Chemistry: An Atoms-Focused Approach
Chemistry: An Atoms-Focused Approach
14th Edition
ISBN: 9780393912340
Author: Thomas R. Gilbert, Rein V. Kirss, Natalie Foster
Publisher: W. W. Norton & Company
Question
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Chapter 19, Problem 19.89QA
Interpretation Introduction

To find:

a) The fuel values of methanol and ethanol based on the thermochemical data in Appendix 4.

b) Does your answer support the prediction made in problem 19.80?

Expert Solution & Answer
Check Mark

Answer to Problem 19.89QA

Solution:

a) Fuel value of methanol is  22.67 kJ/g, and fuel value of ethanol is 29.67  kJ/g.

b) Yes; the answer supports the prediction made in problem 19.80.

Explanation of Solution

1) Concept:

To calculate the fuel value of the compound, we need to use the heat of combustion of fuel and molar mass. First we will write the combustion reaction of methanol and ethanol. Then we will calculate the Hcomb0 from the thermodynamic value, Hf0 of compounds present in the reaction. By using Hcomb0 and the molar mass of the fuel, we will calculate the fuel value. From the fuel values and the prediction made in problem 19.80, we can check if it supports

2) Formula:

i) Hcomb0 = m ×Hf, product0-n ×Hf, reactant0

ii) Fuel Value= Hcomb0molar mass ×number of moles of fuel

3) Given:

i) Methanol,   Hf0 = -238.7 kJ/mol    Chemistry: An Atoms-Focused Approach, Chapter 19, Problem 19.89QA , additional homework tip  1

ii) Methanol,   molar mass = 32.042 g/mol    Chemistry: An Atoms-Focused Approach, Chapter 19, Problem 19.89QA , additional homework tip  2

iii) Ethanol,   Hf0 = -277.7kJ/mol    Chemistry: An Atoms-Focused Approach, Chapter 19, Problem 19.89QA , additional homework tip  3

iv) Ethanol,   molar mass = 46.069 g/mol

v) O2,   Hf0 = 0.0 kJ/mol    Chemistry: An Atoms-Focused Approach, Chapter 19, Problem 19.89QA , additional homework tip  4

vi) CO2 (g),   Hf0 = -393.5 kJ/mol    Chemistry: An Atoms-Focused Approach, Chapter 19, Problem 19.89QA , additional homework tip  5

vii) H2O (l),   Hf0 = -285.8 kJ/mol    Chemistry: An Atoms-Focused Approach, Chapter 19, Problem 19.89QA , additional homework tip  6

4) Calculations:

Write the balanced combustion reaction of methanol.

2 CH3-OH l+3 O2g 2 CO2g+4 H2O l

Calculate the  Hcomb0 of methanol by using the thermodynamic value given from Appendix 4.

Hcomb0 = m ×Hf, product0-n ×Hf, reactant0

Hcomb0 = 2 × -393.5kJmol+4 × -285.8kJmol-2 × -238.7kJmol+3 × 0.0kJmol

Hcomb0 =-1930.2 kJ--477.7 kJ= -1452.8 kJ

If we divide the absolute value of Hcomb0 by twice the molar mass of methanol, we will get the fuel value.

Fuel Value= Hcomb0molar mass ×number of moles of fuel

Fuel Value= 1452.8 kJ32.042gmol ×2 mol= 22.67 kJ /g

The fuel value of methanol is 22.67 kJ/g.

Write the balanced combustion reaction of ethanol.

CH3CH2-OH l+3 O2g 2 CO2g+3 H2O l

Calculate the  Hcomb0 of ethanol by using the thermodynamic value given from Appendix 4.

Hcomb0 = m ×Hf, product0-n ×Hf, reactant0

Hcomb0 = 2 × -393.5kJmol+3 × -285.8kJmol-1 × -277.7kJmol+3 × 0.0kJmol

Hcomb0 =-1644.4 kJ--277.7 kJ= -1366.7 kJ

If we divide the absolute value of Hcomb0 by the molar mass of ethanol, we will get the fuel value.

Fuel Value= Hcomb0molar mass ×number of moles of fuel

Fuel Value= 1366.7  kJ46.069gmol ×1 mol= 29.67 kJ /g

The fuel value of ethanol is 29.67 kJ/g.

The fuel value of ethanol is higher than methanol. As the number of carbon atoms in the alcohol increases, the fuel value of alcohols increases.

Thus, the answer supports the prediction made in problem 19.80.

Conclusion:

The fuel value is calculated from the thermodynamic data, combustion reaction, and molar mass.

