3. Monday, March 17 th : “A” Day Tuesday, March 18 th : “B” Day Agenda  Ch. 6 Tests  Begin Chapter 7: “The Mole and Chemical Composition”  In-Class Assignments: Practice pg. 228: #1-4 Practice pg. 229: #1-4 Concept Review: “Avo’s Number/Molar Conversions”  Homework: pg. 21/22 worksheet MUST SHOW WORK!

4. Ch. 6 Tests “Covalent Compounds” ClassAverage Grade (out of 65) Average Percentage 2A 54.35 83.63% 4A 55.80 85.85% 1B 58.11 89.40% 3B 60.45 93.00%

5. Start Section 7.1: “Avogadro’s Number and Molar Conversions”  Atoms, ions, and molecules are very small, so even tiny samples have huge numbers of particles.  Scientists use the mole to make counting such large numbers easier.  Mole: the SI unit for amount; the number of atoms in exactly 12 grams of carbon-12.

6. The Mole is a Counting Unit  The mole is used to count out a given number of particles, whether they are atoms, molecules, formula units, ions, or electrons.  The mole is just one kind of counting unit: 1 dozen = 12 objects 1 roll = 50 pennies 1 hour = 3,600 seconds 1 pair = 2 items 1 mole = 6.022  10 23 particles

7. Avogadro’s Number & the Mole  The number of particles in a mole is called Avogadro’s Number.  Avogadro’s number is 6.022  10 23 ; the number of atoms or molecules in 1.000 mole Lorenzo Romano Amedeo Carlo Avogadro Born in Turin, Italy, on August 9th, 1776.

8. Conversion Factors are Equivalent to 1  The definition of one mole is: 6.022  10 23 particles = 1 mol  From this definition, we get 2 conversion factors: 6.022 X 10 23 particles = 1 1 mol _____1 mol________ = 1 6.022 X 10 23 particles

9. Use the Conversion Factor that Cancels Out the Known Units  Because a conversion factor is equal to 1, it can multiply any quantity without changing the value.  Only the units are changed.  When solving problems, the unit that you know goes on the bottom of the fraction.

10. You Can use Conversion Factors to Change from One Unit to Another (Dimensional Analysis ) Example #1: How many eggs are there in 5 dozen? 1.Start with what you know: 5 dozen 2.Multiply by a conversion factor to change dozen number of eggs:  5 dozen X 12 eggs = 60 eggs 1 dozen

11. Example #2: If you have 548 plain white socks, how many pairs can you make? 1. Start with what you know: 548 socks 2.Multiply by a conversion factor to change socks pairs of socks:  548 socks X 1 pair = 2 socks 274 pairs You Can use Conversion Factors to Change from One Unit to Another (Dimensional Analysis )

12. Changing Moles Particles Sample Problem A, pg 228 Find the number of molecules in 2.5 mol of sulfur dioxide, SO 2. 1.Start with what you know: 2.5 mol SO 2 2.Multiply by a conversion factor to change moles molecules:  2.5 mol SO 2 X 6.022 X 10 23 molecules SO 2 = 1 mole SO 2 1.5 X10 24 (2 sig figs) molecules SO 2

13. Changing Moles Particles Practice #1 How many particles are there in 2.45 X 10 -6 mol of nickel, Ni(II) selenide, NiSe? 1.Start with what you know: 2.45 X 10 -6 mol NiSe 2.Multiply by conversion factor to change moles particles:  2.45 X 10 -6 mol NiSe X 6.022 X 10 23 particles NiSe = 1 mole NiSe 1.48 X 10 18 particles (3 sig figs) NiSe

14. Changing Moles Particles Practice #2 How many atoms are there in 4.3 moles of tungsten, W? 1.Start with what you know: 4.3 moles W 2.Multiply by conversion factor to change moles atoms:  4.3 mol W X 6.022 X 10 23 atoms W = 1 mol W 2.6 X 10 24 atoms W (2 sig figs)

15. So far, we’ve been changing moles particles Do you think we can go the other way, and change particles moles? Of course we can, and that’s what we’re going to do!

16. Changing Particles Moles Sample Problem B, pg. 229 A sample contains 3.01 X 10 23 molecules of sulfur dioxide, SO 2. Determine the amount in moles. 1. Start with what you know: 3.01 X 10 23 molecules SO 2 2.Multiply by conversion factor to change molecules moles:  3.01 X 10 23 molecules SO 2 X __1 mole SO 2 ______ 6.022 X 10 23 molecules SO 2 0.500 mole SO 2 (3 sig figs)

17. Changing Particles Moles Practice #1 How many moles are equivalent to 6.93 X 10 23 thallium atoms, Tl? 1. Start with what you know: 6.93 X 10 23 Tl atoms 2.Multiply by conversion factor to change atoms moles:  6.93 X 10 23 Tl atoms X 1 mole Tl = 6.022 X 10 23 Tl atoms (3 sig figs) 1.15 mole Tl

18. Changing Particles Moles Practice #2 How many moles are equivalent to 7.95 X 10 24 copper (II) chloride, CuCl 2, formula units? 1. Start with what you know: 7.95 X 10 24 CuCl 2 formula units 2.Multiply by conversion factor to change formula units moles:  7.95 X 10 24 form. unit CuCl 2 X ____1 mole_CuCl 2 ___ 6.022 X 10 23 form. unit CuCl 2 13.2 mol CuCl 2 (3 sig figs)

19. In-Class Assignments/Homework  Practice pg. 228: #1-4  Practice pg. 229: #1-4 Homework:  Practice Worksheets, pg. 21/22  Concept Review: Avogadro’s Number and Molar Conversions” #1-5 You must SHOW WORK to get credit!