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 12, Problem 12.38QA
Interpretation Introduction

To calculate:

The entropy change for the given reactions using the standard entropies.

Expert Solution & Answer
Check Mark

Answer to Problem 12.38QA

Solution:

a) H2Sg+32 O2g     H2Og  + SO2(g); Srxno=-76.1 J/K

b) 2 SO2g+O2(g)2SO3(g); Srxno=-187.8 J/K

c) SO3g+ H2Ol H2SO4(aq)Srxno=- 306.6 J/K

d) Sg+ O2g SO2(g)Srxno=-124.6 J/K

Explanation of Solution

1) Concept:

Srxno(entropy change for the reaction) can be calculated from the difference between the standard molar entropies of nreactant moles of reactants and the standard molar entropies nproduct moles of products.

2) Formula:

Srxno= nproduct  Sproducto- nreactant  Sreactanto

3) Given:

Substance S0 [J/(mol.K)]
H2Sg 205.6
O2g 205.0
H2Og 188.8
SO2g 248.2
SO3g 256.8
H2Ol 69.9
H2SO4aq 20.1
Sg 167.8

4) Calculations:

a) H2Sg+32 O2g     H2Og  + SO2(g)

The values of standard molar entropies are,

So for H2Sg=205.6 J/mol.K

So for O2g=205.0 J/mol.K

So for H2Og=188.8 J/mol.K

So for SO2g=248.2 J/mol.K

Therefore,

Srxno= nH2Og  SH2Ogo+ nSO2g  SSO2go-n H2Sg  S H2Sgo+n O2g  S O2go

Srxno=1 mol×188.8 J/mol.K+1 mol×248.2 J/mol.K

-1 mol×205.6 J/mol.K+ 32mol×205.0 J/mol.K

Srxno=437 J/K-513.1 J/K

Srxno=-76.1 J/K

The value of Srxno is -76.1 J/K.

b) 2 SO2g+O2(g)2SO3(g)

The values of standard molar entropies are,

So for SO2g=248.2 J/mol.K

So for O2g=205.0 J/mol.K

So for SO3g=256.8 J/mol.K

Srxno= nSO3g  SSO3go- n SO2g  S SO2go+n O2g  S O2go

Srxno=2 mol×256.8 J/mol.K-2 mol×248.2 J/mol.K+1 mol×205.0 J/mol.K

Srxno=513.6 J/K-701.4 J/K

Srxno=-187.8 J/K

The value of Srxno is -187.8 J/K.

c) SO3g+ H2Ol H2SO4(aq)

The values of standard molar entropies are,

So for SO3g=256.8 J/mol.K

So for H2Ol= 69.9 J/mol.K

So for H2SO4aq=20.1 J/mol.K

Srxno= n H2SO4aq  S H2SO4aqo- nSO3g  SSO3go+ nH2Og  SH2Ogo

Srxno=1 mol×20.1 J/mol.K-1 mol×256.8 J/mol.K+1 mol×69.9 J/mol.K

Srxno=20.1J/K-326.7 J/K

Srxno=- 306.6 J/K

The value of Srxno is -306.6 J/K.

d) Sg+ O2g SO2(g)

The values of standard molar entropies are,

So for Sg= 167.8 J/mol.K

So for O2g=205.0 J/mol.K

So for SO2g=248.2 J/mol.K

Srxno= n SO2(g)  S SO2(g)o- nSg  SSgo+ nO2g  SO2go

Srxno=1 mol×248.2 J/mol.K-1 mol×167.8 J/mol.K+1 mol×205.0J/mol.K

Srxno=248.2 J/K-372.8 J/K

Srxno=-124.6 J/K

The value of Srxno is -124.6 J/K.

Conclusion:

Srxno(entropy change for the reaction) can be calculated from the difference between the standard molar entropies of nreactant moles of reactants and the standard molar entropies nproduct moles of products,

Srxno= nproduct  Sproducto- nreactant  Sreactanto

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Chapter 12 Solutions

Chemistry: An Atoms-Focused Approach

Ch. 12 - Prob. 12.13QACh. 12 - Prob. 12.14QACh. 12 - Prob. 12.15QACh. 12 - Prob. 12.16QACh. 12 - Prob. 12.17QACh. 12 - Prob. 12.18QACh. 12 - Prob. 12.19QACh. 12 - Prob. 12.20QACh. 12 - Prob. 12.21QACh. 12 - Prob. 12.22QACh. 12 - Prob. 12.23QACh. 12 - Prob. 12.24QACh. 12 - Prob. 12.25QACh. 12 - Prob. 12.26QACh. 12 - Prob. 12.27QACh. 12 - Prob. 12.28QACh. 12 - Prob. 12.29QACh. 12 - Prob. 12.30QACh. 12 - Prob. 12.31QACh. 12 - Prob. 12.32QACh. 12 - Prob. 12.33QACh. 12 - Prob. 12.34QACh. 12 - Prob. 12.35QACh. 12 - Prob. 12.36QACh. 12 - Prob. 12.37QACh. 12 - Prob. 12.38QACh. 12 - Prob. 12.39QACh. 12 - Prob. 12.40QACh. 12 - Prob. 12.41QACh. 12 - Prob. 12.42QACh. 12 - Prob. 12.43QACh. 12 - Prob. 12.44QACh. 12 - Prob. 12.45QACh. 12 - Prob. 12.46QACh. 12 - Prob. 12.47QACh. 12 - Prob. 12.48QACh. 12 - Prob. 12.49QACh. 12 - Prob. 12.50QACh. 12 - Prob. 12.51QACh. 12 - Prob. 12.52QACh. 12 - Prob. 12.53QACh. 12 - Prob. 12.54QACh. 12 - Prob. 12.55QACh. 12 - Prob. 12.56QACh. 12 - Prob. 12.57QACh. 12 - Prob. 12.58QACh. 12 - Prob. 12.59QACh. 12 - Prob. 12.60QACh. 12 - Prob. 12.61QACh. 12 - Prob. 12.62QACh. 12 - Prob. 12.63QACh. 12 - Prob. 12.64QACh. 12 - Prob. 12.65QACh. 12 - Prob. 12.66QACh. 12 - Prob. 12.67QACh. 12 - Prob. 12.68QACh. 12 - Prob. 12.69QACh. 12 - Prob. 12.70QACh. 12 - Prob. 12.71QACh. 12 - Prob. 12.72QACh. 12 - Prob. 12.73QACh. 12 - Prob. 12.74QACh. 12 - Prob. 12.75QACh. 12 - Prob. 12.76QACh. 12 - Prob. 12.77QACh. 12 - Prob. 12.78QACh. 12 - Prob. 12.79QACh. 12 - Prob. 12.80QACh. 12 - Prob. 12.81QACh. 12 - Prob. 12.82QACh. 12 - Prob. 12.83QACh. 12 - Prob. 12.84QACh. 12 - Prob. 12.85QACh. 12 - Prob. 12.86QA
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