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Chapter 11 Notes, Part I

Chapter 11 Notes, Part I. What is a mole? One Step Problems. What is a mole?. A furry, burrowing woodland creature, revered by many and adored by all?. Maybe!. But not really in chemistry!. A Mole. is a unit of measurement that tells how many particles of something you have!.

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Chapter 11 Notes, Part I

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  1. Chapter 11 Notes, Part I What is a mole? One Step Problems

  2. What is a mole? • A furry, burrowing woodland creature, revered by many and adored by all? Maybe! • But not really in chemistry!

  3. A Mole... • is a unit of measurement that tells how many particles of something you have!

  4. much like a dozen (12), a gross (144) or a ream (500) is just a unit that groups smaller numbers into big ones...but its a big one; a REALLY big one!

  5. 1 mole = 6.02 x 1023 particles! (that’s a lot of flowers!)

  6. What are particles? • Particles could be anything, but because of the size of the number, we usually mean Atoms, molecules, or formula units.

  7. Avogadro’s Number • The number 6.02 x 1023 is called Avogadro’s number. • This is due to Amadeo Avagadro’s research leading to the discovery, not the discovery of the number itself. It is a little known fact that Avogadro was voted his class’s most likely to have a scientific discovery and most likely to look really creepy.

  8. Practice Problem #1 • How many moles are in 2.57 x 1025 atoms He?

  9. Practice Problem #2 • How many molecules of CO2 are in 25.3 moles?

  10. Two Step Problems (the mole road) • We have now discussed moles in two ways—as particles (1 mol = 6.02x1023 particles), and as a mass ( molar mass = 1 mol) • To get from particles to grams, grams to moles of a substance, two steps are required, with moles always in between!

  11. The Mole Road

  12. Mass and Moles • How do we usually measure out chemicals in a lab? NOT by counting the number of particles!

  13. Mass and Moles • We usually use mass to measure out chemicals. • The problem with mass is that not all atoms or compounds have the same mass.

  14. Mass and Moles • Avogadro’s number was established by using Carbon-12 as a standard. The number of particles in 12 grams of carbon 12 was set as 1 mole.

  15. Mass and Moles • Conveniently, this is similar to how the atomic mass unit was established, so the atomic mass on the periodic table is also an element’s molar mass (the mass of one mole of an element, measured in g/mol).

  16. What is the molar mass of... • He • Al • Ba • Rn

  17. Furthermore... • Since compounds are just atoms bonded together, you can find the molar mass of a compound by adding together the molar mass of all the elements in the compound.

  18. What is the molar mass of... • NaCl • CO2 • Be3N2 • Ca(NO3)2

  19. The Mole Road 1 mol 6.02x1023 particles 6.02x1023 particles 1 mol

  20. The Mole Road 1 mol Molar mass Molar mass 1 mol

  21. So, if you have 25 g of NaCl and want thenumber of particles… 1 mol Molar mass 6.02x1023 particles 1 mol 25 g NaCl 1 mol NaCl 6.02x1023 formula units NaCl x x 1 58.5 g NaCl 1 mol NaCl

  22. Try one on your own… • How many particles of H2O are there in 0.25 g? • How many grams of Fe2O3 are in 5.5x1024 formula units?

  23. Practice Problem #3 • How many grams of iron are in 3.5 moles?

  24. Practice Problem #4 • How many moles of Na2O are in 355.1g?

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