!) Conversion Factor 1: 1 mole = 6.02 x 10 23 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 10 23 X – You can substitute any item for the X

11. MOLES PARTICLES (atoms, molecules, ions, formula units) 6.02x10 23 1 mole

12. Ex: Convert 1 mole of Fe to number of Fe atoms. Use the factor-label method. mol Fe atoms Fe 1 mol Fe = 6.02 x 10 23 atoms Fe Math: (1) x (6.02 x 10 23 ) / (1) = 6.02 x 10 23 6.02 x 10 23 1 MOLES PARTICLES (atoms, molecules, ions, formula units ) 6.02x10 23 1 mole

13. Ex: Convert 7.8 mol of clipped fingernails to number of clipped fingernails (CF). Use the factor-label method. mol CF CF 7.8 mol CF = 4.7 x 10 24 CF Math: (7.8) x (6.02 x 10 23 ) / (1) = 4.7 x 10 24 6.02 x 10 23 1 MOLES PARTICLES (atoms, molecules, ions, formula units ) 6.02x10 23 1 mole

14. Ex: Convert 2.1 x 10 9 atoms of Li to moles of Li. Use the factor-label method. atoms Li mol Li 2.1 x 10 9 atom Li = 3.49 x 10 -15 mol Li Math: (2.1 x 10 9 ) x (1) / (6.02 x 10 23 ) = 3.49 x 10 -15 1 6.02 x 10 23 MOLES PARTICLES (atoms, molecules, ions, formula units ) 6.02x10 23 1 mole

15. Try the following conversions. 1)1.75 molecules CHCl 3 to mol CHCl 3 2)1.7 x 10 15 mol of H + to ions H + 3)2.80 x 10 24 atoms Si to mol Si 1)2.91 x 10 -24 mol CHCl 3 2)1.0 x 10 39 ions H + 3)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 ElementMoles# of AtomsMassMolar Mass Al1 mol6.02 x 10 23 26.98g26.98 g/mol N1 mol6.02 x 10 23 14.01g14.01 g/mol Pb1 mol6.02 x 10 23 207.2g207.2 g/mol S1 mol6.02 x 10 23 32.07g32.07 g/mol

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 CO 2 = 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 H 2 O? H: 2 x 1.01g = 2.02g O: 1 x 16.00g = 16.00g 18.02 g/mol H 2 O Ex: What is the molar mass of C 6 H 12 O 6 ? 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 C 6 H 12 O 6

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 MOLES PARTICLES (atoms, molecules, ions, formula units ) MM=P.T. 6.02x10 23 1 mole

23. Ex: Convert 2.00 mol Carbon to grams C. Use the factor-label method. mol C 12.01 2.0 mol C = 24.02 g C Math: (2.0) x (12.01) / (1) = 24.02 This is Molar Mass from periodic table 1 mol C = 12.01 g C g C 1 GRAMS MOLES PARTICLES (atoms, molecules, ions, formula units ) MM=P.T. 6.02x10 23 1 mole

24. Ex: Convert 9.73 mol Fe to grams Fe. Use the factor-label method. mol Fe 55.85 9.73 mol Fe = 543 g Fe Math: (9.73) x (55.85) / (1) = 543 This is Molar Mass from periodic table 1 mol Fe = 55.85 g Fe g Fe 1 GRAMS MOLES PARTICLES (atoms, molecules, ions, formula units ) MM=P.T. 6.02x10 23 1 mole

25. Ex: Convert 122 g Al to moles Al. Use the factor-label method. g Al 1 122 g Al = 4.52 mol Al Math: (122) x (1) / (26.98) = 4.52 This is Molar Mass from periodic table 1 mol Al = 26.98 g Al mol Al 26.98 GRAMS MOLES PARTICLES (atoms, molecules, ions, formula units ) MM=P.T. 6.02x10 23 1 mole

26. Ex: Convert 413 g C 6 H 12 O 6 to moles C 6 H 12 O 6. Use the factor-label method. g C 6 H 12 O 6 1 413 g C 6 H 12 O 6 = 2.29 mol C 6 H 12 O 6 Math: (413) x (1) / (180.18) = 2.29 This is Molar Mass from periodic table 1 mol C 6 H 12 O 6 = 180.18 g C 6 H 12 O 6 mol C 6 H 12 O 6 180.18 GRAMS MOLES PARTICLES (atoms, molecules, ions, formula units ) MM=P.T. 6.02x10 23 1 mole

