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# Molar Mass - PowerPoint by rt3463df

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```									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 atoms there are in 1.00 g of H.
He found that:

1.00 g H = 6.02 x 1023 atoms = 1.00 mole

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          NaCl   6.02 x 1023 FUs
1 mole
1. Convert 2.5 x 1025 at C to moles

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

8.9 x 1024 molecules   x   1 mole                =   15 moles CO2
6.02 x 1023 molecules
4. Convert 28 moles NaCl to Formula Units

28 moles   x   6.02 x 1023 FU     = 1.7 x 1025 FUs
1mole
Ampmeter                    Electrolysis Apparatus

Power Supply

Stop Watch

Produce a volume of hydrogen gas while measuring the time and
electrical current.

Volume of H2                       10.0 mL
Time                               80.7 s
Current                            0.913 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 0.08428 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      1L      x     0.08428 g
1000 mL            1L         = 8.428 x 10-4 g H
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
8.428 x 10-4 g H

=       5.45 x 1023 at/ 1 gram H

=       5.45 x 1023 at/ 1 mole