3. Tuesday, April 2 nd : “A” Day Wednesday, April 3 rd : “B” Day Agenda  ACT practice  Begin Chapter 7: “The Mole and Chemical Composition”  In-Class Assignments: Practice pg. 228: #1-4 Practice pg. 229: #1-4  Homework: Practice worksheet, pg. 21/22: MUST SHOW WORK! Concept Review: “Avo’s Number/Molar Conversions”

4. ACT Practice Worksheets  Take some time to complete ACT practice worksheets.  When you’re done, turn them in and pick up the notes for today.  Yes, these will be graded…

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

13. 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

14. 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

15. 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)

16. We can go the other way too and change particles moles

17. 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)

18. 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

19. 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)

20. 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!