CHM
2045C Name: _________________
Module Five III Homework Packet
Module Five Part III: Chemical
Equations & Stoichiometry (Chapter 3)(Jespersen)
I.______(02) Mole-Mole Problems
Sections 3.3 Answers
ij (Top)
J._____ (02) Mass-Mass Stoichiometric Problems-Sections 3.3 Answers ij (bottom)
K._____(02) Excess/Limiting Reagent
Problems-Section 3.5 Answers kl
(Top)
L._____
(02) Per
Cent Yield Problems/Impure Reagents-Section 3.4 Answers kl
(bottom)
N._____(05) Multi step Synthesis
Problems-Lecture Answers
O._____(05) Mixture Problem
Lecture Answers 2nd
Example Combined Example
P. ____(05) Empirical Formula
from Analysis – Answers Section 3.11
______(23) Total
Module
Five III Chapter 3
Part I Mole-Mole Stoichiometry 2 points
Part I Mole-Mole Stoichiometry 2 points
Homework #1:
Tungsten occurs in the important mineral sheelite (Calcium tungstate), which is
converted to tungstic acid. Tungsten is
then extracted from tungstic acid by the following (unbalanced) reaction:
H2 +
H2WO4 à W
+ H2O
How moles of hydrogen is needed to prepare 6 moles of elemental
tungsten?
Homework #2:
Phosphoric acid can be made by the following (unbalanced) reacti
H2O + P4O10 à
H3PO4
How many moles of
Phosphoric acid can be prepared from the combination of 5 moles of
Tetraphosphorus decoxide with excess water?
2045 McMurry 2045: no references ;
Jespersen Section 3.3 see worked example 3.14 page 132
p151 Question #3.113 & 3.114
1025 Corwin 1025: see worked Examples 9.4 page 256 and 9.5 page 257
additional Suggested Problems: Page 274 #19-28
Part J Mass-Mass Stoichiometry 02 points
Use this concept map for Part J Mass-Mass Problems:
The Solution to: __?____gHg = 1.25g 1.25 gHgO
Part J Mass-Mass Stoichiometry 02 points
Homework #3: Toluene and nitric acid are used in the
production of trinitrotoluene (TNT), an explosive:
C7H8 +
HNO3 à C7H5N3O6 +
H2O (Unbalanced)
Calculate the mass
of TNT that can be made from 192 g of C7H8 (toluene).
Homework #4: What mass of carbon dioxide is produced from the combustion of 176 grams
of propane gas ,
C3H8 , in excess oxygen gas, O2. Water is the only other product.
Reference:
Jespersen Section 3.3
see worked Example 3.15 pages 134-135
additional Suggested Problems: Page 151 Questions 3.115 - 3.122
Part K Excess-Limiting Reagent
Problem 02 points
Sample Limiting Reagent Problem
(M-5K)
Part K Excess-Limiting Reagent
Problem 2 points
Homework #5: How
many grams of Calcium phosphate can be made according to the reaction
(unbalanced):
CaCl2 + K3PO4 ----> Ca3(PO4)2 +
KCl
by mixing a
solution of 5.00 grams of CaCl2 with another
containing 8.00 grams of Potassium phosphate?
Reference:
Jespersen Section 3.5
see worked Examples 3.17 pages 138-139
additional Suggested Problems: p152 Problems 3.122-3.130
Part L Impure
Reagents/Percent
Yield Problem 2 points
Reference:
Jespersen Section 3.7
see worked Examples 3.18 pages 141-143
Practice Exercises 3.32 and 3.23 page 140
additional Suggested Problems: p152-3 Problems 3.131-3.136
Part L Impure
Reagents/Percent
Yield Problem 2 points
Homework #6: A laboratory manual calls for 13.0
grams of butanol reactant in excess sodium bromide and sulfuric acid as
reactants in this reaction:
C4H9OH +
NaBr + H2SO4 ------> C4H9Br + NaHSO4 + H2O
A
student following these directions obtains 16.8 grams of butyl bromide (C4H9Br). What is the theoretical yield and the
percent yield of this reaction?
Module Five Part N Multi Step Synthesis Problem 05 points
Reference:
Jespersen Section 3.7 page 143 Very
Little Exlanation
no worked Examples
no Practice Exercises
no additional Suggested Problems
Module Five Part N Multi Step Synthesis Problem 5 points
Homework #7:
Potassium perchlorate may be made by the following series of
reactions:
Cl2 + 2
KOH ----> KCl
+ KClO +
H2O
3 KClO -----> 2 KCl
+ KClO3
4 KClO3
-----> 3 KClO4 +
KCl
How much Cl2 is needed to prepare 100 g of Potassium perchlorate KClO4 by
the above sequence?