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Chapter 19 Solutions

Chemistry: An Atoms-Focused Approach

Ch. 19 - Prob. 19.11VPCh. 19 - Prob. 19.12VPCh. 19 - Prob. 19.13QACh. 19 - Prob. 19.14QACh. 19 - Prob. 19.15QACh. 19 - Prob. 19.16QACh. 19 - Prob. 19.17QACh. 19 - Prob. 19.18QACh. 19 - Prob. 19.19QACh. 19 - Prob. 19.20QACh. 19 - Prob. 19.21QACh. 19 - Prob. 19.22QACh. 19 - Prob. 19.23QACh. 19 - Prob. 19.24QACh. 19 - Prob. 19.25QACh. 19 - Prob. 19.26QACh. 19 - Prob. 19.27QACh. 19 - Prob. 19.28QACh. 19 - Prob. 19.29QACh. 19 - Prob. 19.30QACh. 19 - Prob. 19.31QACh. 19 - Prob. 19.32QACh. 19 - Prob. 19.33QACh. 19 - Prob. 19.34QACh. 19 - Prob. 19.35QACh. 19 - Prob. 19.36QACh. 19 - Prob. 19.37QACh. 19 - Prob. 19.38QACh. 19 - Prob. 19.39QACh. 19 - Prob. 19.40QACh. 19 - Prob. 19.41QACh. 19 - Prob. 19.42QACh. 19 - Prob. 19.43QACh. 19 - Prob. 19.44QACh. 19 - Prob. 19.45QACh. 19 - Prob. 19.46QACh. 19 - Prob. 19.47QACh. 19 - Prob. 19.48QACh. 19 - Prob. 19.49QACh. 19 - Prob. 19.50QACh. 19 - Prob. 19.51QACh. 19 - Prob. 19.52QACh. 19 - Prob. 19.53QACh. 19 - Prob. 19.54QACh. 19 - Prob. 19.55QACh. 19 - Prob. 19.56QACh. 19 - Prob. 19.57QACh. 19 - Prob. 19.58QACh. 19 - Prob. 19.59QACh. 19 - Prob. 19.60QACh. 19 - Prob. 19.61QACh. 19 - Prob. 19.62QACh. 19 - Prob. 19.63QACh. 19 - Prob. 19.64QACh. 19 - Prob. 19.65QACh. 19 - Prob. 19.66QACh. 19 - Prob. 19.67QACh. 19 - Prob. 19.68QACh. 19 - Prob. 19.69QACh. 19 - Prob. 19.70QACh. 19 - Prob. 19.71QACh. 19 - Prob. 19.72QACh. 19 - Prob. 19.73QACh. 19 - Prob. 19.74QACh. 19 - Prob. 19.75QACh. 19 - Prob. 19.76QACh. 19 - Prob. 19.77QACh. 19 - Prob. 19.78QACh. 19 - Prob. 19.79QACh. 19 - Prob. 19.80QACh. 19 - Prob. 19.81QACh. 19 - Prob. 19.82QACh. 19 - Prob. 19.83QACh. 19 - Prob. 19.84QACh. 19 - Prob. 19.85QACh. 19 - Prob. 19.86QACh. 19 - Prob. 19.87QACh. 19 - Prob. 19.88QACh. 19 - Prob. 19.89QACh. 19 - Prob. 19.90QACh. 19 - Prob. 19.91QACh. 19 - Prob. 19.92QACh. 19 - Prob. 19.93QACh. 19 - Prob. 19.94QACh. 19 - Prob. 19.95QACh. 19 - Prob. 19.96QACh. 19 - Prob. 19.97QACh. 19 - Prob. 19.98QACh. 19 - Prob. 19.99QACh. 19 - Prob. 19.100QACh. 19 - Prob. 19.101QACh. 19 - Prob. 19.102QACh. 19 - Prob. 19.103QACh. 19 - Prob. 19.104QACh. 19 - Prob. 19.105QACh. 19 - Prob. 19.106QACh. 19 - Prob. 19.107QACh. 19 - Prob. 19.108QACh. 19 - Prob. 19.109QACh. 19 - Prob. 19.110QACh. 19 - Prob. 19.111QACh. 19 - Prob. 19.112QACh. 19 - Prob. 19.113QACh. 19 - Prob. 19.114QACh. 19 - Prob. 19.115QACh. 19 - Prob. 19.116QACh. 19 - Prob. 19.117QACh. 19 - Prob. 19.118QACh. 19 - Prob. 19.119QACh. 19 - Prob. 19.120QACh. 19 - Prob. 19.121QACh. 19 - Prob. 19.122QACh. 19 - Prob. 19.123QACh. 19 - Prob. 19.124QACh. 19 - Prob. 19.125QACh. 19 - Prob. 19.126QACh. 19 - Prob. 19.127QACh. 19 - Prob. 19.128QACh. 19 - Prob. 19.129QACh. 19 - Prob. 19.130QACh. 19 - Prob. 19.131QACh. 19 - Prob. 19.132QACh. 19 - Prob. 19.133QACh. 19 - Prob. 19.134QACh. 19 - Prob. 19.135QACh. 19 - Prob. 19.136QACh. 19 - Prob. 19.137QACh. 19 - Prob. 19.138QACh. 19 - Prob. 19.139QACh. 19 - Prob. 19.140QACh. 19 - Prob. 19.141QACh. 19 - Prob. 19.142QA
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