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Ch.19 - Electrochemistry
Tro - Chemistry: A Molecular Approach 4th Edition
Tro4th EditionChemistry: A Molecular ApproachISBN: 9780134112831Not the one you use?Change textbook
All textbooksTro 4th EditionCh.19 - ElectrochemistryProblem 104
Chapter 19, Problem 104

Consider the reaction shown here occurring at 25°C. Cr(s) + Cd2+(aq) → Cr2+(aq) + Cd(s) Determine E°cell, K, and ∆G°rxn for the reaction and complete the table.
[Cd2+] [Cr2+] Q Ecell 𝚫Grxn
1.00 1.00
1.00 1.00 × 10-5
1.00 × 10-5 1.00
4.18 × 10-4 1.00
Table showing concentrations and values for electrochemical cell calculations in electrochemistry.

Verified step by step guidance
1
Step 1: Write the half-reactions for the given redox reaction. For Cr(s) to Cr2+(aq) and Cd2+(aq) to Cd(s).
Step 2: Determine the standard reduction potentials (E°) for each half-reaction from a standard reduction potential table.
Step 3: Calculate the standard cell potential (E°cell) using the formula E°cell = E°cathode - E°anode.
Step 4: Calculate the reaction quotient (Q) for each set of concentrations using the formula Q = [products]/[reactants].
Step 5: Use the Nernst equation to calculate the cell potential (Ecell) for each set of concentrations: Ecell = E°cell - (RT/nF) * ln(Q).

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Key Concepts

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

Electrochemical Cell

An electrochemical cell is a device that converts chemical energy into electrical energy through redox reactions. It consists of two electrodes, an anode where oxidation occurs, and a cathode where reduction takes place. The flow of electrons from the anode to the cathode generates an electric current, which can be harnessed for work.

Nernst Equation

The Nernst equation relates the cell potential (E) of an electrochemical cell to the standard cell potential (E°) and the reaction quotient (Q). It is expressed as E = E° - (RT/nF)ln(Q), where R is the gas constant, T is the temperature in Kelvin, n is the number of moles of electrons transferred, and F is Faraday's constant. This equation allows for the calculation of cell potential under non-standard conditions.
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Gibbs Free Energy (ΔGrxn)

Gibbs free energy (ΔGrxn) is a thermodynamic quantity that indicates the spontaneity of a reaction. It is defined as ΔGrxn = ΔH - TΔS, where ΔH is the change in enthalpy, T is the temperature in Kelvin, and ΔS is the change in entropy. A negative ΔGrxn indicates a spontaneous reaction, while a positive value suggests non-spontaneity. The relationship between ΔGrxn and cell potential (Ecell) is given by ΔGrxn = -nFEcell.
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