Ch.19 - Electrochemistry

McMurry8th EditionChemistryISBN: 9781292336145Not the one you use?Change textbook

McMurry 8th Edition

Ch.19 - Electrochemistry

Problem 19.67

Chapter 19, Problem 19.67

How are standard reduction potentials defined?

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Standard reduction potentials are defined as the voltage associated with a reduction reaction at an electrode when all solutes are at a concentration of 1 M, all gases are at a pressure of 1 atm, and the temperature is 25°C (298 K).

These potentials are measured under standard conditions and are used to predict the direction of electron flow in electrochemical cells.

The standard reduction potential is denoted by E° and is measured in volts (V).

A positive E° value indicates a greater tendency for the species to gain electrons and be reduced, while a negative E° value indicates a lesser tendency.

Standard reduction potentials are typically listed in tables, with the reduction of hydrogen ions to hydrogen gas (2H⁺ + 2e⁻ → H₂) assigned a potential of 0.00 V as a reference point.

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Key Concepts

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

Standard Reduction Potential

Standard reduction potential (E°) is a measure of the tendency of a chemical species to gain electrons and be reduced. It is defined under standard conditions (1 M concentration, 1 atm pressure, and 25°C) and is measured in volts. A higher E° value indicates a greater likelihood of reduction occurring, making it a crucial parameter in electrochemistry.

Electrochemical Cells

Electrochemical cells are devices that convert chemical energy into electrical energy through redox reactions. They consist of two electrodes: an anode (where oxidation occurs) and a cathode (where reduction occurs). The standard reduction potentials of the half-reactions at these electrodes determine the overall cell potential and the direction of electron flow.

Nernst Equation

The Nernst equation relates the standard reduction potential of a half-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, providing insight into how changes in concentration affect the driving force of the reaction.

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Related Practice

Textbook Question

The silver oxide–zinc battery used in watches delivers a voltage of 1.60 V. Calculate the free-energy change (in kilo-joules) for the cell reaction

Textbook Question

Calculate the standard cell potential and the standard free-energy change (in kilojoules) for the reaction below. (See Appendix D for standard reduction potentials.) <QUESTION REFERENCES APPENDIX D>

Textbook Question

Consider a Daniell cell with 1.0 M ion concentrations:

Does the cell voltage increase, decrease, or remain the same when each of the following changes is made? Explain. (a) Write a balanced equation for each cell reaction.

Textbook Question

Sketch a cell with inert electrodes suitable for electrolysis of aqueous CuBr2. (b) Indicate the direction of electron and ion flow.

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Textbook Question

Porous pellets of TiO₂ can be reduced to titanium metal at the cathode of an electrochemical cell containing molten CaCl₂ as the electrolyte. When the TiO₂ is reduced, the O^2-ions dis-solve in the CaCl₂ and are subsequently oxidized to O₂ gas at the anode. This approach may be the basis for a less expensive process than the one currently used for producing titanium.

(a) Label the anode and cathode, and indicate the signs of the electrodes.