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Unit 8 The Mole

Unit 8 The Mole. 6.02 X 10 23. The Mole. A counting unit Similar to a dozen, except instead of 12, it’s 602 billion trillion 602,000,000,000,000,000,000,000 Avogadro’s number: 1 mole= 6.02 x 10 23 particles (in scientific notation)

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Unit 8 The Mole

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  1. Unit 8 The Mole 6.02 X 1023

  2. The Mole • A counting unit • Similar to a dozen, except instead of 12, it’s 602 billion trillion 602,000,000,000,000,000,000,000 • Avogadro’s number: 1 mole= 6.02 x 1023 particles(in scientific notation) • This number is named in honor of Amedeo Avogadro (1776 – 1856), who studied quantities of gases and discovered that no matter what the gas was, there were the same number of molecules present

  3. Just How Big is a Mole? • Enough soft drink cans to cover the surface of the earth to a depth of over 200 miles. • If you had Avogadro's number of unpopped popcorn kernels, and spread them across the United States of America, the country would be covered in popcorn to a depth of over 9 miles. • If we were able to count atoms at the rate of 10 million per second, it would take about 2 billion years to count the atoms in one mole.

  4. One mole of $100 bills stacked one on top of another would reach from the Sun to Pluto and back 7.5 milliontimes. One mole of marbles would cover the entire Earth (oceans included) for a depth of three miles.

  5. Homework • How long will it take to spend a mole of Lps.1.00 if they were being spent at a rate of a billion per second?

  6. The Mole • 1 dozen cookies = 12 cookies • 1 mole of cookies = 6.02 X 1023 cookies • 1 dozen cars = 12 cars • 1 mole of cars = 6.02 X 1023 cars • 1 dozen Al atoms = 12 Al atoms • 1 mole of Al atoms = 6.02 X 1023 atoms Note that the NUMBER is always the same, but the MASS is very different! Mole is abbreviated mol (big difference!!)

  7. A Mole of ParticlesContains 6.02 x 1023 particles = 6.02 x 1023 C atoms = 6.02 x 1023H2O molecules = 6.02 x 1023NaCl formula units (ionic compounds are not molecules so they are called formula units) 6.02 x 1023 Na+ ions and 6.02 x 1023Cl– ions 1 mole C 1 mole H2O 1 mole NaCl

  8. Avogadro’s Number as Conversion Factor 6.02 x 1023 particles 1 mole or 1 mole 6.02 x 1023 particles Note that a particle could be an atom, ion, formula unit OR a molecule!

  9. Ex. 1 How many atoms are in 0.67mol of Al? = 0.67 mol Al 6.02x 1023 atoms Al 1 mol Al = 4.0 x 1023 atoms Al Remember to round answer to correct number of significant digits and don’t forget to write units

  10. Ex. 2 A sample of gold contains 5.21 x1023 atoms of gold, how many moles is this? = 5.21x 1023 atoms Au 1 mol Au 6.02x 1023 atoms Au = 0.865 mol Au Remember to round answer to correct number of significant digits and don’t forget to write units

  11. Learning Check 1. Number of atoms in 0.500 mole of Ag a) 500 Ag atoms b) 6.02 x 1023 Ag atoms c) 3.01 x 1023 Agatoms 2.Number of moles of S in 1.8 x 1024 S atoms a) 1.0 mole S atoms b) 3.0 mole S atoms c) 1.1 x 1048 mole S atoms

  12. Learning Check 1. Number of atoms in 0.500 mole of Ag a) 500 Ag atoms b) 6.02 x 1023 Ag atoms c) 3.01 x 1023 Agatoms 2.Number of moles of S in 1.8 x 1024 S atoms a) 1.0 mole S atoms b) 3.0 mole S atoms c) 1.1 x 1048 mole S atoms CW p 323-4 #1-6

  13. Molar Mass • The Mass of 1 mole (in grams) • For atoms: equal to the numerical value of the average atomic mass (get from periodic table, round to the tenth) 1 mole of C atoms = 12.0 g 1 mole of Mg atoms = 24.3 g 1 mole of Cu atoms = 63.5 g • Units: grams/mole or g/mol • Other names for molar mass: • Molecular Mass/Molecular Weight • Formula Mass/Formula Weight

  14. Learning Check! Find the molar mass (usually we round to the tenths place) = 79.9 g/mole • 1 mole of Br atoms • 1 mole of Sn atoms = 118.7 g/mole

  15. Molar Mass of Molecules and Compounds The molar mass of a compound is equal to the sum of the atomic masses of all the atoms in the compound. 1 mole of CaCl2 = 111.1 g/mol 1 mole Ca x 40.1 g/mol = 40.1 g/mol + 2 moles Cl x 35.5 g/mol = 71.0 g/mol = 111.1 g/mol CaCl2

