WS 7.1 Moles!
Name:_________________________________________p.______
Part I. Intro to Avogadro’s Number
1. Fill in the blanks:
1 “pair” = _______ socks, etc.
1 “dozen” = _______ eggs, golf balls, etc.
1 “gross” = ________ things
1 “mole” = 6.02 x 1023 atoms, molecules, etc.
The number, 6.02 x 1023, is also known as “Avogadro’s Number” after the Italian scientist, Amadeo Avogadro.
It is sometimes abbreviated as NA. MEMORIZE THIS NUMBER!!!
2a. If you have 2.0 dozen water molecules, how many water molecules is this?
b. If you have 2.00 moles of water molecules, how many water molecules is this?
3a. If you have 30. eggs, how many dozen eggs is this?
b. If you have 1.505 x 1024 water molecules, how many moles of water is this?
4. How many helium atoms are in 4.6 moles of helium?
5. If you have 1.8 x 1021 carbon tetrachloride molecules, how many moles of carbon tetrachloride is this?
6a. How many oxygen (O2) molecules are in 0.0010 moles of oxygen?
b. How many atoms are in the 0.0010 mole sample of oxygen, from part (a)?
(Hint: how many atoms are in each O2 molecule?)
7a. If you have 5.00 moles of water, how many water molecules is this?
b. How many atoms are in those 5.00 moles of water?
(Hint, how many atoms are in each molecule of H2O?)
8. How many moles of carbon dioxide correspond to 6.5 x 1024 molecules?
Part II. Molar Masses.
1a. The average mass of an iron atom is 9.277 x 10-23 grams (this was discovered by experiments culminating in 1909).
What is the mass of 6.02 x 1023 iron atoms; in other words, what is the mass of 1 mole of iron atoms?
b. Iron’s atomic mass can be written as ____________________ or ____________________
2a. The average mass of a helium atom is 6.649 x 10-24 g. What is the mass of 6.02 x 1023 helium atoms; in other
words, what is the mass of 1 mole of helium atoms?
b. Helium’s atomic mass can be written as ____________________
or __________________.
3a. How many cupper atoms are in 1.00 mole of copper?___________________________
b. How many krypton atoms are in 1.00 mole of Krypton?__________________________
c. 1.00 mole of copper has a mass of 63.5 grams. 1.00 mole of Krypton has a mass of 83.8 grams.
Why does 1.00 mole of Krypton have more mass than 1.00 mole of Copper?
4. a. How many molecules are in 1.00 moles of water?______________________________
b. How many molecules are in 1.00 moles of glucose (C6H12O6) _______________________
c. Calculate the molar mass of water.
d. Calculate the molar mass of glucose.
e. Calculate the molar mass of Iron (II) nitrate: Fe(NO3)2.
f. How does 1.00 mole of water compare to 1.00 mole of glucose:
Which has more molecules? the water
the glucose
Which has more atoms?
the water
the glucose
Which has more mass?
the water
the glucose
(circle the answer for each)
they contain the same # of molecules
they contain the same # of atoms
they have the same mass
5. What if you had a mole of chemistry worksheets?
a. Given that 1 sheet of paper is 0.011 cm (or 0.00011 m) thick, how tall would a stack of 1 mole of worksheets be?
Report answer in meters.
b. Would the height of the worksheet stack (in part (a)) be greater than the following distances:
_____ Distance from the earth to the moon: 3.8 x 108 m
_____ Distance from the earth to the sun: 1.4 x 1011 m
_____ Distance to the nearest star (besides the sun); Alpha centauri system: 4 x 1016 m
_____ Diameter of our galaxy: 9 x 1020 m
_____ Distance to the edge of the observable universe: 4 x 1026 m
c. What if you stacked the worksheets end-to-end the long way? How tall/long would the stack be, in meters? Note:
the length of one sheet of paper is 11 inches, or 28 cm, or 0.28 m.