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

5. The mole is a large number of particles Particle AtomelementCu 6.02 x 10 23 at 1 mole MoleculecovalentCH 4 6.02 x 10 23 molecules 1 mole Formula UnitionicNaCl 6.02 x 10 23 FUs 1 mole

6. 1. Convert 2.5 x 10 25 at C to moles = 42 moles C 6.02 x 10 23 at x 1 mole2.5 x 10 25 at

7. 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

8. 3. Convert 8.9 x 10 24 molecules CO 2 to moles = 15 moles CO 2 6.02 x 10 23 molecules x 1 mole 8.9 x 10 24 molecules

9. = 1.7 x 10 25 FUs 1mole x 6.02 x 10 23 FU 28 moles 4. Convert 28 moles NaCl to Formula Units

10. Determining Avogadro’s Number

11. Ampmeter Power Supply Stop Watch Electrolysis Apparatus

12. Determining Avogadro’s Number Produce a volume of hydrogen gas while measuring the time and electrical current. Volume of H 2 10.0 mL Time80.7 s Current0.913 amp

13. Background information 1 amp is defined as the number of coulombs per second. There are 6.24 x 10 18 electrons in a coulomb. The density of H 2 is 0.07871 g/L. It takes 1 electron to make 1 H atom

14. 1. Calculate the number of atoms of H, starting with the time. = 4.5976 x 10 20 at 1 el x 1 at H 1 couls x 6.24 x 10 18 elx 0.913 coul80.7 s

15. 2. Calculate the number of grams H starting with the volume of H. = 7.871 x 10 -4 g H 1 L x 0.07871 g 1000 mL x 1 L10.0 mL

16. 3. Divide the atoms of H by the grams of H to get the number of H atoms in a gram which is Avogadro’s number. 7.871 x 10 -4 g H =5.84 x 10 23 at/ 1 gram H =5.84 x 10 23 at/ 1 mole The Mole Song 4.5976 x 10 20 at Avogadro Facts