Name: _____________________________________________
Date: _____________________
Counting Atoms In One Gram
A mole is a quantity, just like a dozen is. A dozen is a quantity of 12 items. A mole has a
quantity of 6.02 x 10​23​ items. This enormous number is called Avogadro’s number. To help
explain Avogadro’s number and how it relates to atomic mass, complete the table below to
show various numbers of carbon atoms and hydrogen atoms, the masses of these atoms,
and the mass ratio of carbon to hydrogen. Use the first two rows as a guide.
Comparing Carbon Atoms and Hydrogen Atoms
Number of
Atoms
Carbon
Picture
Hydrogen
Mass (amu)
Picture
Mass Ratio
Mass (amu)
M ass Carbon
M ass Hydrogen
1
12
1
12 amu
1 amu
=
12
1
2
24
2
24 amu
2 amu
=
12
1
10
50
What pattern do you notice as you complete the data? ______________________________
__________________________________________________________________________
Where do we find the mass of any specific atom? ___________________________________
What would the ratio of hydrogen atoms to oxygen atoms be in a molecule of water (H​2​0)?
Explain why. ________________________________________________________________
__________________________________________________________________________
Name: _____________________________________________
Date: _____________________
When reporting molecular masses, you should give the answer with the units in amu, but if
giving the molar mass, you will need to provide an answer with units of g/mol. Ex: The
molecular mass of sodium is 23 amu, but its molar mass is 23 g/mol.
Practice identifying molar mass for elements and for compounds by completing the practice
problems below:
What is the molar mass for each element below?
1. Lithium - ________________
2. Copper - ________________
3. Gold - __________________
4. Aluminum - ______________
What is the molar mass of each compound below? Show your work, and round to the
appropriate amount of significant figures.
1. NaBr - Mass of Na: __________ Mass of Br: _________ Molar Mass: _________g/mol
2. PbSO​4​ 3. Ca(OH)​2 -​
4. Na​3​PO​4​ 5. (NH​4​)​2​CO​3​ 6. C​6​H​12​O​6​ 7. Fe​3​(PO​4​)​2​ 8. (NH​4​)​2​S 9. Zn(C​2​H​3​O​2​)​2​ 10.
AgF -
11.
AlF​3​ -