Chemistry: An Atoms-Focused Approach (Second Edition)
Chemistry: An Atoms-Focused Approach (Second Edition)
2nd Edition
ISBN: 9780393614053
Author: Thomas R. Gilbert, Rein V. Kirss, Stacey Lowery Bretz, Natalie Foster
Publisher: W. W. Norton & Company
Question
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Chapter 9, Problem 9.95QA
Interpretation Introduction

To estimate:

The difference in Hrxno values between the incomplete combustion of one mole of ethane to carbon monoxide and water vapor and the complete combustion of ethane to carbon dioxide and water vapor using average bond energies.

Expert Solution & Answer
Check Mark

Answer to Problem 9.95QA

Solution:

The difference in Hrxno values between the incomplete and complete combustion of one mole of ethane is 554 kJ.

Explanation of Solution

1) Concept:

Bond energy is the amount of energy required when one mole of bonds in the gas phase is broken.

This can be used to calculate the heat of reaction (enthalpy change) by combining the H values (bond energies) for bonds that are broken and bonds that are formed.

H values are positive for bonds broken.

H values are negative for bonds formed.

Hrxno=Hf bond breakingo-Hf  bond formingo

The balanced equation for the incomplete combustion of ethane to carbon monoxide and water vapor is

2C2H6(g)+5O2(g)4CO(g)+6H2O(g)

The balanced equation for the complete combustion of ethane to carbon dioxide and water vapor is

2C2H6(g)+7O2(g)4CO2(g)+6H2O(g)

2) Formula:

Hrxno=Hf bond breakingo-Hf  bond formingo

3) Given:

Bond energies from Appendix 4: Table A4.1

Bonds Bond energy (kJ/mol)
C=O 799
C-H 413
O-H 463
CO 1072
C-C 348
O=O 498

4) Calculations:

a) Hrxno for incomplete combustion:

2C2H6(g)+5O2(g)4CO(g)+6H2O(g)

Bonds Number of bonds (mol) Bond energy (kJ/mol) ΔH
Bonds broken O=O 5 498 kJ/mol 5 mol ×498 kJ/mol
C-H 12 413 kJ/mol 12 mol ×413 kJ/mol
C-C 2 348 kJ/mol 2 mol ×348 kJ/mol
Bonds formed O-H 12 463 kJ/mol -12 mol ×463 kJ/mol
CO 4 1072 kJ/mol -4 mol ×1072 kJ/mol

Hrxno=5 mol ×498 kJ/mol+12 mol ×413 kJ/mol+2 mol ×348 kJ/mol-12 mol ×463 kJ/mol+4 mol ×1072 kJ/mol

Hrxno=8142 kJ-9844 kJ

Hrxno=-1702 kJ

Hrxno for 1 mol of ethane is -851 kJ.

b) Hrxno for complete combustion:

2C2H6(g)+7O2(g)4CO2(g)+6H2O(g)

Bonds Number of bonds (mol) Bond energy (kJ/mol) ΔH
Bonds broken O=O 7 498 kJ/mol 7 mol ×498 kJ/mol
C-H 12 413 kJ/mol 12 mol ×413 kJ/mol
C-C 2 348 kJ/mol 2 mol ×348 kJ/mol
Bonds formed O-H 12 463 kJ/mol -12 mol ×463 kJ/mol
C=O 8 799 kJ/mol -8 mol ×799 kJ/mol

Hrxno=7 mol ×498 kJ/mol+12 mol ×413 kJ/mol+2 mol ×348 kJ/mol-12 mol ×463 kJ/mol+8 mol ×799 kJ/mol

Hrxno=9138 kJ-11948 kJ

Hrxno=-2810 kJ

Hrxno for 1 mol of ethane is -1405 kJ.

The difference between Hrxno of incomplete and complete combustion of 1 mole of ethane is

Hrxno=1405 kJ-851 kJ=554 kJ

Conclusion:

We calculated Hrxno for 1 mole of ethane for both incomplete and complete combustion and then took their difference.

