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Chapter 7

Chapter 7. Representative particle- refers to whether a substance commonly exists as atoms, ions, or molecules Ex. Elements- Representative Particle is the atom. 7 elements exist as diatomic molecules H 2 N 2 O 2 F 2 Cl 2 Br 2 I 2

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Chapter 7

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  1. Chapter 7

  2. Representative particle- refers to whether a substance commonly exists as atoms, ions, or molecules • Ex. Elements- Representative Particle is the atom

  3. 7 elements exist as diatomic molecules • H2 N2 O2 F2 Cl2 Br2 I2 • Representative Particle of a molecular compound is a molecule Example CO SO3

  4. Formula unit (FU) • Representative Particle of ionic compounds • Example • NaCl AgNO3 BaS Ca(C2H3O2)2

  5. Mole- Chemists quantity of a substance that represents 6.02x1023 representative particles of that substance- called Avagadro’s number • ex. 1 dozen eggs • How many moles of Mg atoms in 3.01x1022 atoms of Mg? • # of moles in 1.20x1025 atoms of P?

  6. # of atoms in .750 mol of Zn? • # of molecules in 4 mol of glucose, C6H12O6? • # of moles in 1.20x1024 molecules of CO2 ?

  7. To find the # of atoms in 1 mole of a compound, you must determine the # of atoms in a representative formula of that compound

  8. # of fluoride ions in 1.46 mol of Aluminum fluoride? • # of C atoms in a mixture of 3 mol C2H2 and .7 mol carbon monoxide?

  9. Atomic Mass – amu • Mass of single atom • Ex) C = 12 amu • Ex) H = 1 amu (Periodic Table)

  10. Gram Atomic Mass – gam • # of grams of an element that is numerically equal to the atomic mass in amu. • Ex) Carbon – gam is 12 g • Ex) Oxygen – gam is 16 g

  11. GAM – mass of 1 mol of atoms of a mono-atomic element • Ex) Carbon – gam is 12 g/mol • Ex) Oxygen – gam is 16 g/mol

  12. GMM – mass of 1 mol of that compound. • Ex) GMM of H2O2

  13. 2 mol H x 1 g H = 2.0 g H 1 mol H 2 mol O x 16.0 g O = 32.0 g O 1 mol O 34 g

  14. Examples • Find the GMM of C6H4Cl2

  15. C 6 x 12.01 = 72.06 • H 4 x 1 = 4 • Cl 2 x 35.45 = 70.9 146.96 g

  16. GFM – Mass of 1 mol of an ionic compound. • Ex) GFM of Ammonium Carbonate

  17. 2 mol N x 14gN = 28 g 1 mol N 8 mol H x 1 g H = 8 g 1 mol H 1 mol C x 12 g C = 12 g 1 mol C 3 mol O x 16 g O = 48 g 1 mol O 96 g

  18. Molar Mass • Mass of a mole of any element or compound. • Ex) O2 = 32 g/mol, • O = 16 g/mol

  19. Mole Mass Conversion • Ex) # of grams in 7.20 mole of dinitrogen trioxide

  20. 2 mol N x 14 g N = 28 g N 1 mol N 3 mol O x 16 g O = 48 g O 1 mol O 76 g

  21. Example Cont’d… 7.20 mol N2O3 x 76 g N2O3 1mol N2O3 = 5.47 x 102 g N2O3

  22. Grams Moles • Ex) find # of moles 922g of iron(III) oxide.

  23. 922 g Fe2O3 x 1 mol Fe2O3 159.6 g Fe2O3 = 5.78 mol Fe2O3

  24. The Volume of a gas at Standard Temperature and Pressure is 22.4 L (STP). • Std Temp = 0°C • Std Press = 1 atmosphere (atm) • 22.4 = molar volume of a gas = 22.4 L 1 mol

  25. Ex) Determine the Volume in L of 0.600 mol of Sulfur Dioxide gas @ STP. • Mol L • Known : 1 mol SO2 = 22.4 L

  26. .600 mol SO2 x 22.4 L 1 mol SO2 = 13.4 L SO2

  27. Gas Density and Gram Molecular Mass • Density of gas – units g/L • Ex. Density of carbon and oxygen is 1.969 g/L at STP. Determine gfm. Is compound CO or CO2 ? • Densities of A, B, and C are 1.25, 2.86, and .714 g/L at STP. Calculate gfm of each. Identify each substance as ammonia, sulfur dioxide, chlorine, nitrogen or methane.

  28. Volume of gas at STP Representative particles 1 mol/6.02x1023 part 1 mol/ 22.4 L 22.4 L/ 1 mol 6.02x1023 part/ 1 mol Mole 1 mol/gfm gfm/ 1 mol Mass

  29. Ex. How many Carbon atoms are in a 50 carat diamond that is pure carbon? • 50 carats= 10 g • Mass in grams of an atom of nickel? • How many molecules are in a 6 L balloon filled with carbon dioxide (@ STP)?

  30. Percent Composition • the percent by mass of each element in a compound.

  31. Examples • Find the percent composition of K2CrO4

  32. % mass = grams of element x 100 grams of compound

  33. 40.3 % K • 26.8 % Cr • 32.9 % O • They must add up to equal 100%

  34. Example • An 8.20g piece of Mg combines completely with 5.40g of oxygen to form a compound. Calculate the % composition of the compound.

  35. 8.20g + 5.40g = 13.60g % Mg = mass of Mg x 100 mass of compound 8.2 x 100 = 60.3% 13.6

  36. Cont’d %O = mass of O x 100 mass of compound = 5.40 x 100 = 39.7% 13.6

  37. Example • 29g of silver combines with 4.3g of sulfur. Calculate % composition.

  38. 29 x 100 = 87.1% Ag 33.3 4.3 x 100 = 12.9%S 33.3

  39. Example • 222.6g of Sodium combines with 77.4g of Oxygen. Calculate % composition.

  40. 222.6 x 100 = 74.2 % Na 300 77.4 x 100 = 25.8% O 300

  41. % Composition of a known compound % mass = grams of element in 1 mol of cmpd x 100 gfm of compound

  42. Examples • Calculate the % composition of ethane, C2H6.

  43. Cont’d • C - 2 x 12 = 24g • H - 6 x 1 = 6g 30 g

  44. Cont’d 24 x 100 = 80 % C 30 6 x 100 = 20 % H 30

  45. Examples • Calculate the % composition of: • a) C3H8 • b) Calcium Acetate • c) Hydrogen Cyanide

  46. a) 81.8%C, 18.2% H • b) 25.4% Ca, 30.4% C, 3.8% H, 40.5% O • c) 3.7% H, 44.4% C, 51.9% N

  47. Examples • Calculate the mass of Carbon in 82 g of C2H6.

  48. 82g C2H6 x 80g C = 66g C 100g C2H6 *Based on previous example, Composition of C in C2H6 is 80% C & 20% H

  49. Examples • Calculate the amount of Hydrogen in the following compounds.

  50. 350 g C3H8 350 g C3H8 x 18.2g H = 100g C3H8 63.7g H

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