  16. Molar mass for calcium nitrate, Ca(NO3)2 Ca : 1 atom x 40.1 g/mol = 40.1 g/mol N: 2 atoms x 14.0 g/mol = 28.0 g/mol O: 6 atoms x 16.00 g/mol = 96.0 g/mol + 164.1 g/mol

  17. Learning Check! • Molar Mass of K2O = ? Grams/mole B. MolarMass of antacid Al(OH)3 = ? Grams/mole

  18. Learning Check! • Molar Mass of K2O = ? Grams/mole K : 2 x 39.1 = 78.2 O : 1 x 16.0 = 16.0 + 94.2 g/ mol B. MolarMass of antacid Al(OH)3 = ? Grams/mole Al: 1 x 27.0 = 27.0 O: 3 x 16.0 = 48.0 H: 3 x 1.00 = 3.0 + 78.0 g/mol

  19. Learning Check Prozac, C17H18F3NO, is a widely used antidepressant that inhibits the uptake of serotonin by the brain. Find its molar mass. (answer: 304 g/mol) cw p335 #34-36

  20. Calculations with Molar Mass molar mass Grams Moles To convert between grams and moles, use the molar mass of the substance as a conversion factor.

  21. Ex. 1 Aluminum is often used for the structure of light-weight bicycle frames. How many grams of Al are in 3.00 moles of Al? 3.00 moles Al ? g Al To convert between grams and moles, calculate the molar mass of the substance Molar mass of Al 1 mole Al = 27.0 g Al Setup3.00 moles Al x 27.0 g Al 1 mole Al Answer = 81.0 g Al

  22. 2. Acetylsalicylic acid is the chemical name for the substance we commonly know as aspirin, C6H4(OCOCH3)CO2H. How many moles of aspirin are 255g of aspirin? 255 g aspirin ? Mol aspirin • Molar mass of aspirin 1 mole = 180.0 g aspirin • 2. Setup255 g aspirin x 1 mole aspirin • 180 g aspirin • Answer = 1.42 mol aspirin

  23. Learning Check! The artificial sweetener aspartame (Nutra-Sweet) formula C14H18N2O5 is used to sweeten diet foods, coffee and soft drinks. How many moles of aspartame are present in 225 g of aspartame? Answer: 0.765 mol aspartame

  24. Learning Check • A recipe requires 0.629 mol of sucralose, SPLENDA (C12H19Cl3O8). How many grams is this? Answer: 250. g splenda CW: p328-9 #15-18; p336-7 #37-41

  25. Conversions: particles  Grams • 6.02 X 1023 particles = 1 mole AND 1 mole = molar mass (grams) • We can convert between particles and grams (Two step process) • You can’t go directly from atoms to grams!!!! You MUST go thru MOLES.

  26. Calculations : mole road map x Avogadro’s number Mole (mol) ÷Molar mass AVOGADRO’S NUMBER MOLAR MASS (g/mol) Avogadro’s ÷ number Molar mass x Particles (atoms, ions, molecules, formula units) Mass (g)

  27. Atoms/Molecules and Grams Plan: g Cu  mol Cu  atoms Cu How many atoms of Cu are present in 35.4 g of Cu? Step 1: converting g Cu to mol Cu using molar mass 35.4 g Cu 1 mol Cu = 0.5566 mol Cu 63.6 g Cu Step 2: converting mol Cu to atoms Cu using Avogadro’s number. 0.5566 mol Cu 6.02 x 1023 atoms Cu= 3.35x1023 atoms Cu 1 mol Cu

  28. Atoms/Molecules and Grams Plan: g Cu  mol Cu  atoms Cu How many atoms of Cu are present in 35.4 g of Cu? Combining step 1 and 2 35.4 g Cu 1 mol Cu 6.02 x 1023 atoms Cu= 3.35x1023 atoms Cu 63.6 g Cu 1 mol Cu

  29. Atoms/Molecules and Grams Plan: molecules CO mol CO  g CO What is the mass of 5.54x1024 molecules of CO? Step 1: converting molecules CO to mol CO using Avogadro’s number. 5.54x1024molecules of CO 1 mol CO = 9.2026 mol CO 6.02x1023molecules CO Step 2: converting mol CO to g CO using molar mass 9.2026 mol CO 28.0 g CO = 258g CO 1 mol CO

  30. Learning Check! How many atoms of K are present in 78.4 g of K? (answer: 1.21 x 1024 atoms K) 78.4 g K 1 mol K 6.02 x 1023 atoms K= 1.21x1024 atoms K 39.1 g K 1 mol K

  31. Learning Check! What is the mass (in grams) of 1.20 X 1024 molecules of glucose (C6H12O6)? (answer:359 g glucose) 1.20 x 1024 molecules glucose 1 mol glucose 180 g glucose 6.02x1023molecules 1 mol glucose glucose = 359g

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