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Chapter 9 Solutions

Chemistry: An Atoms-Focused Approach (Second Edition)

Ch. 9 - Prob. 9.11QACh. 9 - Prob. 9.12QACh. 9 - Prob. 9.13QACh. 9 - Prob. 9.14QACh. 9 - Prob. 9.15QACh. 9 - Prob. 9.16QACh. 9 - Prob. 9.17QACh. 9 - Prob. 9.18QACh. 9 - Prob. 9.19QACh. 9 - Prob. 9.20QACh. 9 - Prob. 9.21QACh. 9 - Prob. 9.22QACh. 9 - Prob. 9.23QACh. 9 - Prob. 9.24QACh. 9 - Prob. 9.25QACh. 9 - Prob. 9.26QACh. 9 - Prob. 9.27QACh. 9 - Prob. 9.28QACh. 9 - Prob. 9.29QACh. 9 - Prob. 9.30QACh. 9 - Prob. 9.31QACh. 9 - Prob. 9.32QACh. 9 - Prob. 9.33QACh. 9 - Prob. 9.34QACh. 9 - Prob. 9.35QACh. 9 - Prob. 9.36QACh. 9 - Prob. 9.37QACh. 9 - Prob. 9.38QACh. 9 - Prob. 9.39QACh. 9 - Prob. 9.40QACh. 9 - Prob. 9.41QACh. 9 - Prob. 9.42QACh. 9 - Prob. 9.43QACh. 9 - Prob. 9.44QACh. 9 - Prob. 9.45QACh. 9 - Prob. 9.46QACh. 9 - Prob. 9.47QACh. 9 - Prob. 9.48QACh. 9 - Prob. 9.49QACh. 9 - Prob. 9.50QACh. 9 - Prob. 9.51QACh. 9 - Prob. 9.52QACh. 9 - Prob. 9.53QACh. 9 - Prob. 9.54QACh. 9 - Prob. 9.55QACh. 9 - Prob. 9.56QACh. 9 - Prob. 9.57QACh. 9 - Prob. 9.58QACh. 9 - Prob. 9.59QACh. 9 - Prob. 9.60QACh. 9 - Prob. 9.61QACh. 9 - Prob. 9.62QACh. 9 - Prob. 9.63QACh. 9 - Prob. 9.64QACh. 9 - Prob. 9.65QACh. 9 - Prob. 9.66QACh. 9 - Prob. 9.67QACh. 9 - Prob. 9.68QACh. 9 - Prob. 9.69QACh. 9 - Prob. 9.70QACh. 9 - Prob. 9.71QACh. 9 - Prob. 9.72QACh. 9 - Prob. 9.73QACh. 9 - Prob. 9.74QACh. 9 - Prob. 9.75QACh. 9 - Prob. 9.76QACh. 9 - Prob. 9.77QACh. 9 - Prob. 9.78QACh. 9 - Prob. 9.79QACh. 9 - Prob. 9.80QACh. 9 - Prob. 9.81QACh. 9 - Prob. 9.82QACh. 9 - Prob. 9.83QACh. 9 - Prob. 9.84QACh. 9 - Prob. 9.85QACh. 9 - Prob. 9.86QACh. 9 - Prob. 9.87QACh. 9 - Prob. 9.88QACh. 9 - Prob. 9.89QACh. 9 - Prob. 9.90QACh. 9 - Prob. 9.91QACh. 9 - Prob. 9.92QACh. 9 - Prob. 9.93QACh. 9 - Prob. 9.94QACh. 9 - Prob. 9.95QACh. 9 - Prob. 9.96QACh. 9 - Prob. 9.97QACh. 9 - Prob. 9.98QACh. 9 - Prob. 9.99QACh. 9 - Prob. 9.100QACh. 9 - Prob. 9.101QACh. 9 - Prob. 9.102QACh. 9 - Prob. 9.103QACh. 9 - Prob. 9.104QACh. 9 - Prob. 9.105QACh. 9 - Prob. 9.106QACh. 9 - Prob. 9.107QACh. 9 - Prob. 9.108QACh. 9 - Prob. 9.109QACh. 9 - Prob. 9.110QACh. 9 - Prob. 9.111QACh. 9 - Prob. 9.112QACh. 9 - Prob. 9.113QACh. 9 - Prob. 9.114QACh. 9 - Prob. 9.115QACh. 9 - Prob. 9.116QACh. 9 - Prob. 9.117QACh. 9 - Prob. 9.118QACh. 9 - Prob. 9.119QACh. 9 - Prob. 9.120QACh. 9 - Prob. 9.121QACh. 9 - Prob. 9.122QACh. 9 - Prob. 9.123QACh. 9 - Prob. 9.124QACh. 9 - Prob. 9.125QACh. 9 - Prob. 9.126QACh. 9 - Prob. 9.127QACh. 9 - Prob. 9.128QACh. 9 - Prob. 9.129QACh. 9 - Prob. 9.130QA
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