Chemistry: The Central Science (14th Edition)
Chemistry: The Central Science (14th Edition)
14th Edition
ISBN: 9780134414232
Author: Theodore E. Brown, H. Eugene LeMay, Bruce E. Bursten, Catherine Murphy, Patrick Woodward, Matthew E. Stoltzfus
Publisher: PEARSON
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Chapter 8, Problem 1DE
Interpretation Introduction

Interpretation:

The facts related to the resonance stabilization of benzene, heat of hydrogenation and fuel value of benzene and acetylene are to be determined; also the experiment to prove the existence of resonance in cyclooctatetraene is to be determined.

Concept Introduction:

The enthalpy change of the combustion reaction is calculated by the difference of sum of the enthalpy change of products and reactants.

(a)

To determine:

The comparison of heat of hydrogenation of benzene and acetylene and the greater fuel value out of 1.0mol benzene and 3.0mol acetylene; also the explanation of stability of benzene on the basis of these calculations.

Expert Solution
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Explanation of Solution

The heat of hydrogenation of acetylene is 1299.53kJ/mol and the fuel value of 3.0mol acetylene is 149.73kJ/g.

The heat of hydrogenation of benzene is 3301.39kJ/mol and the fuel value of benzene is 42.29kJ/g.

The fuel value of acetylene is higher than benzene which is consistent with the stability of benzene.

Interpretation Introduction

Step 1:

To determine:

The heat of hydrogenation and fuel value of 3.0mol acetylene.

Expert Solution
Check Mark

Answer to Problem 1DE

Solution:

The heat of hydrogenation of acetylene is 1299.53kJ/mol and the fuel value of 3.0mol acetylene is 149.73kJ/g.

Explanation of Solution

The balanced chemical equation for the combustion of acetylene is,

C2H2(g)+52O2(g)2CO2(g)+H2O(l)

The enthalpy change of the given reaction is calculated by the formula,

ΔH=nΔH(products)mΔH(reactants)=(2ΔHCO2(g)+ΔHH2O(l))(ΔHC2H2(g)+52ΔHO2(g))

Substitute the values of ΔHCO2(g), ΔHH2O(l), ΔHC2H2(g) and ΔHO2(g) from appendix C in equation.

ΔH0=(2×393.5kJ/mol+1×285.83kJ/mol)(1×226.7kJ/mol+52×0.0kJ/mol)=1299.53kJ/mol

The fuel value of acetylene is calculated by dividing its standard enthalpy change by the mass.

FuelvalueofC2H2=1299.53kJ/mol26.036g/mol×3.0mol=149.73kJ/g

Interpretation Introduction

Step 2:

To determine:

The heat of hydrogenation and fuel value of 1.0mol benzene.

Expert Solution
Check Mark

Answer to Problem 1DE

Solution:

The heat of hydrogenation of benzene is 3301.39kJ/mol and the fuel value of benzene is 42.29kJ/g.

Explanation of Solution

The balanced chemical equation for the combustion of benzene is,

C6H6(g)+152O2(g)6CO2(g)+3H2O(l)

The enthalpy change of the given reaction is calculated by the formula,

ΔH=nΔH(products)mΔH(reactants)=(6ΔHCO2(g)+3ΔHH2O(l))(ΔHC6H6(l)+152ΔHO2(g))

Substitute the values of ΔHCO2(g), ΔHH2O(l), ΔHCH4(g) and ΔHO2(g) from appendix C in equation.

ΔH0=(6×393.5kJ/mol+3×285.83kJ/mol)(1×82.9kJ/mol+152×0.0kJ/mol)=3301.39kJ/mol

The fuel value of benzene is calculated by dividing its standard enthalpy change by the mass.

FuelvalueofC6H6=3301.39kJ/mol78.06g/mol×1.0mol=42.29kJ/g

Since, the fuel value of benzene is less than that of acetylene. Therefore, benzene ring is especially stable and not gets easily oxidized. Thus, the calculations of heat of hydrogenation and fuel value are consistent with the extra stabilization of benzene.

Conclusion

The heat of hydrogenation of acetylene is 1299.53kJ/mol and the fuel value of 3.0mol acetylene is 149.73kJ/g.

The heat of hydrogenation of benzene is 3301.39kJ/mol and the fuel value of benzene is 42.29kJ/g.

The fuel value of acetylene is higher than benzene which is consistent with the stability of benzene.

Interpretation Introduction

(b)

To determine:

The heat of hydrogenation and fuel value of toluene.

Expert Solution
Check Mark

Answer to Problem 1DE

Solution:

The heat of hydrogenation of toluene is 3461.82kJ/mol and the fuel value of toluene is 37.57kJ/g.

