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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 . - PowerPoint PPT Presentation
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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
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 NaCl 6.02 x 1023 FUs 1 mole
2. Convert 16.3 moles CO2 to molecules
= 9.81 x 1024 molecules1mole
x 6.02 x 1023 molecules16.3 moles
3. Convert 8.9 x 1024 molecules CO2 to moles
= 15 moles CO26.02 x 1023 molecules
x 1 mole8.9 x 1024 molecules
Determining Avogadro’s Number
Produce a volume of hydrogen gas while measuring the time and electrical current.
Volume of H2 10.0 mLTime 80.7 sCurrent 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 0.07871 g/L.
It takes 1 electron to make 1 H atom
1. Calculate the number of atoms of H, starting with the time.
= 4.5976 x 1020 at1 el
x 1 at H1 couls
x 6.24 x 1018 elx 0.913 coul80.7 s
2. Calculate the number of grams H starting with the volume of H.
= 7.871 x 10-4 g H1 Lx 0.07871 g
1000 mLx 1 L 10.0 mL
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 1023 at/ 1 gram H
= 5.84 x 1023 at/ 1 mole
The Mole Song
4.5976 x 1020 at
Avogadro Facts