
Interpretation:
The energy change for the given reaction is to be calculated.
Concept introduction:
Ionization energy is the energy required when an electron is removed from a gaseous atom.

Answer to Problem 86AP
Solution:
(a) 225 kJ/mol
(b) 168 kJ/mol
(c) 70 kJ/mol
(a)
Explanation of Solution
Given information: The reaction is as follows:
Li(g)+I(g)→Li +(g)+I−(g)
The given reaction is as follows:
Li(g)+I(g)→Li +(g)+I−(g)
In this reaction, lithium loses an electron whereas iodine gains an electron.
With reference tofigure 7.8,
The ionization energy of lithium is 520 kJ/mol
Li(g)→Li +(g)+e− ΔH°=520 kJ/mol…… (1)
With reference tofigure 7.10,
The electron affinity of iodine is −295 kJ/mol
I(g)+e−→I−(g) ΔH°=−295 kJ/mol…… (2)
Add equations(1) and (2) as follows:
Li(g)→Li +(g)+e− ΔH°=520 kJ/molI(g)+e−→I-(g) ΔH°=−295 kJ/mol¯Li(g)+I(g)→¯Li +(g)+I-(g) ¯ΔH°=225 kJ/mol
Therefore, the energy change for the reactionis 225 kJ/mol.
(b)
Given information: The reaction is as follows:
Na(g)+F(g)→Na +(g)+F−(g)
The given reaction is as follows:
Na(g)+F(g)→Na +(g)+F−(g)
In this reaction, sodium loses an electron whereas fluorine gains an electron.
With referencetofigure 7.8,
The ionization energy of sodium is 496 kJ/mol
Na(g)→Na +(g)+e− ΔH°=496 kJ/mol…… (3)
With referencetofigure 7.10,
The electron affinity of fluorine is −328 kJ/mol
F(g)+e−→F−(g) ΔH°=−328 kJ/mol…… (4)
Add equation (3) and (4) as follows:
Na(g)→Na +(g)+e− ΔH°=496 kJ/molF(g)+e−→F−(g) ΔH°=−328 kJ/mol¯Na(g)+F(g)→¯Na +(g)+F−(g) ¯ΔH°=168 kJ/mol
Therefore, the energy change for the reaction is 168 kJ/mol.
(c)
Given information: The reaction is as follows:
K(g)+Cl(g)→K+(g)+Cl−(g)
The given reaction is as follows:
K(g)+Cl(g)→K+(g)+Cl−(g)
In the above reaction, potassium loses an electron whereas chlorine gains an electron.
With referencetofigure 7.8,
The ionization energy of lithium is 419 kJ/mol
K(g)→K+(g)+e− ΔH°=419 kJ/mol…… (5)
With referencetofigure 7.10,
The electron affinity of iodine is −349 kJ/mol
Cl(g)+e−→Cl−(g) ΔH°=−349 kJ/mol…… (6)
Add equations(5) and (6) as follows:
K(g)→K+(g)+e− ΔH°=419 kJ/molCl(g)+e−→Cl−(g) ΔH°=−349 kJ/mol¯K(g)+Cl(g)→¯K+(g)+Cl−(g) ¯ΔH°=70 kJ/mol
Therefore, the energy change for the reaction is 70 kJ/mol.
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Chapter 8 Solutions
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- Chemistry: The Molecular ScienceChemistryISBN:9781285199047Author:John W. Moore, Conrad L. StanitskiPublisher:Cengage Learning