27. Ex: Convert 26 g He to atoms He. Use the factor-label method. g He 1 26 g He = 3.9 x 10 24 atom He Math: (26) x (1) / (4.00) x (6.02 x 10 23 ) / (1) = 3.9 x 10 24 This is Molar Mass from periodic table 1 mol He = 4.00 g He mol He 4.00 GRAMS MOLES PARTICLES (atoms, molecules, ions, formula units ) MM=P.T. 6.02x10 23 1 mole mol He 6.02 x 10 23 atom He 1 This is Avogadro’s Number 1 mol = 6.02 x 10 23 atoms

28. Ex: Convert 345 g CO 2 to molecule CO 2. Use the factor-label method. g CO 2 1 345 g CO 2 = 4.72 x 10 24 molecules CO 2 Math: (345) x (1) / (44.01) x (6.02 x 10 23 ) / (1) = 4.72 x 10 24 This is Molar Mass from periodic table 1 mol CO 2 = 44.01 g CO 2 mol CO 2 44.01 GRAMS MOLES PARTICLES (atoms, molecules, ions, formula units ) MM=P.T. 6.02x10 23 1 mole mol CO 2 6.02 x 10 23 molec CO 2 1 This is Avogadro’s Number 1 mol = 6.02 x 10 23 atoms

29. Try the following. 1)What is the Molar Mass of Platinum (Pt)? 2)Convert: 652.7 g H 2 O to molecules H 2 O 1)195 g/mol 2)2.18 x 10 25 molec. H 2 O GRAMS MOLES PARTICLES (atoms, molecules, ions, formula units ) MM=P.T. 6.02x10 23 1 mole

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) – 0 o C and 1 atm Conversion Factor 5: 1 mole = 22.4 L

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

32. Ex: Convert 5 mol N 2 to liters of N 2. Use the factor-label method. mol N 2 L N 2 5 mol N 2 = 112 L N 2 Math: (5) x (22.4) / (1) = 122 22.4 1

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

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

35. Ex: Convert 49.87 g NH 3 to liters NH 3 at STP. Use the factor-label method. g NH 3 1 49.87 g NH 3 = 65.56 L NH 3 Math: (49.87) x (1) / (17.04) x (22.4) / (1) = 65.56 This is Molar Mass from periodic table 1 mol NH 3 = 17.04 g NH 3 mol NH 3 17.04 mol NH 3 22.4 L NH 3 1 This is Molar Volume at STP 1 mol = 22.4 L

36. Try the following. 1)What is the volume (L) of 589 g N 2 O? 2)Convert: 3.01 x 10 23 molecules of SO 2 to liters. 1)300. L 2)11.2 L H 2 O

37. Chemical Formula The chemical formula can act as a conversion Example: Fe 2 O 3 – The subscripts tell us the number of atoms – 2 atoms of Fe and 3 atoms of O in one formula unit of Fe 2 O 3 – Assume we have 6.02 x 10 23 formula units then… – Fe: 2 x (6.02 x 10 23 atom Fe) = 2 mole Fe – O: 3 x (6.02 x 10 23 atom O) = 3 mole O in 1 mol Fe 2 O 3

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

39. Chemical Formula 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!!! Conversion Factor 3: Chemical Formula (mole to mole)

40. LITERS GRAMS MOLESPARTICLES 6.02x10 23 1 mole Molar Mass Periodic Table 1 mole 22.4 L Chemical Formula

41. Ex: How many mol of N are in 1.00 mol NO 3 ? Use the factor-label method. mol NO 3 1 1.00 mol NO 3 = 1.00 mol N Math: (1.00) x (1) / (1) = 2.00 This is Mole ratio from chemical formula 1 mol NO 3 = 1 mol N mol N 1

42. Ex: How many mol of P are in 1.00 mol P 2 O 5 ? Use the factor-label method. mol P 2 O 5 2 1.00 mol P 2 O 5 = 2.00 mol P Math: (1.00) x (2) / (1) = 2.00 This is Mole Ratio from chemical formula 1 mol P 2 O 5 = 2 mol P mol P 1

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

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

45. Ex: How many grams of O are in 15 mol NO 2 ? Use the factor-label method. mol NO 2 2 15 mol NO 2 = 480 g O Math: (15) x (2) / (1) x (16.00) / (1) = 480 This is Mole Ratio from chemical formula 1 mol NO 2 = 2 mol O mol O 1 16.00 g O 1 This is Molar Mass from periodic table 1 mol O = 16.00 g CO 2