Explanation of Solution

The balanced chemical equation for the combustion of benzene is,

C6H5CH3(g)+8O2(g)6CO2(g)+4H2O(l)

The enthalpy change of the given reaction is calculated by the formula,

ΔH=nΔH(products)mΔH(reactants)=(6ΔHCO2(g)+4ΔHH2O(l))(ΔHC6H5CH3(g)+8ΔHO2(g))

Substitute the values of ΔHCO2(g), ΔHH2O(l), ΔHC6H5CH3(g) and ΔHO2(g) from appendix C in equation.

ΔH0=(6×393.5kJ/mol+4×285.83kJ/mol)(1×42.5kJ/mol+6×0.0kJ/mol)=3461.82kJ/mol

The fuel value of benzene is calculated by dividing its standard enthalpy change by the mass.

FuelvalueofC6H6=3461.82kJ/mol92.14g/mol=37.57kJ/g

Conclusion

The heat of hydrogenation of toluene is 3461.82kJ/mol and the fuel value of toluene is 37.57kJ/g.

Interpretation Introduction

(c)

To determine:

The explanation of stabilization of benzene by using the given values of heat of hydrogenation.

Expert Solution
Check Mark

Answer to Problem 1DE

Solution:

The heat of hydrogenation for benzene is more than cyclohexane because benzene is more stable and it requires more energy to break its bonds.

Explanation of Solution

Given

The heat of hydrogenation of benzene to make cyclohexane is 208kJ/mol.

The heat of hydrogenation of cyclohexene to make cyclohexane is 120kJ/mol.

The heat of hydrogenation is the energy required to break the carbon-hydrogen bonds in the molecule. More is the heat of hydrogenation; more is the stability of the molecule. Since, the heat of hydrogenation of benzene is more than that of the cyclohexene. Therefore, the benzene is more stable than that of the cyclohexene.

Conclusion

The heat of hydrogenation for benzene is more than cyclohexane because benzene is more stable and it requires more energy to break its bonds.

Interpretation Introduction

(d)

To determine:

The explanation of resonance and stability of benzene on the basis of bond lengths and bond angles.

Expert Solution
Check Mark

Answer to Problem 1DE

Solution:

The bond lengths and bond angle in benzene are all equal which confirms the existence of phenomenon of resonance in the molecule.

Explanation of Solution

The pi electrons present in the benzene ring is delocalized among all the carbon atoms of the ring. Due to this the bond lengths and bond angles of all carbon-carbon bonds are equal which proves the delocalized bonding in the ring. Therefore, the bond lengths and bond angles are sufficient to decide the existence of resonance and stability in the structure.

Conclusion

The bond lengths and bond angle in benzene are all equal which confirms the existence of phenomenon of resonance in the molecule.

Interpretation Introduction

(e)

To determine:

The experiment to prove the existence of resonance in cyclo octatetraene.

Expert Solution
Check Mark

Answer to Problem 1DE

Solution:

The NMR spectrum of cyclo octatetraene proves that this molecule does not exhibit the phenomenon of resonance.

Explanation of Solution

The NMR spectrum of the given sample is the measure of number of hydrogen nuclei in the molecule. The number of peaks present in the NMR spectrum decides the types of nucleus present in the structure. The given structure of cyclooctatetraene contains two types of protons present in the structure having two different bond lengths. Therefore, the pheneomenon of resonance does not exhibit in this structure.

Conclusion

The NMR spectrum of cyclooctatetraene proves that this molecule does not exhibit the phenomenon of resonance.

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Chapter 8 Solutions

Chemistry: The Central Science (14th Edition)

