The Mega Mole Worksheet
Think of moles as a "chemist's dozen". Just as 12 eggs is a dozen
eggs, 6.02 × 1023 eggs is a mole of eggs. 6.02 × 1023 molecules of
oxygen is a mole of oxygen.
The number of grams in a mole is different from substance to
substance. If you're like most students, it's this that's confusing you.
You can find the number of grams by looking on the periodic table.
Just look at the atomic mass of the element.
Atomic Mass tells you that a carbon atom has a
mass of 12.011 atomic mass units (amu). One
mole of carbon has 12.011 grams. You will use
this number as the molar mass for carbon
Picture it this way: a dozen elephants have a different weight than a dozen rabbits- but in each case,
you have a dozen animals. Similarly, a mole of oxygen gas has a different weight than a mole of
water- but in each case, you have 6.02×1023molecules.
A mole is a standard scientific unit for measuring large quantities of very small entities such
as atoms, molecules, or other specified particles. The mole designates an extremely large number of
units, 6.02214179 × 1023, which is the number of atoms determined experimentally to be found in 12
grams of carbon-12. Carbon-12 was chosen to serve as the reference standard of the mole unit for
the International System of Units (SI).
Example 1: Convert 78g of oxygen into moles
Mass
(Grams)
Moles
1. Figure out how molar mass of oxygen (look at periodic table)
2. Use a one-step conversion to figure out the number of moles
Example 2: Convert 4.875 moles of oxygen into atom
Moles
Atoms
1. Use Avogadro’s number to convert moles to atoms
2. Use a one-step conversion to figure out the number of atoms
Example 3: Convert 78g of oxygen into atoms
Mass
(Grams)
1.
2.
3.
4.
5.
6.
Moles
Set up the given mass in the first ladder
Figure out how molar mass of oxygen (look at periodic table)
Use the molar mass of oxygen to convert to moles (grams should cancel)
Use Avogadro’s number to convert moles to atoms (moles should cancel)
Multiply across the top and bottom
Divide for final answer
Notes:
1. Convert to moles: 12.04 x 1023 atoms He
2. Convert to moles: 98.9 Na
3. Convert to grams: 10.0 moles Na
4. Convert to grams: 1x1023 atoms B
Atoms
In your group, try these problems:
For problems 5-8, convert to moles:
5. 3.01 x 1023 atoms Cu
6. 3.612 x 1023 atoms Fe
7. 24 grams S
8. 59.3 grams Sn
For problems 9-10, convert to atoms:
9. 0.000500 grams Ne
10. 220 grams Sn
On your own, find problems 11-14.
11. Convert 5.00 moles Ag to grams
12. Convert 0.0003000 moles Au to atoms
13. Convert 500g Ar to atoms
14. Convert 2.5x1024atoms Ar to grams