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Ch.20 - Electrochemistry
Tro - Chemistry: A Molecular Approach 5th Edition
Tro5th EditionChemistry: A Molecular ApproachISBN: 9780134874371Non è quello che usi tu?Cambia libro di testo
Capitolo 20, Problema 78b

A voltaic cell consists of a Pb/Pb2+ half-cell and a Cu/Cu2+ half-cell at 25°C. The initial concentrations of Pb2+ and Cu2+ are 0.0500 M and 1.50 M, respectively. b. What is the cell potential when the concentration of Cu2+ has fallen to 0.200 M?

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Identify the half-reactions for the Pb and Cu electrodes. For the Pb electrode, the half-reaction is Pb^2+ + 2e^- \(\rightarrow\) Pb(s). For the Cu electrode, the half-reaction is Cu^2+ + 2e^- \(\rightarrow\) Cu(s).
Write the overall cell reaction by combining the two half-reactions. The electrons should cancel out, resulting in: Pb(s) + Cu^2+ \(\rightarrow\) Pb^2+ + Cu(s).
Use the Nernst equation to calculate the cell potential. The Nernst equation is E = E^0 - \(\frac{RT}{nF}\) \(\ln\) Q, where E^0 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 the Faraday constant, and Q is the reaction quotient.
Calculate the standard cell potential, E^0, using the standard reduction potentials of the half-reactions. E^0 = E^0_{Cu} - E^0_{Pb}, where E^0_{Cu} and E^0_{Pb} are the standard reduction potentials for copper and lead, respectively.
Determine the reaction quotient, Q, using the initial and final concentrations given. Q = \(\frac{[Pb^2+]}{[Cu^2+]}\), where [Pb^2+] and [Cu^2+] are the concentrations of Pb^2+ and Cu^2+ at the specified point in the reaction.

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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, creating a flow of electrons that generates an electric current. Understanding the roles of the half-cells and the overall cell reaction is crucial for analyzing cell potential.
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Electrochemical Cells

Nernst Equation

The Nernst equation relates the cell potential to the concentrations of the reactants and products in a redox reaction. It allows for the calculation of the cell potential under non-standard conditions, taking into account temperature and concentration changes. This equation is essential for determining how changes in ion concentration affect the overall voltage of the cell.
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The Nernst Equation

Standard Electrode Potentials

Standard electrode potentials are measured voltages for half-reactions under standard conditions (1 M concentration, 1 atm pressure, and 25°C). These values are used to predict the direction of electron flow and the feasibility of redox reactions. Knowing the standard potentials for the Pb and Cu half-reactions is necessary to calculate the initial cell potential and apply the Nernst equation for concentration changes.
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Standard Cell Potential
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A voltaic cell consists of a Zn/Zn2+ half-cell and a Ni/Ni2+ half-cell at 25 °C. The initial concentrations of Ni2+ and Zn2+ are 1.50 M and 0.100 M, respectively. c. What are the concentrations of Ni2+ and Zn2+ when the cell potential falls to 0.45 V?

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Domanda del libro di testo

A voltaic cell consists of a Zn/Zn2+ half-cell and a Ni/Ni2+ half-cell at 25 °C. The initial concentrations of Ni2+ and Zn2+ are 1.50 M and 0.100 M, respectively. b. What is the cell potential when the concentration of Ni2+ has fallen to 0.500 M?

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A voltaic cell consists of a Pb/Pb2+ half-cell and a Cu/Cu2+ half-cell at 25°C. The initial concentrations of Pb2+ and Cu2+ are 0.0500 M and 1.50 M, respectively. a. What is the initial cell potential?

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A voltaic cell consists of a Pb/Pb2+ half-cell and a Cu/Cu2+ half-cell at 25°C. The initial concentrations of Pb2+ and Cu2+ are 0.0500 M and 1.50 M, respectively. c. What are the concentrations of Pb2+ and Cu2+ when the cell potential falls to 0.35 V?

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Consider the concentration cell: b. Indicate the direction of electron flow.

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