Ch. 8.5 - Which of the these molecules has a Lewis structure...Ch. 8.5 - How many valence electrons should appear in the...Ch. 8.5 - Compare the lewis symbol for neon the structure...Ch. 8.5 - Prob. 8.7.2PECh. 8.5 - Prob. 8.8.1PECh. 8.5 - Prob. 8.8.2PECh. 8.5 - Prob. 8.9.1PECh. 8.5 - Prob. 8.9.2PECh. 8.6 - Which of the statements about resonance is true?...Ch. 8.6 - Prob. 8.10.2PECh. 8.7 - Prob. 8.11.1PECh. 8.7 - Prob. 8.11.2PECh. 8 - Prob. 1DECh. 8 - Prob. 1ECh. 8 - Prob. 2ECh. 8 - A portion of a two-dimensional "slab" of NaCl(s)...Ch. 8 - Prob. 4ECh. 8 - Prob. 5ECh. 8 - Incomplete Lewis structures for the nitrous acid...Ch. 8 - Prob. 7ECh. 8 - Prob. 8ECh. 8 - Prob. 9ECh. 8 - True or false: The hydrogen atom is most stable...Ch. 8 - Consider the element silicon, Si. Write its...Ch. 8 - Write the electron configuration for the element...Ch. 8 - Prob. 13ECh. 8 - What is the Lewis symbol for each of the following...Ch. 8 - Using Lewis symbols, diagram the reaction between...Ch. 8 - Use Lewis symbols to represent the reaction that...Ch. 8 - Predict the chemical formula of the ionic compound...Ch. 8 - Prob. 18ECh. 8 - Prob. 19ECh. 8 - Prob. 20ECh. 8 - Is lattice energy usually endothermic or...Ch. 8 - NaCI and KF have the same crystal structure. The...Ch. 8 - Prob. 23ECh. 8 - Prob. 24ECh. 8 - Consider the ionic compounds KF, NaCl, NaBr, and...Ch. 8 - Which of the following trends in lattice energy is...Ch. 8 - Energy is required to remove two electrons from Ca...Ch. 8 - Prob. 28ECh. 8 - Use data from Appendix C, Figure 7.10, and Figure...Ch. 8 - Prob. 30ECh. 8 - Prob. 31ECh. 8 - Prob. 32ECh. 8 - Using Lewis symbols and Lewis structures, diagram...Ch. 8 - Use Lewis symbols and Lewis structures to diagram...Ch. 8 - Prob. 35ECh. 8 - Prob. 36ECh. 8 - Prob. 37ECh. 8 - What is the trend in electronegativity going from...Ch. 8 - Prob. 39ECh. 8 - By referring only to the periodic table, select...Ch. 8 - which of the following bonds are polar? B-F,...Ch. 8 - Arrange the bonds in each of the following sets in...Ch. 8 - Prob. 43ECh. 8 - Prob. 44ECh. 8 - In the following pairs of binary compounds,...Ch. 8 - Prob. 46ECh. 8 - Prob. 47ECh. 8 - Write Lewis structures for the following: H2CO...Ch. 8 - Prob. 49ECh. 8 - Draw the dominant Lewis structure for the...Ch. 8 - Write Lewis structures that obey the octet rule...Ch. 8 - Prob. 52ECh. 8 - Prob. 53ECh. 8 - Prob. 54ECh. 8 - Prob. 55ECh. 8 - Prob. 56ECh. 8 - Prob. 57ECh. 8 - Prob. 58ECh. 8 - Prob. 59ECh. 8 - Prob. 60ECh. 8 - Prob. 61ECh. 8 - 8.62 For Group 3A-7A elements in the third row of...Ch. 8 - Draw the Lewis structures for each of the...Ch. 8 - Prob. 64ECh. 8 - In the vapor phase, BeCl2exists as a discrete...Ch. 8 - 8.66 Describe the molecule xenon trioxide, XeO3,...Ch. 8 - 8.67 There are many Lewis structures you could...Ch. 8 - Prob. 68ECh. 8 - Using Table 8.3, estimate H for each of the...Ch. 8 - Using Table 8.3, estimate H for the following...Ch. 8 - State whether each of these statements is true or...Ch. 8 - Prob. 72ECh. 8 - Prob. 73ECh. 8 - Prob. 74ECh. 8 - Prob. 75ECh. 8 - Prob. 76ECh. 8 - A new compound is made that has a C-C bond length...Ch. 8 - A new compound is made that has an N-N bond length...Ch. 8 - Prob. 79AECh. 8 - Prob. 80AECh. 8 - An ionic substance of formula MX has a lattice...Ch. 8 - Prob. 82AECh. 8 - Prob. 83AECh. 8 - Prob. 84AECh. 8 - Consider the collection of nonmetallic elements 0,...Ch. 8 - The substance chlorine monoxide, CIO(g), is...Ch. 8 - [8.87] a. using the electronegativities of Br...Ch. 8 - Prob. 88AECh. 8 - Although I3- is a known ion, F3- is not. a. Draw...Ch. 8 - Calculate the formal charge on the indicated atom...Ch. 8 - The hypochlorite ion, CIO- , is the active...Ch. 8 - Prob. 92AECh. 8 - a. Triazine, C3 H3N3, is like benzene except that...Ch. 8 - Prob. 94IECh. 8 - Prob. 95IECh. 8 - Prob. 96IECh. 8 - Prob. 97IECh. 8 - Prob. 98IECh. 8 - Prob. 99IECh. 8 - Prob. 100IECh. 8 - Prob. 101IECh. 8 - Prob. 102IECh. 8 - 8.103 The compound chloral hydrate, known in...Ch. 8 - Barium azide is 62.04% Ba and 37.96% N. Each azide...Ch. 8 - Acetylene (C2H2) and nitrogen (N2) both contain a...Ch. 8 - Prob. 106IECh. 8 - Prob. 107IECh. 8 - 8.108 Formic acid has the chemical formula...Ch. 8 - Prob. 109IECh. 8 - Prob. 110IE
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