Mole Calculations 1

Mole Calculations 1

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.

Avogadro took 1.00 g of the smallest atom (H) and determined how many H atomsthere are in 1.00 g of H. He found that: 1.00 g H = 6.02 x 1023 atoms = 1.00 mole This is called Avogadro’s number

1 dozen donuts = 12 donuts 1 century = 100 years 1 millennium = 1000 years 1.00 mole = 6.02 x 1023 particles

The mole is a large number of particles Particle Atom element Cu 6.02 x 1023 at 1 mole Molecule covalent CH4 6.02 x 1023 molecules 1 mole Formula Unit ionic NaCl6.02 x 1023 FUs 1 mole

1. Convert 2.5 x 1025 at C to moles 2.5 x 1025 at x 1 mole = 42 moles C 6.02 x 1023 at

2. Convert 16.3 moles CO2 to molecules 16.3 moles x 6.02 x 1023 molecules = 9.81 x 1024 molecules 1mole

3. Convert 8.9 x 1024 molecules CO2 to moles x 1 mole 8.9 x 1024 molecules = 15 moles CO2 6.02 x 1023 molecules

4. Convert 28 moles NaCl to Formula Units x 6.02 x 1023 FU 28 moles = 1.7 x 1025 FUs 1mole

Determining Avogadro’s Number

Electrolysis Apparatus Ampmeter Power Supply Stop Watch

Determining Avogadro’s Number Produce a volume of hydrogen gas while measuring the time and electrical current. Volume of H210.0 mL Time 80.7 s Current0.913 amp

Background information 1 amp is defined as the number of coulombs per second. There are 6.24 x 1018 electrons in a coulomb. The density of H2 is 0.07871 g/L. It takes 1 electron to make 1 H atom

1. Calculate the number of atoms of H, starting with the time. 80.7 s x 0.913 coul x 6.24 x 1018 el x 1 at H = 4.5976 x 1020 at s 1 coul 1 el

2. Calculate the number of grams H starting with the volume of H. 10.0 mL x 1 L x 0.07871 g = 7.871 x 10-4 g H 1000 mL 1 L

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. 4.5976 x 1020 at 7.871 x 10-4 g H = 5.84 x 1023 at/ 1 gram H = 5.84 x 1023 at/ 1 mole Avogadro Facts The Mole Song

Mole Calculations 1