   Chapter 19, Problem 99GQ

Chapter
Section
Textbook Problem

Iron(II) ion undergoes a disproportionation reaction to give Fe(s) and the iron(III) ion. That is, iron(II) ion is both oxidized and reduced within the same reaction.3 Fe2+(aq) ⇄ Fe(s) + 2 Fe3+(aq) (a) What two half-reactions make up the disproportionation reaction? (b) Use the values of the standard reduction potentials for the two half-reactions in part (a) to determine whether this disproportionation reaction is product-favored at equilibrium. (c) What is the equilibrium constant for this reaction?

(a)

Interpretation Introduction

Interpretation:

The two half reactions which make up the disproportination reaction has to be determined.

Concept introduction:

Voltaic cell or Galvanic cell:

The device to produce electricity by using chemical reactions. In these divces are redox chemical reactions are occured.

A voltaic cell converts chemical energy into electrical energy.

It consists of two half cells. Each half cell consists of a metal and a solution of a salt of metal. Two half cells are connected by salt bridge.

The chemical reaction in the half cell is an oxidation reduction (redox)reactions.

For example:

Cell diagram of voltaic or galvanic cell is as follows.

Salt bridge                        Cu(s)|Cu2+(aq)  ||  Ag+(aq)|Ag(s)____________     ___________                                       Half cell             Half cell

According to the first law of thermodynamics, the change in internal energy of a system is equal ti the heat added to the sysytem minus the work done by the system.

Explanation

From the given information, Iron (II) ion undergoes a disproportionaion reaction to give Fe(s) and the iron(III) ion. That is iron (II) ion as both oxidized and reduced within the same reaction.

The half reactions are as follows.

Fe2+(aq) + 2e- Fe (s)2Fe2+(aq) 2Fe3+(aq) + 2e-

By adding these two reactions we get , overall reaction.

Fe2+(aq) + 2e- Fe

(b)

Interpretation Introduction

Interpretation:

It has to be identified whether the disproportination reaction is a product-favored at equilibrium or not using the standard reduction potentials.

Concept introduction:

Voltaic cell or Galvanic cell:

The device to produce electricity by using chemical reactions. In these divces are redox chemical reactions are occured.

A voltaic cell converts chemical energy into electrical energy.

It consists of two half cells. Each half cell consists of a metal and a solution of a salt of metal. Two half cells are connected by salt bridge.

The chemical reaction in the half cell is an oxidation reduction (redox)reactions.

For example:

Cell diagram of voltaic or galvanic cell is as follows.

Salt bridge                        Cu(s)|Cu2+(aq)  ||  Ag+(aq)|Ag(s)____________     ___________                                       Half cell             Half cell

According to the first law of thermodynamics, the change in internal energy of a system is equal ti the heat added to the sysytem minus the work done by the system.

The equation is as follows.

ΔU = Q - WΔU = Change in internal energyQ = Heat added to the systemW=Work done by the system

In voltaic cell, the maximum cell potential is directly related to the free energy difference between the reactants and products in the cell.

ΔG0= -nFE0n = Number of moles transferred per mole of reactant and productsF = Faradayconstant=96485C/mol  E0= Volts = Work(J)/Charge(C)

The relation between standard cell potential and equilibrium constant is as follows.

lnK = nE00.0257 at 298K

(c)

Interpretation Introduction

Interpretation:

The equilbrium constant of the reaction has to be calculated.

Concept introduction:

According to the first law of thermodynamics, the change in internal energy of a system is equal ti the heat added to the sysytem minus the work done by the system.

The equation is as follows.

ΔU = Q - WΔU = Change in internal energyQ = Heat added to the systemW=Work done by the system

In voltaic cell, the maximum cell potential is directly related to the free energy difference between the reactants and products in the cell.

ΔG0= -nFE0n = Number of moles transferred per mole of reactant and productsF = Faradayconstant=96485C/mol  E0= Volts = Work(J)/Charge(C)

The relation between standard cell potential and equilibrium constant is as follows.

lnK = nE00.0257 at 298K

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