Stoichiometry
Problems 1
1.
When lead (II) sulfide is burned in air, lead (II) oxide and sulfur dioxide are
produced. If 0.890
moles of sulfur dioxide were
produced, how many moles of oxygen gas were required to react with
the lead (II) sulfide?
___ PbS + ___ O2 à ___ PbO
+ ___ SO2
2. In
the synthesis reaction of aluminum and oxygen to produce aluminum oxide, how
many grams of
aluminum are required to react with
0.223 moles of oxygen?
___ Al + ___ O2 à ___ Al2O3
3.
Calculate the number of grams of oxygen produced if 2.50 grams of potassium
chlorate are
decomposed completely by
heating.
___ KClO3 à ___ KCl
+ ___ O2
4.
How many moles of oxygen are needed for the complete combustion of 3.0 moles of
methane
(CH4)?
___ CH4 + ___ O2 à
___ CO2 + ___ H2O
5.
Using the same equation from #4, how many grams of carbon dioxide are formed
when 8.0 grams
of methane react? ___ CH4 + ___ O2
à ___ CO2 + ___
H2O
6.
When elemental sulfur combines with oxygen gas, sulfur dioxide is formed.
What is the total
number of grams of oxygen needed to
react completely with 2.0 moles of sulfur?
___ S + ___ O2 à ___ SO2
7. In
the synthesis of water from its elements, what is the total number of grams of
oxygen gas
needed to produce 54 grams of water? ___ H2 + ___ O2
à ___ H2O
8.
How many moles of aluminum oxide will be formed when 27 grams of aluminum react
completely
with excess oxygen
gas? ___ Al + ___ O2
à ___ Al2O3
9. What
mass (in grams) of sodium oxide is produced by the reaction of 1.44 grams of
sodium with
excess oxygen?
10. What
mass (in grams) of water will be given off when 1.92 x 1022 molecules
of octane (C8H18) are
burned
11. How many grams of Al2(SO4)3 are need to
react with KCl in order to produce 1.245 moles of
__ Al2(SO4)3 +
__ KCl à __ AlCl3 + __
K2SO4
12.
Hydrogen gas can be produced through the following unbalanced reaction.
__ Mg
+ __ HCl à
__ MgCl2 + __ H2
a. What mass of HCl is consumed
by the reaction of 2.50 moles of magnesium?
b. What mass of each product is
produced in part a.?
13.
Acetylene gas, C2H2, used in welding, produces an
extremely hot flame when it burns in pure
oxygen according to the following
unbalanced reaction.
__ C2H2 + __ O2 à
__ CO2 + __ H2O
How many molecules of CO2 are
produced when 2.50 x 104 grams of C2H2 burn
completely?
1.) 1.34 moles O2 2.)
8.02 g Al 3.)
0.980 g O2 4.) 6.0 moles O2 5.) 22 g CO2
6.) 64 g O2 7.)
48 g O2 8.)
0.50 moles Al2O3 9.) 1.94 g Na2O
10.) 5.16 g H2O 11.) 142.1
g Al2(SO4)3 12.)
a) 183 g HCl b) 238 g MgCl2; 5.00 g H2
13.) 1.16 x 1027 mcs CO2
PERCENT YIELD
1.) Use the following information to answer the
questions. In the following reaction,
41.0
grams of lead (II) chloride are
reacted with excess sodium chromate.
___
PbCl2 + ___ Na2CrO4 à ___ PbCrO4 + ___
NaCl
(A)
How many moles of lead (II) chromate will be produced?
(B)
What is the theoretical yield (in grams) of sodium chloride in this
reaction?
(C)
If a student performed this experiment and recovered 16.5 grams of
sodium
chloride, what is the
student’s percent yield?
2.) Use
the following information to answer the questions. In the following reaction, 1.70
moles of zinc nitrate are reacted
with excess chromium (II) phosphide.
___ Zn(NO3)2 + ___
Cr3P2 à ___ Zn3P2 + ___
Cr(NO3)2
(A) What is the theoretical yield (in grams) of
zinc phosphide?
(B) If a student performed this experiment and
recovered 149 grams of zinc
phosphide, what is the student’s
percent yield?
3.) Use the following information to answer the
questions. In the following reaction,
10.0
grams of copper (II) sulfate are
reacted with excess iron (III) phosphate.
___ CuSO4 + ___
FePO4 à ___ Cu3(PO4)2 + ___
Fe2(SO4)3
(A) How many grams of copper (II) phosphate can
be produced?
(B) If a student performed this experiment and
recovered 6.70 grams of copper (II)
phosphate, what is the student’s
percent yield?
Answers: 1.)
(A) 0.147 moles (B) 17.2 g (C) 95.9 %
2.) (A) 146 g (B) 102 %
3.) (A) 7.95 g (B) 84.3 %
UNIT
9 TEST REVIEW
1.)
A reaction between methane and sulfur produces carbon disulfide (CS2),
a liquid often used in the production of cellophane.
___ CH4 + ___
S8 à ___ CS2 + ___
H2S
If
1.50 moles of S8 are used, (A) how many moles of CS2 are
produced? (B) How many moles of H2S
are produced?
2.)
Lead (II) oxide is obtained by roasting galena, lead (II) sulfide, in air.
___ PbS + ___
O2 à ___ PbO
+ ___ SO2
(A)
Determine the theoretical yield (in grams) of PbO if 200.0 grams of PbS are
heated.
(B)
What is the percent yield if 170.0 grams of PbO are obtained?
3.)
Some rockets are fueled by the reaction of hydrazine (N2H2)
and hydrogen peroxide (H2O2). How many moles of nitrogen gas can be
produced by reacting 255 grams of hydrazine with excess hydrogen peroxide?
___ N2H2 + ___
H2O2 à ___ N2 + ___
H2O
4.)
One in a series of reactions that inflate automobile air bags is the
decomposition of sodium azide (NaN3).
_ NaN3 à _ Na
+ _ N2
Determine
the mass of N2 produced if 100.0 grams of NaN3 are
decomposed.
5.)
Titanium is a transition metal used in many alloys because it is extremely
strong and lightweight. Titanium
tetrachloride (TiCl4) is extracted from titanium oxide using
chlorine and carbon.
TiO2 +
C + _ Cl2
à TiCl4 + CO2
If you begin with 1.25 moles of TiO2,
what mass of Cl2 gas is needed?
6.) How many molecules of iodine can be
produced by the complete reaction of 43.97 grams of KI?
___ CuCl2 + ___
KI à ___ CuI
+ ___ KCl + ___
I2
7.) What mass of ammonia (NH3) is
needed to react completely with oxygen to produce 3.54 x 1024
molecules of water?
___ NH3 + ___
O2 à ___ NO
+ ___ H2O
ANSWERS: 1.) (A) 3.00 moles CS2 (B) 6.00 moles H2S 2.) (A) 186.6 g PbO (B) 91.10 %
3.)
8.50 moles N2 4.)
64.60 g N2 5.)
178 g Cl2 6.) 3.988 x 1022 mcs I2 7.) 66.6 g NH3
