Chapter 12 Practice Test
Stoichiometry
Directions: Answer the following questions in the spaces provided. Show as much work as possible. Maintain 3 decimal places
throughout your calculations. Box your answers & include units!
Balance the following:
1.
_____Al + _____Fe2O3  _____Fe + _____Al2O3
2.
_____PbCl2 + _____Li2SO4  _____PbSO4 + _____LiCl
3.
_____Cl2 + _____KBr  _____KCl + _____Br2
Sample: Convert 60g NaOH to formula units NaOH
60g NaOH
1 mol NaOH
39.997g NaOH
6.02 x 1023 units NaOH
1 mol NaOH
9.031 x 1023 units NaOH
4. Convert 44.1g NaHCO3 to formula units NaHCO3
=
Sample: Given the unbalanced reaction, TiCl4 +
a.
Write the balanced equation:
H2O 
TiCl4 +
TiO2 + HCl
2H2O 
TiO2 + 4HCl
How many moles of HCl would be produced from:
b.
2 moles of TiCl4
8 moles HCl
c.
0.5 moles of H2O
1 mole HCl
b. since the mole ratio of TiCl4 : HCl is 1:4, the number of moles of HCl must always be 4 times the moles of TiCl 4
c. since the mole ratio of H2O : HCl is 2:4, the number of moles of HCl must always be 2 times the moles of H2O
5. Given the unbalanced reaction, Fe + H2O  Fe3O4 + H2
a.
Write the balanced equation:
How many moles of Fe3O4 would be produced from:
b.
2.5 moles of Fe
c.
1.5 moles of H2O
Sample: Given the equation Zn + CrCl3  CrCl2 + ZnCl2, find the mass of ZnCl2 formed if 1.2 x 1024 formula units of CrCl3
reacts with an excess of Zn.
1Zn +
2CrCl3
→ 2CrCl2 + 1ZnCl2
Analyze, rewrite, balance equation
24
1.2 x 10 part.
.
?g
Solve for only
reactant
1.2 x 1024 part.
CrCl3
1 mol CrCl3
x
6.02 x1023 part.
CrCl3
x
1 mol
ZnCl2
2 mol
CrCl3
x
136.286g
ZnCl2
1 mol ZnCl2
= 135.83g
ZnCl2
6. Given the equation WO3 + H2  W + H2O, find the mass of W formed if 3.0 x 10 22 formula units of WO3 reacts with an excess
of H2.
Chapter 12 Practice Test
Stoichiometry
Sample: Given the equation RbCl + O2  RbClO4, find the mass of RbClO4 formed if 2.7g of O2 reacts with 135g RbCl.
1RbCl + 2O2 → 1RbClO4
Analyze, rewrite, balance equation
135g
2.7g
?g
Solve for 1st reactant
135g RbCl
Solve for 2nd reactant
2.7g O2
1 mol RbCl
120.921g RbCl
x
x
1 mol O2
31.998g O2
x
x
1 mol RbClO4
1 mol RbCl
1 mol RbClO4
2 mol O2
184.917g RbClO4
1 mol RbClO4
x
x
184.917g RbClO4
1 mol RbClO4
= 206.45g RbClO4
= 7.80g RbClO4
In a limiting reactant problem the correct answer will be the lower of the two calculated values.
7. Given the unbalanced equation CH4 + O2  CO2 + H2O, find the mass of CO2 produced from the reaction of 56.1g of CH4
with 91.2g of O2.
Sample: Using the equation Al + CuSO4 → Cu + Al2(SO4)3, calculate the percent yield if you experimentally
produce 3.65 grams of copper when 1.87 grams of aluminum reacts with 9.65 grams of copper (II) sulfate.
2Al + 3CuSO4 → 3Cu + Al2(SO4)3
Analyze, rewrite, balance equation
1.87g
Solve for 1st reactant
Solve for 2nd reactant
1.87g Al
9.65g CuSO4
Calculate % yield =
x
x
1 mol Al
26.982g Al
9.65g
x
1 mol CuSO4
159.608g CuSO4
?g
3 mol Cu
2 mol Al
x
actual yield (from question)
x 100
theoretical yield (calculated above)
x
63.546g Cu
1 mol Cu
3 mol Cu
3 mol CuSO4
→ →
x
= 6.61g Cu
63.546g Cu
1 mol Cu
= 3.84g Cu
3.65g Cu
x 100 = 95.1%
3.84g Cu
8. Given the unbalanced equation Ba(NO3)2 + Na2CrO4  BaCrO4 + NaNO3, find the mass of NaNO3 formed if
18.6g Ba(NO3)2 reacts with 46.1g Na2CrO4.
When the reaction is carried out, 10.5 g of NaNO3 is formed. Calculate the percent yield.
Form A