Chapter 19, Problem 19.104QP

(a)

Interpretation Introduction

Interpretation:

The reason why gold is not tarnished by oxygen has to be explained and the nature of spontaneity of the given reaction has to be predicted.  The probable reaction between gold and fluorine also has to be predicted.

Concept Introduction:

Tarnishing of metals: Tarnish is a layer of oxide that is formed on the surface of metals.

The surface of the metal is highly energetic.  In order to reduce energy the metal in its native state will react with the atmospheric oxide and forms a layer of oxide in the surface.  Only if the reduction potential of oxygen is sufficiently positive, the metal can be reduced to its oxide.

Spontaneous process: In thermodynamics a process is spontaneous if it is taking place by itself without the help of external energy. All spontaneous process will have highly energetic initial state than the final state. This indicates that while the process occurs, there is a decrease in free energy of the system.

The standard electrode potential of a cell ${\text{(E}}^{°}{}_{\text{cell}})$ is the difference in electrode potential of the cathode and anode.

  ${\text{E}}^{\text{°}}{}_{\text{cell}}={\text{E}}^{\text{°}}{}_{\text{cathode}}-{\text{E}}^{\text{°}}{}_{\text{anode}}$

The relation between Gibbs free energy and cell potential: The amount of energy in a system that can be converted into useful energy is defined as free energy in thermodynamics. 

Free energy and the cell potential is related by the given equation.

  $\text{ΔG=-nFE}$

Where,

  $\text{ΔG}$ is the change in free energy

  $\text{n}$ is the number of electrons transferred

  $\text{F}$ is the Faraday constant $\text{(F}={\text{96500Cmol}}^{\text{-1}})$

  $\text{E}$ is the cell potential

(b)

Interpretation Introduction

Interpretation:

The reason why gold is not tarnished by oxygen has to be explained and the nature of spontaneity of the given reaction has to be predicted.  The probable reaction between gold and fluorine also has to be predicted.

Concept Introduction:

Tarnishing of metals: Tarnish is a layer of oxide that is formed on the surface of metals.

The surface of the metal is highly energetic.  In order to reduce energy the metal in its native state will react with the atmospheric oxide and forms a layer of oxide in the surface.  Only if the reduction potential of oxygen is sufficiently positive, the metal can be reduced to its oxide.

Spontaneous process: In thermodynamics a process is spontaneous if it is taking place by itself without the help of external energy. All spontaneous process will have highly energetic initial state than the final state. This indicates that while the process occurs, there is a decrease in free energy of the system.

The standard electrode potential of a cell ${\text{(E}}^{°}{}_{\text{cell}})$ is the difference in electrode potential of the cathode and anode.

  ${\text{E}}^{\text{°}}{}_{\text{cell}}={\text{E}}^{\text{°}}{}_{\text{cathode}}-{\text{E}}^{\text{°}}{}_{\text{anode}}$

The relation between Gibbs free energy and cell potential: The amount of energy in a system that can be converted into useful energy is defined as free energy in thermodynamics. 

Free energy and the cell potential is related by the given equation.

  $\text{ΔG=-nFE}$

Where,

  $\text{ΔG}$ is the change in free energy

  $\text{n}$ is the number of electrons transferred

  $\text{F}$ is the Faraday constant $\text{(F}={\text{96500Cmol}}^{\text{-1}})$

  $\text{E}$ is the cell potential

(c)

Interpretation Introduction

Interpretation:

The reason why gold is not tarnished by oxygen has to be explained and the nature of spontaneity of the given reaction has to be predicted.  The probable reaction between gold and fluorine also has to be predicted.

Concept Introduction:

Tarnishing of metals: Tarnish is a layer of oxide that is formed on the surface of metals.

The surface of the metal is highly energetic.  In order to reduce energy the metal in its native state will react with the atmospheric oxide and forms a layer of oxide in the surface.  Only if the reduction potential of oxygen is sufficiently positive, the metal can be reduced to its oxide.

Spontaneous process: In thermodynamics a process is spontaneous if it is taking place by itself without the help of external energy. All spontaneous process will have highly energetic initial state than the final state. This indicates that while the process occurs, there is a decrease in free energy of the system.

The standard electrode potential of a cell ${\text{(E}}^{°}{}_{\text{cell}})$ is the difference in electrode potential of the cathode and anode.

  ${\text{E}}^{\text{°}}{}_{\text{cell}}={\text{E}}^{\text{°}}{}_{\text{cathode}}-{\text{E}}^{\text{°}}{}_{\text{anode}}$

The relation between Gibbs free energy and cell potential: The amount of energy in a system that can be converted into useful energy is defined as free energy in thermodynamics. 

Free energy and the cell potential is related by the given equation.

  $\text{ΔG=-nFE}$

Where,

  $\text{ΔG}$ is the change in free energy

  $\text{n}$ is the number of electrons transferred

  $\text{F}$ is the Faraday constant $\text{(F}={\text{96500Cmol}}^{\text{-1}})$

  $\text{E}$ is the cell potential