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

47. Try the following. 1)How many moles of acetate are in 2.00 mol Cr(C 2 H 3 O 2 ) 3 ? 2)Convert: 121 g NaOH to grams H. 1)6 mol C 2 H 3 O 2 1- 2)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 mass of sample x 100% (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? % Mg = mass of Mg mass of MgO x 100% = 8.20 g Mg 13.60 g MgO x 100% % Mg = 60.3% Mg % O = mass of O mass of MgO x 100% = 5.40 g O 13.60 g MgO x 100% % O = 39.7% O Note: All percents should add up to about 100%

51. Ex: When 89.1 g H 2 O decomposes, it produces 9.89 g H.What is the % composition? % H = mass of H mass of H 2 O x 100% = 9.89 g H 89.1 g H 2 O x 100% % H = 11.1% H % O = mass of O mass of H 2 O x 100% = (13.60 – 9.89) g O 13.60 g H 2 O x 100% % O = 88.9% O Total mass must equal the sum of its parts: mass H 2 O = mass H + mass O

52. Ex: What is the % composition of C 3 H 8 ? % C = 36.03 g C 44.11 g C 3 H 8 x 100% = 81.68% C % H = 8.08 g H 44.11 g C 3 H 8 x 100% = 18.32% H If we assume 1.00 mol of sample, then we can use periodic table for the mass!!! Mass of C: Mass of H: Mass of C 3 H 8 : 3 mol 12.01 g/mol 8 mol 44.11 g/mol C 3 H 8 1.01 g/molx x= 36.03 g C = 8.08 g H

53. Ex: What is the % composition of (NH 4 ) 2 S? % N = 28.02 g N 68.17 g (NH 4 ) 2 S x 100% = 41.10% N % H = 8.08 g H 68.17 g (NH 4 ) 2 S x 100% = 11.85% H If we assume 1.00 mol of sample, then we can use periodic table for the mass!!! Mass of N: Mass of H: Mass of S: Mass of (NH 4 ) 2 S: 2 mol 14.01 g/mol 8 mol 68.17 g/mol (NH 4 ) 2 S 1.01 g/molx x= 28.02 g N = 8.08 g H % S = 32.07 g S 68.17 g (NH 4 ) 2 S x 100% = 47.04% S 1 mol32.07 g/molx= 32.07 g S

54. Try the following. 1)What is the percent composition of NaOH? 2)What is the percent composition of CH 4 ? 1)57.5% Na 40.0% O 2.5% H 2)75.0% C 25.0% H

55. PART III: EMPIRICAL & MOLECULAR FORMULAS

56. Empirical and Molecular Formulas Each compound has a basic ratio of elements C 6 H 6, C 8 H 8, C 10 H 10  multiples of CH Empirical Formula (EF) – Lowest whole number ratio of elements – Ex: CH, CH 2 O Molecular Formula (MF) – Actual ratio of elements in a compound – Can be the same or whole # multiple of empirical – Ex: C 6 H 6, C 6 H 12 O 6

57. Empirical and Molecular Formulas To determine the empirical, you need % comp – Assume 100g of compound to make math easier To determine the molecular, you need 1.Molar Mass of Compound (Mass Spec) 2.Calculate the Ratio of MF to EF Ratio = Molecular Molar Mass Empirical Molar Mass Molecular Molar Mass is given in the problem.

58. Step to Solve EF/MF Problems

59. Ex: A molecule was determined to be 30.4% N and 69.6% O with a molar mass of 92.02 g/mol. Determine the empirical & molecular formulas.

60. Ex: 40.0% C, 6.67% H, 53.3% O; MM=90.00 g/mol. Determine the empirical & molecular formulas.

61. Ex: A 150g sample consists of 74.25g C, 7.725g H, 43.35g N, and 24.75g O - molar mass of 195 g/mol. Determine the empirical and molecular formulas. Answer: Empirical: C 4 H 5 N 2 O Molecular: C 8 H 10 N 4 O 2

62. Try the following. 1)Find the EF & MF for: 75.69 % C, 8.80% H, 15.51% O with MM = 206 g/mol 1)EF: C 13 H 18 O 2 MF: C 13 H 18 O 2 (Ibuprofen)