1. A Chemist’s Dozen Today you will only need to copy slides that have a TEAL background

2. Common Measures We frequently refer to measures casually… Couple Few Dozen Baker’s Dozen Ream 2 3 12 13 500

3. Atoms are REALLY small!!! We can’t work with individual atoms or atomic mass units in the LAB – Because we can’t see things that small We work with samples large enough for us to SEE and WEIGH on a balance using units of grams.

4. This Creates a Problem… Billions of atoms are hard to keep track of in calculations A pile of atoms big enough for us to see contains billions of atoms.

5. A Chemist’s Dozen It represents a number of ‘things, just like a dozen In honor of Amedeo Avogadro, Italian chemist (1776-1856) Definition of a mole: # of atoms in exactly 12g of Carbon-12 6.022 x 10 23 is referred to as Avogadro’s Number (N A ) 1 mole (symbol: mol) = 6.02 x 10 23 atoms (or molecules)

6. The Mole (n) This is a HUGE number!!!! 1 mole = 6.02 x 10 23 particles, molecules, atoms. 1 dozen eggs =12 Eggs 1 mole of eggs = 6.02 x 10 23 Eggs

7. How Big is a Mole? A mole of marbles would cover the entire Earth’s surface 50 MILES DEEP!!!!

8. How Big is a Mole? If you spent a BILLION DOLLARS every SECOND, you couldn’t spend a mole of dollar bills in your lifetime!!!

9. How Big is a Mole? If you were able to count at the rate of 1 million numbers a second, it would take about 20 billion years to count out one mole.

10. Pop Quiz 1 dozen Mg atoms = 1 mole Mg atoms = 1 mole Mg(OH) 2 = 1 mole O 2 = 12 Mg atoms 6.02 x 10 23 Mg atoms 6.02 x 10 23 Mg(OH) 2 molecules 6.02 x 10 23 O 2 molecules

11. Moles to Particles Calculations

12. A “dozen” is an easy way to say “12”. A “mole” is an easy way to say “6.02 x 10 23”

13. There are 268 donuts. How many dozens are present? N = number = 268 donuts D = ? Dozens N D = 12 donuts per dozen D = N = 268 donuts N D 12 donuts/dozen = 22.333 dozens There are 22 dozens of donuts N D NDND

14. There are 2.46 x 10 24 donuts. How many moles are present? N = number = 2.46 x 10 24 n = moles = ? N A = Avogadro’s number = 6.02 x 10 23 n = N = 2.46x 10 24 donuts N A 6.02 x 10 23 donuts/mol = 4.0863787 mol There are 4.09 mol of donuts NANA N n

15. There are 0.50 mol of methane, CH 4 in a flask. How many molecules are present? n = 0.50 mol N A = 6.02 x 10 23 molecules/mol N = molecules =? N = n x N A = (0.50 mol)(6.02 x 10 23 molecules/mol) = 3.01 x 10 23 molecules There are 3.01 x 10 23 molecules of methane

16. In the same sample of methane, determine how many atoms of H are present In 1 molecule of CH 4, there are 4 hydrogen atoms 4 hydrogen = x x = 1.20 x 10 24 atoms of H *Note* Covalent compounds are composed of molecules. Ionic compounds are composed of formula units ______________ ____________________ 1 molecule CH 4 3.01 x 10 23 molecules

17. How many molecules are found in 1.25 mol of CO 2 ? n = 1.25 mol N A = 6.02 x 10 23 molecules/mol N = molecules =? N = n x N A = (1.25 mol)(6.02 x 10 23 molecules/mol) = 7.525 x 10 23 molecules There are 7.52 x 10 23 molecules of methane

18. How many atoms are found in 1.25 mol of CO 2 ? n = 1.25 mol N A = 6.02 x 10 23 molecules/mol N = molecules =? N = n x N A = (1.25 mol)(6.02 x 10 23 molecules/mol) = 7.525 x 10 23 molecules 7.525 x 10 23 X 3 atoms = 2.258 x 10 24 atoms 1 molecule

19. How many moles are found in 5.83 x 10 24 molecules of CO 2 ? n = ? N A = 6.02 x 10 23 molecules/mol N = 5.83 x 10 24 molecules n = N/N A = 5.83 x 10 24 molecules / 6.02 x 10 23 molecules n = 9.68 mol