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Chapter 7: Problem 93

In the chemical process called electron transfer, an electron is transferred from one atom or molecule to another. (We will talk about electron transfer extensively in Chapter 20.) A simple electron transfer reaction is $$ \mathrm{A}(g)+\mathrm{A}(g) \longrightarrow \mathrm{A}^{+}(g)+\mathrm{A}^{-}(g) $$ In terms of the ionization energy and electron affinity of atom A, what is the energy change for this reaction? For a representative nonmetal such as chlorine, is this process exothermic? For a representative metal such as sodium, is this process exothermic?

Short Answer

Expert verified
The energy change for the given electron transfer reaction can be calculated as: Energy change = Ionization energy of A - Electron affinity of A. For chlorine (a representative nonmetal), the process is endothermic with an energy change of 1600 kJ/mol. For sodium (a representative metal), the process is also endothermic with an energy change of 549 kJ/mol. Therefore, the process is not exothermic for both chlorine and sodium.

Step by step solution

01

Define ionization energy and electron affinity

Ionization energy is the energy required to remove an electron from an atom in its gaseous state. Electron affinity is the energy change that occurs when an electron is added to an atom in its gaseous state.
02

Calculate the energy change for the electron transfer reaction

The energy change for the reaction can be determined by considering the ionization energy and electron affinity: Energy change = Ionization energy of A - Electron affinity of A
03

Determine if the process is exothermic for a representative nonmetal (chlorine)

For chlorine (a representative nonmetal), the ionization energy is 1251 kJ/mol and the electron affinity is -349 kJ/mol. Using the energy change equation, we can calculate the energy change for the electron transfer reaction: Energy change = 1251 kJ/mol - (-349 kJ/mol) = 1600 kJ/mol Since the energy change is positive, the process is endothermic for chlorine, not exothermic.
04

Determine if the process is exothermic for a representative metal (sodium)

For sodium (a representative metal), the ionization energy is 496 kJ/mol and the electron affinity is -53 kJ/mol. Using the energy change equation, we can calculate the energy change for the electron transfer reaction: Energy change = 496 kJ/mol - (-53 kJ/mol) = 549 kJ/mol Since the energy change is positive, the process is also endothermic for sodium, not exothermic. In conclusion, the energy change for the electron transfer reaction can be calculated using the ionization energy and electron affinity of atom A. The process is endothermic for both a representative nonmetal (chlorine) and a representative metal (sodium), meaning the process is not exothermic for these examples.

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