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 10 23 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 10 23 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 10 25 atoms He?How many moles are in 2.57 x 10 25 atoms He?

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

10. Two Step Problems (the mole road) We have now discussed moles in two ways—as particles (1 mol = 6.02x10 23 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 CO 2 Be 3 N 2 Ca(NO 3 ) 2

19. 1 mol 6.02x10 23 particles 1 mol

20. Molar mass 1 mol

21. So, if you have 25 g of NaCl and want the number of particles… 1 mol Molar mass 6.02x10 23 particles 1 mol 25 g NaCl 1 1 mol NaCl 58.5 g NaCl 6.02x10 23 formula units NaCl 1 mol NaCl xx

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 Na 2 O are in 355.1g?