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Inorganic reactions (Anorganische Reaktionsmechanismen). Acid-Base reactions Acid + Base salt + H 2 O chlorides, sulfates, nitrates, phosphates,.. REDOX reactions Red uction and ox idation = REDOX rxn. RED OX REACTION. (I) Oxidation
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Inorganic reactions(Anorganische Reaktionsmechanismen) • Acid-Base reactions Acid + Base salt + H2O chlorides, sulfates, nitrates, phosphates,.. • REDOX reactions Reduction and oxidation = REDOX rxn
REDOX REACTION (I) Oxidation Burning process: C+O2 CO2 Why? Oxygen: e-negative element takes up 2 e- from Carbon (C) OXIDATION: Uptake of oxygen Release of electrons(Elektronenabgabe)
REDOX reaction (II) Reduction Release of oxygen (Sauerstoffabgabe) CuO + H2 Cuo + H2O Copperoxide elementary copper reduced to elementary state (zum Elementarzustand reduziert)
REDOXreaction - summary OXIDATION: Uptake of oxygen (O- aufnahme) Release of electrons(e- abgabe) REDUCTION: Release of oxygen Uptake of electrons
Unforced redox reactions[freiwillige Redoxreaktionen] • Batteries (Car battery: Pb/PbO2 system) • Corrosion CORROSION[Korrosion,“Rosten“] Metalls corrode when they come in contact with Oxygen Acids SO2 NOx and other gases
Corrosion of steel:when iron (Eisen) is oxidized • STEEL (Stahl) Oxygen and water let steel corrode Result a mixture of iron salts and iron hydroxides (Eisenhydroxide) FeO, Fe(OH)2, Fe(OH)3, Fe2O3.xH2O Oxidation numbers?
You should know • Oxidation, reduction, definitions • Examples of standard oxidation processes (Oxidation of C, Ca, Al..) • Oxidation numbers • Redox reaction mechanism, examples, redox pair: Experiment with CuO and Fe • Corrosion
Discomfort of dental fillings... • Tooth cavities [Zahnfüllungen] made of amalgams: Sn...tin [Zinn] Ag...silver [Silber] Hg...mercury [Quecksilber] Bite on a piece of aluminum foil, and you know what I mean... = Alloy (Legierung)
Aluminum as reducing agent • Al acts then as a reducing agent, reducing the Ag/Sn/Hg alloy: Sn2+ + 3 Ag Ag3Sn Summary/dental fillings If a piece of Aluminum comes in contact with amalgam, a short electric circuit results [Stromkreis entsteht]
Sources of electric current • Daniell element p. 79 18th century: L. Galvani and A. Volta developed first Galvanic cell (FROG EXPERIMENT)
Daniell element – what we need • Two electrodes: anode, cathode • salt solution • semipermeable membran
Words • source...Quelle • anode...Anode • cathode...Kathode • semipermeable... semipermeable, halbdurchlässig • to conduct...leiten • electron flow...Elektronenfluss • copper sulfate...Kupfersulfat • zinc sulfate... Zinksulfat
e- e- Cu-electrode Zn-electrode CuSO4 solution SO42- SO42- ZnSO4 solution Zn2+ Cu2+ semi- permeable membrane
You should know • Example of an electrochemical source: = Galvanic cell • Developed in 18th century by Galvani and Volta • Anode: Zn, Oxidation • Cathode: Cu, Reduction