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The mole, Avogadro’s number, and Molar Mass

The mole, Avogadro’s number, and Molar Mass. The Mole. How many items are in a dozen? 12 How many “items” are in a mole? 6.022 x 10 23 molecules, atoms, or some other unit. Represents a much larger number than 12. How big is a mole?.

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The mole, Avogadro’s number, and Molar Mass

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  1. The mole, Avogadro’s number, and Molar Mass

  2. The Mole • How many items are in a dozen? • 12 • How many “items” are in a mole? • 6.022 x 1023 molecules, atoms, or some other unit. • Represents a much larger number than 12

  3. How big is a mole? • One mole represents a set of 602,200,000,000,000,000,000,000 items!!! • Just as a dozen eggs represent 12 eggs, a mole of carbon items represents 602,200,000,000,000,000,000,000 carbon items.

  4. Avogadro’s Number • 6.022 x 1023 • The number of particles in exactly one mole of a pure substance

  5. Molar Mass • The mass of one mole of a pure substance • NOT the atomic mass! • Atomic mass is the mass of one atom • Molar mass is the mass of one mole of particles! • However, the molar mass is numerically equal to the atomic mass of the element in atomic mass units (amu). • Expressed in grams/mole (or g/mol)

  6. Gram/Mole Conversions • The molar mass of helium is 4.00 g He/mol He. To find how many grams of He there are in two moles of helium, multiply by the molar mass. • 2.00 mol He X 4.00 g He = 8.00 g He 1 mol He

  7. Sample Problem B (pg 84) What is the mass in grams of 3.50 mol of the element copper, Cu? • Given: 3.50 mol Cu • Unknown: mass of Cu in grams • moles Cu X grams Cu = grams Cu moles Cu 3.50 mol Cu X 63.55 g Cu = 222 g Cu 1 mol Cu

  8. Sample Problem C (pg 85) • A chemist produced 11.9 grams of Aluminum, Al. How many moles of aluminum were produced? • Given: 11.9 g Al • Unknown: amount of Al in moles • 11.9 g Al X 1 mol Al = 0.441 mol Al 26.98 g Al

  9. Moles/Atoms Conversions • Avogadro’s number can be used to find the number of atoms in an element from the amount of moles.

  10. Sample Problem D (pg 86) • How many moles of silver, Ag, are in 3.01 x 1023 atoms of silver? • Given: 3.01 x 1023 atoms of Ag • Unknown: amount of Ag in moles • 3.01 x 1023 Ag atoms X 1 mol Ag = 0.500 mol Ag 6.022 x 1023 Ag atoms

  11. Sample Problem E (pg 86) • How do we convert atoms to grams? • What is the mass in grams of 1.20 x 108atoms of copper, Cu? • Given: 1.20 x 108atoms of Cu • Unknown: mass of Cu number of atoms  amount of Cu in moles  mass of Cu in grams • 1.20 x 108 Cu atoms x 1 mol Cu x 63.55 g Cu = 6.022 x 1023 Cu atoms 1 mol Cu

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