A harder question would be to ask how many
grams of KCl byproduct is formed in the three
reactions?
Module Five Part N Multi Step Synthesis Problems
continued
Homework #7.1:
How many kilograms of pure Sulfuric acid could be
obtained for 0ne kilogram of pure Iron Pyrites (FeS2) according to the
following reactions:
4 FeS2 + 11 O2 ----> 2 Fe2O3 +
3 SO2
2 SO2
+ O2 ----> 2 SO3
SO3
+ H2O ----> H2SO4
Answer: 1.63 kg H2SO4
How many kilograms of pure oxygen gas would be
required?
Module Five Part N Multi Step Synthesis Problems
continued
Homework #7.2:
Hydrozoic acid , HN3
, may be made from the following sequence
of reactions:
N2 + 3 H2 ---->
2 NH3
4 NH3 +
Cl2 ---> N2H4 +
2 NH4Cl
4 NH3 +
5 O2 ----> 4
NO +
6 H2O
2 NO +
O2 ----> 2 NO2
2 NO2 + 2 KOH ----> KNO2 + KNO3 + H2O
2 KNO2 +
H2SO4
----> K2SO4 +
2 HNO2
N 2H4 + HNO2 ---->
HN3 + 2 H2O
If there is no recovery of NH4Cl and KNO3,
how much hydrogen and how much chlorine will be needed to make 100 g of HN3?
Answer: 42g of H2 and 164 g CL2
Module Four Part O Mixture Problems 07 points (03.5
each)
Homework #8:
Sodium
hydrogen carbonate, NaHCO3 can be decomposed quantitatively by heating:
2 NaHCO3 (s) à Na2CO3 (s) + CO2 (g)
+ H2O (g)
A 0.682 g sample of impure NaHCO3
yielded a solid residue (consisting of Na2CO3 and other
solids) with a mass of 0.467 g. What was
the mass percent of NaHCO3 in the sample?
Module Four Part O Mixture Problems Continued
Homework #9:
A mixture of NaHCO3 and Na2CO3 weighed
1.0235 g. The dissolved mixture was reacted with excess Ba(OH)2
to form 2.1028 g of BaCO3 by the following reaction:
Na2CO3 +
Ba(OH)2 à BaCO3 +
2 NaOH
NaHCO3 +
Ba(OH)2 à BaCO3 +
NaOH + H2O
What
was the percentage of NaHCO3 in the original mixture?
ANSWER: 39.5% NaHCO3
see worked Examples
additional Suggested Problems:
Module Four Part P Determining the Formula of
a Compound by Combustion
10 points
Module Four Part P Determining the Formula of
a Compound by Combustion
05
points
Homework #10:
A 0.523 g sample of the unknown compound CxHy, is burned in air to give 1.612 g
of CO2 and 0.7425g of H2O. A separate experiment gave a
molar mass for CxHy of 114 g/mol. Determine the empirical and
molecular formula for the hydrocarbon.
Additional
Combustion Problems:
Read
Section 3.12 pages 93-96 McMurry 5th
See
worked example 3.18 page 95 and try problems 3.27 page
95.
End
of chapter 3.98, 3.99 page 104.
Q#
36-43 p 142 Kotz 5th Edition
Module
5 Combined Mixture/Multistep Problem (Bonus)
Homework #11:
A mixture of Sodium chloride and sodium
bromide, weighing 3.5084 grams was dissolved and treated with enough Silver
nitrate to precipitate all the chloride and bromide as silver chloride and
silver bromide. The washed precipitate
was treated with KCN to solubilize the silver and resulting solution was
electrolyzed. The equations are:
NaCl + AgNO3 ---->
AgCl + NaNO3
NaBr +
AgNO3 ----> AgBr
+ NaNO3
AgCl +
2 KCN -----> KAg(CN)2
+ KCl
AgBr +
2 KCN -----> KAg(CN)2
+ KBr
4 KAg(CN)2
+ 4 KOH
------> 4 Ag +
8 KCN + O2 + 2
H2O
After the following
step was complete the deposit of metallic silver weighed 5.502 grams. What was the composition of the initial
mixture?
ANSWER: 65.23% NaCl 34.77 % NaBr