A voltaic cell is constructed that uses the following half-cell reactions:
Cu⁺(aq) + e^- → Cu(s)
I₂(s) + 2 e^- → 2 I^-(aq)
The cell is operated at 298 K with [Cu⁺] = 0.25 M and [I^-] = 0.035 M.
(a) Determine E for the cell at these concentrations.

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Identify the oxidation and reduction half-reactions. In this case, Cu+ is reduced to Cu(s) and I2(s) is oxidized to I-.

Write the balanced overall cell reaction by combining the half-reactions. Ensure that the number of electrons lost in oxidation equals the number of electrons gained in reduction.

Use the Nernst equation to calculate the cell potential (E) at non-standard conditions. The Nernst equation is: E = E^0 - (RT/nF) * ln(Q), where E^0 is the standard cell potential, R is the gas constant (8.314 J/mol·K), T is the temperature in Kelvin, n is the number of moles of electrons transferred, F is the Faraday constant (96485 C/mol), and Q is the reaction quotient.

Calculate the reaction quotient, Q, from the given concentrations. For the reaction Cu+ + I2 -> Cu + 2 I-, Q is calculated as Q = [I-]^2 / [Cu+].

Substitute the values of E^0, R, T, n, F, and Q into the Nernst equation to find the cell potential E.

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주요 개념

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Electrochemical Cells

Electrochemical cells, such as voltaic cells, convert chemical energy into electrical energy through redox reactions. In a voltaic cell, oxidation occurs at the anode and reduction at the cathode, allowing for the flow of electrons through an external circuit. Understanding the setup and function of these cells is crucial for analyzing their behavior under different conditions.

Nernst Equation

The Nernst equation relates the cell potential (E) to the concentrations of the reactants and products in a redox reaction. It is expressed as E = E° - (RT/nF) ln(Q), where E° is the standard cell potential, R is the gas constant, T is the temperature in Kelvin, n is the number of moles of electrons transferred, F is Faraday's constant, and Q is the reaction quotient. This equation is essential for calculating the cell potential under non-standard conditions.

Reaction Quotient (Q)

The reaction quotient (Q) is a measure of the relative concentrations of reactants and products at any point in a reaction. It is calculated using the formula Q = [products]/[reactants], with each concentration raised to the power of its stoichiometric coefficient. In the context of the Nernst equation, Q helps determine how the cell potential changes as the reaction progresses and concentrations vary.

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교과서 질문

Gold exists in two common positive oxidation states, +1 and +3. The standard reduction potentials for these oxidation states are Au+1aq2 + e- ¡ Au1s2 Ered ° = +1.69 V Au3+1aq2 + 3 e- ¡ Au1s2 Ered ° = +1.50 V (c) Miners obtain gold by soaking gold-containing ores in an aqueous solution of sodium cyanide. A very soluble complex ion of gold forms in the aqueous solution because of the redox reaction 4 Au1s2 + 8 NaCN1aq2 + 2 H2O1l2 + O21g2 ¡ 4 Na3Au1CN2241aq2 + 4 NaOH1aq2 What is being oxidized, and what is being reduced in this reaction?

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교과서 질문

(b) Given the following reduction potentials, calculate the standard emf of the cell: Cd1OH221s2 + 2 e- ¡ Cd1s2 + 2 OH-1aq2 E°red = -0.76 V NiO1OH21s2 + H2O1l2 + e- ¡ Ni1OH221s2 + OH-1aq2 E°red = +0.49 V

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교과서 질문

A voltaic cell is constructed that uses the following half-cell reactions:

Cu⁺(aq) + e^- → Cu(s)

I₂(s) + 2 e^- → 2 I^-(aq)

The cell is operated at 298 K with [Cu⁺] = 0.25 M and [I^-] = 0.035 M.

(b) Which electrode is the anode of the cell?