Ch.20 - Electrochemistry

Brown - Chemistry: The Central Science 15th Edition

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Brown 15th Edition

Ch.20 - Electrochemistry

Problem 72a

Chapter 20, Problem 72a

A voltaic cell utilizes the following reaction: 2 Fe3+1aq2 + H21g2 ¡ 2 Fe2+1aq2 + 2 H+1aq2 (a) What is the emf of this cell under standard conditions?

Verified step by step guidance

Step 1: Identify the half-reactions involved in the overall cell reaction.

Step 2: Write the reduction half-reaction and the oxidation half-reaction separately.

Step 3: Use the standard reduction potentials from a table to find the potential for each half-reaction.

Step 4: Calculate the standard cell potential (emf) by subtracting the oxidation potential from the reduction potential.

Step 5: Ensure the units are consistent and the final expression is in volts (V).

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Key Concepts

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

Electrochemical Cells

Electrochemical cells are devices that convert chemical energy into electrical energy through redox reactions. A voltaic cell, specifically, generates electricity spontaneously from a chemical reaction, involving oxidation and reduction processes occurring in separate half-cells. Understanding the structure and function of these cells is essential for analyzing their emf (electromotive force) and overall efficiency.

Standard Electrode Potentials

Standard electrode potentials are measured voltages that indicate the tendency of a species to be reduced, measured under standard conditions (1 M concentration, 1 atm pressure, and 25°C). Each half-reaction in a voltaic cell has a specific standard electrode potential, which can be used to calculate the overall cell potential (emf) by subtracting the anode potential from the cathode potential. This concept is crucial for determining the emf of the cell in the given reaction.

Nernst Equation

The Nernst equation relates the emf of an electrochemical cell to the concentrations of the reactants and products involved in the redox reaction. It allows for the calculation of the cell potential under non-standard conditions, taking into account temperature and concentration variations. Understanding this equation is important for predicting how the emf changes as the reaction progresses or as conditions vary.

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The Nernst Equation

Related Practice

Textbook Question

During a period of discharge of a lead–acid battery, 402 g of Pb from the anode is converted into PbSO₄(s). (a) What mass of PbO₂(s) is reduced at the cathode during this same period?

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Textbook Question

A voltaic cell utilizes the following reaction: 4 Fe2+1aq2 + O21g2 + 4 H+1aq2 ¡ 4 Fe3+1aq2 + 2 H2O1l2 (b) What is the emf of this cell when 3Fe2+4 = 1.3 M, 3Fe3+4= 0.010 M, PO2 = 0.50 atm, and the pH of the solution in the cathode half-cell is 3.50?

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Textbook Question

A voltaic cell is constructed that is based on the following reaction: Sn²⁺(aq) + Pb(s) → Sn(s) + Pb²⁺(aq) (a) If the concentration of Sn²⁺ in the cathode half-cell is 1.00 M and the cell generates an emf of +0.22 V, what is the concentration of Pb²⁺ in the anode half-cell?

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Textbook Question

A voltaic cell utilizes the following reaction: Al1s2 + 3 Ag+1aq2 ¡ Al3+1aq2 + 3 Ag1s2 What is the effect on the cell emf of each of the following changes? (a) Water is added to the anode half-cell, diluting the solution.

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Textbook Question

A voltaic cell utilizes the following reaction: (b) What is the emf for this cell when 3Fe3+4 = 3.50 M, PH2= 0.95 atm, 3Fe2+4 = 0.0010 M, and the pH in both half-cells is 4.00?

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