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topic_9_redox_processes_9.1_to_9.2_19.1.pptx - IB CHEMISTRY...

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Topic 9 Redox processeslevelHigherlevelIB CHEMISTRY
9.1 Oxidation and reductionOBJECTIVES• Oxidation and reduction can be considered in terms of oxygen gain/hydrogen loss,electron transfer or change in oxidation number.• An oxidizing agent is reduced and a reducing agent is oxidized.• Variable oxidation numbers exist for transition metals and for most main-group non-metals.• The activity series ranks metals according to the ease with which they undergo oxidation.• The Winkler Method can be used to measure biochemical oxygen demand (BOD), used asa measure of the degree of pollution in a water sample.• Deduction of the oxidation states of an atom in an ion or a compound.• Deduction of the name of a transition metal compound from a given formula, applyingoxidation numbers represented by Roman numerals.• Identification of the species oxidized and reduced and the oxidizing and reducing agents,in redox reactions.• Deduction of redox reactions using half-equations in acidic or neutral solutions.• Deduction of the feasibility of a redox reaction from the activity series or reaction data.• Solution of a range of redox titration problems.• Application of the Winkler Method to calculate BOD.
1. REDOX CALCULATIONS
GAIN OF OXYGEN2Mg+O2——>2MgOmagnesium has been oxidised as it has gained oxygenREMOVAL (LOSS) OF HYDROGENC2H5OH——>CH3CHO+H2ethanol has been oxidised as it has ‘lost’ hydrogenOxidation
GAIN OF HYDROGENC2H4+H2——>C2H6ethene has been reduced as it has gained hydrogenREMOVAL (LOSS) OF OXYGENCuO+H2——>Cu+ H2Ocopper(II) oxide has been reduced as it has ‘lost’ oxygenHowever as chemistry became more sophisticated, itwas realised that another definition was requiredReduction
...OXIDATIONRemoval (loss) of electrons‘OIL’species will get less negative or more positiveREDUCTIONGain of electrons‘RIG’species will become more negative or less positiveREDOXWhenreduction andoxidation take placeOxidizing agent= substance that causes oxidation to occur.The oxidizing agent is reduced.Reducing agent= substance that causes reduction to occurThe reducing agent is oxidized.Oxidation and reduction are not only defined as changes in O and HOxidation/Reduction in terms of electrons
Which one is the oxidising/reducing agent?Mg+2H+Mg2++H2Cr2O72-+ 14H++ 6Fe2+→ 2Cr3++ 6Fe3++7H2O2MnO4¯+ 5C2O42-+16H+→ 2Mn2++ 10CO2+ 8H2O2S2O32-+I2S4O62-+2I¯OxidisedReducing agentReducedOxidising agentOxidisedReducing agentOxidisedReducing agentOxidisedReducing agentReducedOxidising agentReducedOxidising agentReducedOxidising agent
REDOX agentsOxidising agentsOxygenChlorine and other halogensIron (III) ionHydrogen peroxide (H2O2)Manganate (VII) ion(Permanganate ion MnO4-)Dichromate (VI) ion (Cr2O72-)Reducing agentsHydrogenCarbon and carbonmonoxideMetalsIron (II) ionIodide ionThosulfate ion (S2O32-)
Used to...tell if oxidation or reduction has taken placework out what has been oxidised and/or reduced

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Term
Spring
Professor
carlson

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