Mole Review
1. Find the molar mass of the following compounds:
A) K3Fe(CN)6
B) C12H22O11
329.2 g/mol
342.0 g/mol
C) C2H5OH
46.0 g/mol
2. What is the mass of 1.0 mole of the following compounds?
A) Ca(NO3)2
B) CI4
C) NaHSO4
164.1 g/mol
519.6 g/mol
120.1 g/mol
A) Na2CO3
E) CH4
B) Cl2
F) OF2
C) Ag
G) O3
D) NaCl
H) KHSO4
3. Identify boxes that are elemental _______B, C, and G________
4. Identify boxes that composed of atoms ________C___________
5. Identify boxes that contain molecules __B, E, F, and G____
6. Identify boxes that contain formula units ____A, D, and H______
7. Identify boxes that contain polyatomic ions __A, and H ____
8. Identify boxes that represent molecular compounds __E and F____
9. Identify boxes that represent molecular elements ___B and G____
10. The density of oxygen gas at STP is 1.43 g/L and the density of chlorine
gas is 3.17 g/L at STP.
A. What can be inferred about the number of particles if both oxygen and
chlorine are kept in 1.0 Liter containers at STP? Explain.
Since both have the same volume at the same Temp and Pressure,
they have equal number of particles. This is according to Avogadro’s
hypothesis: EQUAL VOLUMES OF GASES AT THE SAME TEMP
AND PRESSURE HAVE EQUAL NUMBER OF PARTICLES.
B. How much more massive is a molecule of chlorine compared to a molecule of
oxygen.
3.17 g/L  1.43 g/L = 2.22. Chlorine is 2.22 time more massive than
oxygen.
C. What is the atomic mass of chlorine if oxygen’s atomic mass is 16.0 grams?
Since both chlorine and oxygen molecules are diatomic the ratio of Cl
to O atoms is also 2.22. Consequently the atomic mass of Cl is 2.22
times more massive than O or 2.22 x 16.0 = 35.5
11. Sodium chloride is determined to be composed of 39.3 % Na and 60.7%
Cl.
A. How much more or less massive is Na compared to Cl?
Since NaCl has one atom of each element then the Cl mass is 60.7 
39.3 or divided out the mass of Cl is 1.54 times more massive than
Na. Stated differently a Na atom has mass that is just a fraction that of
a Cl atom. An atom of sodium is 0.647 as massive as that of a Cl
atom.
B. What is the mass of Na relative to Cl?
(35.5)•(0.647) = mass of Na = 23.0 To the nearest tenth.
12. Suppose it is learned that Na is 1.92 times more massive than carbon.
A) What is the atomic mass of carbon to the nearest 0.l gram?
Na  C = 1.92 rewritten C = Na 1.92 = 23.0  1.92 = 12.0 mass of C
B) A compound of carbon and chlorine is formed and C makes up 7.79 % of
the total mass and 92.2% is chlorine. How much more massive is chlorine
in this compound than carbon?
Based on preceding questions Cl is 35.5 and C is 12.00 which implies
that Cl is (Cl  C) is 2.96 more massive than C.
Data from part B indicated Cl is not in a 1:1 ratio with C since ClC
=92.2 7.79 = 11.88 which is much more than the expected 2.96 if the
Cl:C ratio were 1:1. Note that 11.882.96 = 4.01. This implies there
are four times as many Cl atoms than there are C atoms.
C. What is the formula of this compound?
CCl4 This can be confirmed by determining the empirical formula from
the data in part B.
13. Hydrogen peroxide decomposes into 9.00 grams of water and 5.6 L of
oxygen at STP. How many moles of water and moles of oxygen were
formed?
1mol
mols H 2O  9.00gH 2O x
 0.500mols
18.0g
mols O2  5.6L O2 x


1mol
 0.25mols
22.4L
14. Potassium chlorate decomposes into 0.200 moles of KCl and 0.300
moles of O2. How many grams of KCl were formed and how many liters
of oxygen at STP?
74.6g
14.9grams
mol
22.4L
L of O2  0.300mol x
 6.72L
mol
gKCl  0.200mol x


15. Calcium hydroxide decomposes to produce 5.60 grams of CaO and 6.02
x 1022 molecules of H2O. How many formula units of CaO are produced
and how many grams of H2O are produced?
1mol
6.02x10 23 units
units of Ca O  5.60g x
x
 6.01x10 22 units
56.1g
1mol
gramsH2O  6.02x10 22 molecules x


16. Calcium carbonate decomposes into 8.80 grams of CO2 and 0.200 moles
of CaO. How many liters of CO2 are produced at STP, and how grams of
CaO are produced simultaneously?
L of CO2  8.80grams x
g of CaO  0.200mol x


1mol
18.0g
x
1.80grams
6.02x10 23 molecules 1mol
1mol 22.4L
x
 4.48L
44.0g 1mol
56.1g
11.2g
1mol
For questions 17-20: In the equation CaO + SO3  CaSO4, 11.24 grams of
CaO reacts with an unknown amount of SO3 to produced 27.24 grams of
CaSO4.
17. How many grams of SO3 were utilized in the reaction?
11.24 g + ? (SO3) = 27.24
X or SO3 = 16.00 grams
18. Which law concerning the composition of matter is used to answer the
previous question?
Answer: Law of Conservation of Matter.
19. How many liters of SO3 were used in the reaction?
1mole 22.4L
L of SO3  16.00g x
x
 4.47L You may also have 4.48L.
80.1g 1mole

20. How many moles of SO3 were used in the reaction?
1mole
L of SO3  16.00g x
 0.200mol
80.1g
21-23. What is the % H and % O in H2O and in H2O2?
For H2O = 2.0/18.0 x 100 = 11.1% or 11%
For H2O2 = 2.0/34.0 x 100 = 5.88 or 5.9%

22. How many grams of oxygen are present if there is 1.00 grams of O in
both H2O and H2O2?
For H2O = 16.0/18.0 x 1.00 = 0.888 grams
For H2O2 = 32.0/34.0 x 1.00 = 0.941 grams
SKIP PROBLEMS 23-25
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26. Avogadro’s hypothesis is sometimes rendered as Avogadro’s Law
expressed as
V1 V2

n1 n1
If 24.45 L of gas contains 1.00 mole of gas at 25°C and 1 atmosphere
pressure, then how many moles will be in 36.0 L at the same temperature
and pressure.
24.45L
36.0L

1.00mole x mole
27. To find the density of a gas at STP simply divide the molar mass by the
molar volume (22.4 L). What is the density of He gas?
MM
4.00g /mol
 Density 
 0.179g /mol
MV
22.4L /mol

SKIP THESE PROBLEMS 28-30
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
31. How many moles of water are needed to fill a 5.00-gallon aquarium?
One gallon is equal to 3.75L. The density of water is 1.0 g/mL.
mols of H 2O  5gal x

3.75L 1000mL 1g 1mol
x
x
x
 1000mol
1 gal
1L
1mL 18.0g