1. MOLES!!!

2. Atomic mass Review the mass of an atom expressed in atomic mass units is an average of the isotopes for that element listed on the periodic table

3. What is a mole? A mole is a counting number (like a dozen or a gross) the number of atoms in exactly 12 g of carbon-12

4. Molar mass the mass in grams of one mole of a substance (g/mol) same number as the atomic mass but the units are different

5. Example The average atomic mass of an Fe atom is 55.85 amu. The molar mass of Fe is 55.85 g/mol

6. Conversions To convert between moles and mass: mass = # of moles x ___g/1 mol use molar mass

7. Directions Add the examples to your 3.4 notes Copy the problems and solve the problems.

8. Example #1 Find the mass of 3.000 moles of Fe.

9. Answer #1 3.000molFe x55.85g Fe = 167.6g Fe 1 mole Fe

10. Example #2 Find the mass of 2.25 moles of Helium.

11. Answer #2 2.25 mol He x 4.00g He = 9.00 g He 1 mol He

12. Conversion #2 Converting from mass to moles. Mass (g) x 1 mole = # moles molar mass (g)

13. Example #3 How many moles of carbon in 49.5 g of carbon?

14. Answer #3 49.5 g C x 1 mol C = 4.12 mol C 12.01 g C

15. Avogadro’s number the number of atoms/particles in one mole of a substance = 6.022 x 10 23 atoms/particles 1 mole of anything is 6.022 x 10 23 of that object

16. Conversion #3 Determine the number of atoms from # moles # moles x 6.022 x 10 23 atoms = #atoms 1 mole

17. Example #4 Determine the number of atoms in 4.00 moles of carbon. The substance doesn’t matter if it is in moles.

18. Answer #4 2.41 x 10 24 C atoms 4.00 mole C x 6.022 x 10 23 C atoms 1 mole C

19. Conversion #4 To convert number of atoms to moles 9.05 x 10 25 Fe atoms x 1 mol Fe 6.022 x 10 23 Fe atoms = 150. moles of Fe

20. Example #5 Calculate the number of moles in 3.20 x 10 23 atoms of iron. The identity of the substances is not important when converting between moles & # of atoms.

21. Answer #5 0.531 moles of Fe 3.20 x 10 23 Fe atoms x 1 mole Fe 6.022 x 10 23 Fe atoms

22. Practice Add to your notes: Practice 1-4 p. 102 & practice 1-3 p. 103 Copy problem; Show work; Include units in work & answer.

23. 0.850g H x 1 mol H = 0.842 molH 1.01g H

24. Practice Problem Answers P. 102: 1. 238 g U 2. 1.2g U 3. 0.842 mol H, 0.859g H 4. 486.0 g Pb, 0.01132 mol Pb

25. p. 103 1. 4.2 x 10 23 atoms Fe 2. 0.4796 mol Ag 3. 0.58 mol Os

26. Homework p. 104: 4,5,6-10,12,13