1. Unit V: The Mole Concept Lesson 1

2. Chemical Calculations Atoms and molecules are extremely small. If they are so small and so light, how can we weigh them? We weigh large numbers of them.

3. Avogadro took 1.00 g of the smallest atom (H) and determined how many H atoms there are in 1.00 g of H. He found that: 1.00 g H = 6.02 x 10 23 atoms = 1.00 mole This is called Avogadro’s number

4. Your new best friend… Avogadro’s number = 6.02 x 10 23

6. 1 dozen donuts = 12 donuts 1 century = 100 years 1 millennium = 1000 years 1.00 mole = 6.02 x 10 23 particles

7. The mole is a large number of particles Particle AtomelementsCu 6.02 x 10 23 atoms 1 mole MoleculecompoundsCH 4 6.02 x 10 23 molecules 1 mole

8. The Mole & Avogadro’s number

10. 1. Convert 2.5 x 10 25 atoms of Carbon to moles = 42 moles C 6.02 x 10 23 atoms x 1 mole2.5 x 10 25 atoms

11. 2. Convert 16.3 moles CO 2 to molecules = 9.81 x 10 24 molecules 1mole x 6.02 x 10 23 molecules16.3 moles

12. 3. Convert 8.9 x 10 24 molecules CO 2 to moles

13. 4. Convert 28 moles NaCl to molecules

14. Avogadro’s Hypothesis

15. Avogadro’s Hypothesis: Equal volumes of different gases, at the same temperature and pressure, contain the same number of particles.

16. V.1 AVOGADRO’S HYPOTHESIS Avogadro’s hypothesis: Equal volumes of different gases contain the same number of particles (at the same temperature and pressure). If 1L of gas A reacts with 1L of gas B, then the formula for the compound is AB If 2 L of gas A reacts with 1L of gas B, then the formula for the compound is A 2 B If 2 L of gas A reacts with 3L of gas B, then the formula for the compound is __________________

17. Avogadro’s hypothesis In other words, however many litres of a certain gas you have, it will be represented as a subscript for that particular gas. Only under constant temperature & pressure.

18. Try… If 2 L of an unknown gas X contains 4 x 10 23 molecules at a certain temperature and pressure. How many molecules are present in 4 L of oxygen gas at the same temperature and pressure?

19. Homework Questions: p. 78 #2-5