Ch9. Redox
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Definitions
Anode: Where oxidation takes place. In electrolysis, it is the + electrode and anions are attracted here.
Cathode: Where reduction takes place. In electrolysis, it is the – electrode and cations are attracted here.
Electrolysis: Passage of electric current through an electrolyte. Amount of discharge is affected by: 1) current; 2) charge on ion, 3) duration of electrolysis.
Electrolyte: A substance which does not conduct electricity when solid, but does when molten or in aqueous solution and is chemically decomposed in the process.
Electrolytic cell: Used to make non-spontaneous redox reactions occur by providing energy in the form of electricity from an external source.
Electroplating: A process of coating one metal with a thin layer of another metal, by electrolysis.
Half cell: A metal in contact with an aqueous solution of its own ions.
Oxidation: The loss of electrons
Oxidizing agent: A substance that readily oxidizes other substances. Oxidizing agents are thus reduced.
Reactivity: A measure of the readiness of a substance to gain or lose electrons. The stronger the reducing agent or oxidizing agent, the more reactive it is.
Redox reaction: A reaction in which there is a transfer of electrons, i.e. reduction and oxidation occurring simultaneously.
Reducing agent: A substance that readily reduces other substances. Reducing agents are thus oxidized.
Reduction: The gain of electrons
Salt bridge: Allows the free movement of ions in a voltaic cell. Paper dipped in a saturated solution of KNO3 is an example of a salt bridge.
Shorthand notation: For a voltaic cell. Example: Cu(s)/Cu2+(aq) || H+(aq) / H2(g)
Standard conditions: 298 K, 1 atm, 1.0 M.
Standard electrode potential: The electrode potential of one half-cell compared against another half-cell, by convention, the hydrogen half-cell, which is arbitrarily given a value of 0 V.
Standard cell potential: Difference between the two standard electrode potentials of the two half cells.
Standard hydrogen electrode: Arbitrarily assigned a potential of zero. Electrode consists of an inert metal such as platinum dipped into a 1 M solution of HCl, where hydrogen gas at 1 atm flows in.
Voltaic cell: Two different half-cells connected together to enable to electron transferred during the redox reaction to produce energy in the form of electricity. The electrons are produced at the half-cell that is most easily oxidized.
•Electrolytic vs. Voltaic cell [.pdf]
•Redox key points for HL (v.4) [.pdf]
•Mindmap of redox material for HL [.jpg]
• Products of electrolysis of aqueous solutions [link]
