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 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 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 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) 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 BaCO3 + 2 NaOH

 

NaHCO3 + Ba(OH)2 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