1. 7.2 More Mole Conversions!!!

2. - Molecular Oxygen = O 2 - Atomic Oxygen = O from the periodic table 7 elements that exist as diatomic molecules (MEMORIZE) H 2 F 2 O 2 N 2 Cl Br 2 I 2

3. Molar Mass The mass in grams of 1 mol of a substance. Molar Mass is found using the periodic table!!! What is the molar mass of nitrogen gas? (N 2 ) 2 (14g) = 28 g

4. 1 mol of a substance = molar mass of a substance Example: What is the molar mass of nitrogen gas, N 2 ? 1 mol N 2 28 g N 2

5. Another Example What is the molar mass of molecular oxygen, O 2 ? 2 (16g) = 32 g

6. Knowing molar mass is important because it allows us to make the following conversions: mass mol representative particle

7. Ex. 1 Example problem How many grams are in 2 mol of nitrogen gas? Given: 2 mol N 2 Known: 1 mol N 2 = 28g N 2 Mol  mass 2 mol N 2 28 g N 2 = 56 g N 2 1 mol N 2

8. EX.2 How many molecules are in 84 g of nitrogen gas? Given: 84 g N 2 Known: 1 mol N 2 = 28 g N 2 1 mol N 2 = 6.02 x 10 23 molecules N 2 Mass  mol  molecules

9. How many molecules are in 84 g of nitrogen gas? Given: 84 g N 2 Known: 1 mol N 2 = 28 g N 2 1 mol N 2 = 6.02 x 10 23 molecules N 2 Mass  mol  molecules 84 g N 2 1 mol N 2 6.02 x 10 23 molecules N 2 28 g N 2 1 mol N 2 = 1.806 x 10 24 molecules

10. Your Turn Ex.3: Find the number of moles in 176 g of CO 2. Given: Known: Road Map:

11. Your Turn Ex.3: Find the number of moles in 176 g of CO 2. Given: 176 g CO 2 Known: 44 g CO 2 = 1 mol CO 2 Road Map: Mass  Mol

12. Your Turn Ex.3: Find the number of moles in 176 g of CO 2. Given: 176 g CO 2 Known: 44 g CO 2 = 1 mol CO 2 Road Map: Mass  Mol 176 g CO 2 1 mol CO 2 = 4 mol CO 2 44 g CO 2

13. Ex. 4 Find the mass of 1.2 x 10 24 molecules of NaCl Given: 1.2 x 10 24 molecules NaCl Known: Road Map:

14. Ex. 4 Find the mass of 1.2 x 10 24 molecules of NaCl Given: 1.2 x 10 24 molecules NaCl Known: 1 mol = 6.02x10 23 molecules NaCl 1 mol NaCl = 58 g NaCl Road Map: Molecules  mol  mass

15. Ex. 4 Find the mass of 1.2 x 10 24 molecules of NaCl Given: 1.2 x 10 24 molecules NaCl Known: 1 mol = 6.02x10 23 molecules NaCl 1 mol NaCl = 58 g NaCl Road Map: Molecules  mol  mass 1.2 x 10 24 molecules NaCl 1 mol NaCl 58 g NaCl 6.02x10 23 molecules 1 mol NaCl NaCl

16. Volume of a mol of a gas at STP STP: (standard temperature and pressure)  0°C or 273 K  1 atm or 101.3 kPa 1 mol of a gas occupies 22.4 L 1 mol or22.4 L 22.4L 1 mol

17. Ex. 5 Determine the volume in L of 2 mol of oxygen gas at STP. Given: 2 mol O 2 Known: 1 mol O 2 = 22.4 L Work:

18. Ex. 5 Determine the volume in L of 2 mol of oxygen gas at STP. Given: 2 mol O 2 Known: 1 mol O 2 = 22.4 L Work: 2 mol O 2 22.4 L= 44.8 L O 2 1 mol O 2

19. Your turn! Ex. 6 Determine the number of moles in 67.2 L of oxygen gas. Given: 67.2 L O 2 Known:

20. Your turn! Ex. 6 Determine the number of moles in 67.2 L of oxygen gas. Given: 67.2 L O 2 Known: 1 mol O 2 = 22.4 L Work 67.2 L O 2 1 mol O 2 = 3 mol O 2 22.4 L

21. Now we have a big road map…. Volume (L) # representative Mass moles particles

22. Ex. What is the volume of 8 g of O 2 ? Given: 8 g of O 2 Known:

23. Ex. What is the volume of 8 g of O 2 ? Given: 8 g of O 2 Known: 1 mol O 2 = 32 g O 2 1 mol O 2 = 22.4 L Road Map: Mass  Mol  volume 8 g of O 2 1 mol O 2 22.4 L = 5.6 L 32 g O 2 1 mol O 2

24. How much volume does 1.8 x 10 24 molecules of Cl 2 at STP occupy? Road Map Molecules  mol  volume

25. How much volume does 1.8 x 10 24 molecules of Cl 2 at STP occupy? Road Map Molecules  mol  volume 1.8 x 10 24 molecules of Cl 2 1 mol Cl 2 22.4 L 6.02 x 10 23 Cl 2 1 mol Cl 2 = 67.2 L

26. Density = mass/volume Units: grams / L When given density, you can calculate molar mass using the volume of 1 mol. g 22.4 L g L 1 mol mol

27. The End!!!