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Ch.19 - Electrochemistry
McMurry - Chemistry 8th Edition
McMurry8th EditionChemistryISBN: 9781292336145Not the one you use?Change textbook
All textbooksMcMurry 8th EditionCh.19 - ElectrochemistryProblem 162b
Chapter 19, Problem 162b

The half-reactions that occur in ordinary alkaline batteries can be written as In 1999, researchers in Israel reported a new type of alkaline battery, called a 'super-iron' battery. This battery uses the same anode reaction as an ordinary alkaline battery but involves the reduction of FeO42- ion (from K2FeO4) to solid Fe(OH)3 at the cathode. (b) Write a balanced equation for the cathode half-reaction in a super-iron battery. The half-reaction occurs in a basic environment.

Verified step by step guidance
1
Identify the species involved in the cathode half-reaction: FeO_4^{2-} is reduced to Fe(OH)_3.
Write the unbalanced half-reaction: FeO_4^{2-} \(\rightarrow\) Fe(OH)_3.
Balance the iron atoms: FeO_4^{2-} \(\rightarrow\) Fe(OH)_3 already has one Fe on each side.
Balance the oxygen atoms by adding water molecules: FeO_4^{2-} + 3H_2O \(\rightarrow\) Fe(OH)_3 + 4OH^-.
Balance the charge by adding electrons: FeO_4^{2-} + 3H_2O + 3e^- \(\rightarrow\) Fe(OH)_3 + 4OH^- to ensure both sides have the same charge.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Half-Reactions

Half-reactions are the individual oxidation or reduction processes that occur in an electrochemical cell. In a battery, the anode undergoes oxidation, while the cathode undergoes reduction. Understanding half-reactions is crucial for balancing redox reactions, as they allow us to separate the electron transfer processes and identify the species involved.

Basic Environment

A basic environment refers to a solution with a pH greater than 7, where hydroxide ions (OH-) are present. In such conditions, reactions may involve the formation of hydroxides or the consumption of protons. Recognizing the implications of a basic environment is essential for accurately writing and balancing half-reactions, particularly in alkaline batteries.

Balancing Redox Reactions

Balancing redox reactions involves ensuring that both mass and charge are conserved in the overall reaction. This process typically includes balancing the number of electrons transferred, as well as the atoms involved in the oxidation and reduction processes. Mastery of this concept is vital for writing correct half-reactions, especially when dealing with complex species like FeO4^2-.
Related Practice
Textbook Question

The half-reactions that occur in ordinary alkaline batteries can be written as In 1999, researchers in Israel reported a new type of alkaline battery, called a 'super-iron' battery. This battery uses the same anode reaction as an ordinary alkaline battery but involves the reduction of FeO42- ion (from K2FeO4) to solid Fe(OH)3 at the cathode. (a) Use the following standard reduction potential and any data from Appendixes C and D to calculate the standard cell potential expected for an ordinary alkaline battery:

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Textbook Question

Experimental solid-oxide fuel cells that use butane (C4H10) as the fuel have been reported recently. These cells contain composite metal/metal oxide electrodes and a solid metal oxide electrolyte. The cell half-reactions are (b) Use the thermodynamic data in Appendix B to calculate the values of E° and the equilibrium constant K for the cell reaction at 25 °C. Will E° and K increase, decrease, or remain the same on raising the temperature?

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Textbook Question

We've said that the +1 oxidation state is uncommon for indium but is the most stable state for thallium. Verify this statement by calculating E ° and ΔG ° (in kilojoules) for the disproportionation reaction

3 M+1aq2S M3+1aq2 + 2 M1s2 M = In or Tl

Is disproportionation a spontaneous reaction for In+ and/orTl+? Standard reduction potentials for the relevant halfreactions are

In3+1aq2 + 2 e- S In+1aq2 E° = -0.44 V

In+1aq2 + e- S In1s2 E° = -0.14 V

Tl3+1aq2 + 2 e- S Tl+1aq2 E° = +1.25 V

Tl+1aq2 + e- S Tl1s2 E° = -0.34 V

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Textbook Question
The nickel–iron battery has an iron anode, an NiO(OH) cathode, and a KOH electrolyte. This battery uses the follow-ing half-reactions and has an E° value of 1.37 V at 25 °C. (b) Calculate ∆G° (in kilojoules) and the equilibrium con-stant K for the cell reaction at 25 °C.
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Textbook Question

The half-reactions that occur in ordinary alkaline batteries can be written as In 1999, researchers in Israel reported a new type of alkaline battery, called a 'super-iron' battery. This battery uses the same anode reaction as an ordinary alkaline battery but involves the reduction of FeO42- ion (from K2FeO4) to solid Fe(OH)3 at the cathode. (c) A super-iron battery should last longer than an ordinary alkaline battery of the same size and weight because its cathode can provide more charge per unit mass. Quan-titatively compare the number of coulombs of charge released by the reduction of 10.0 g K2FeO4 to Fe(OH)3 with the number of coulombs of charge released by the reduction 10.0 g of MnO2 to MnO(OH).

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Textbook Question
Consider the redox titration of 100.0 mL of a solution of 0.010 M Fe2+ in 1.50 M H2SO4 with a 0.010 M solution of KMnO4, yielding Fe3+ and Mn2+. The titration is carried out in an electrochemical cell equipped with a platinum electrode and a calomel reference electrode consisting of an Hg2Cl2/Hg electrode in contract with a saturated KCl solution having [Cl-] = 2.9M. Using any data in Appendixes C and D, calculate the cell potential after addition of (a) 5.0 mL, (b) 10.0mL, (c) 19.0 mL, and (d) 21.0 mL of the KMnO4 solution.
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