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23: Electrochemistry

Last updated

Mar 21, 2025
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- 22.11: Half-Reaction Method in Basic Solution
- 23.1: Direct Redox Reactions

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Topic hierarchy

23.1: Direct Redox Reactions
This page discusses the popularity of gold and silver in jewelry owing to their stability. It explains a redox reaction where zinc displaces copper from copper(II) sulfate, showcasing zinc's higher reactivity. The text highlights spontaneous versus nonspontaneous reactions, noting that copper cannot oxidize zinc, leading to no reaction when copper is introduced to zinc ions.
23.2: Electrochemical Reaction
This page explains that metal sculptures corrode through redox reactions influenced by the elements. It discusses electrochemistry, which converts chemical to electrical energy, seen in batteries. It highlights that direct redox reactions, like those between zinc and copper ions, require separation into oxidation and reduction to perform work in electrochemical cells. These cells feature a solution for reactions, a conductor for electron transfer, and a salt bridge for ion movement.
23.3: Voltaic Cells
This page discusses Luigi Galvani's 18th-century discovery of electrical effects in frog legs, leading to advancements in nerve conduction research. It describes a voltaic cell, an electrochemical device that generates electrical energy via spontaneous redox reactions, including its two half-cells: the anode, which undergoes oxidation (losing zinc), and the cathode, which undergoes reduction (gaining copper).
23.4: Electrical Potential
This page explains how a voltmeter measures electric current indirectly through established galvanometer principles. It discusses electrical potential in voltaic cells, emphasizing that it's measured in volts and depends on half-cell differences. A complete redox reaction, illustrated by a zinc-copper cell, determines this potential, with copper ions being reduced due to their higher reduction potential compared to zinc.
23.5: Standard Hydrogen Electrode
This page emphasizes the need for a universal standard in electrical potential measurements during chemical reactions, highlighting the standard hydrogen electrode (SHE) as the reference point with a defined potential of zero. It explains the SHE's composition and conditions, and illustrates its application in calculating voltages for half-reactions, specifically in zinc and copper reactions, by using standard reduction potentials to determine cell electromotive force (emf).
23.6: Calculating Standard Cell Potentials
This page discusses the corrosion of steel and the use of galvanized nails to prevent rust through zinc coating. It explores electrochemical cells, showing the calculation of cell potential using reduction potentials from a standard table, including an example with tin and silver ions resulting in a spontaneous reaction (+0.94 V).
23.7: Batteries
This page discusses the invention of the first voltaic cell by Alessandro Volta in 1800, which used zinc and silver disks. It outlines modern battery types, including dry cells used in devices like flashlights, and alkaline batteries, which have a longer shelf life. It also describes lead storage batteries, commonly used in vehicles, that consist of six cells and are rechargeable, emphasizing their chemical reactions and potential inefficiencies over time.
23.8: Electrolytic Cells
This page discusses the 1989 claims of achieving cold fusion through electrolysis, which ultimately lacked reproducibility and harmed credibility. Despite this, recent interest in cold fusion has surfaced among researchers. It also explains electrolytic cells, emphasizing their use of external electrical energy to drive nonspontaneous reactions, and highlights the reversed roles of anode and cathode compared to spontaneous reactions.
23.9: Electrolysis of Water
This page discusses the exploration of alternative energy sources, highlighting hydrogen as a potential option due to its clean burning capability. A novel production method, photoelectrolysis, utilizes photovoltaic cells to split water into hydrogen and oxygen, showing promise despite being in early research stages. In contrast, traditional water electrolysis relies on platinum electrodes and an electrolyte like sulfuric acid to generate hydrogen gas.
23.10: Electrolysis of Molten Salts and Electrolysis of Brine
This page discusses the production of sodium hydroxide ( $\ce{NaOH}$ ) via three electrical methods with energy needs of 3300-5000 kWh per metric ton. It details the electrolysis of molten sodium chloride in a Down's cell, which produces sodium metal and chlorine gas, and the electrolysis of brine, which yields chlorine gas and hydrogen while forming hydroxide ions. The brine process is notable for enabling sodium hydroxide extraction through evaporation.
23.11: Electroplating
This page discusses the astrolabe, a brass instrument used for studying planetary motions and astrology, and electroplating, a decorative method that deposits metals onto surfaces via an electrolytic cell. The process uses copper sulfate and a copper anode to ensure consistent copper ion concentration, with the possibility of using other metals like chromium, gold, silver, and platinum in the technique.

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