Red Reactio - the basics Ch. 4 & 6 Itroductio to lectrochemistry & Red Titratios Reduced Oxidizig get Reducig get Oxidized <> Red reactios: ivolve trasfer of electros from oe species to aother. Oxidizig aget (idat: takes electros Reducig aget (uctat: gives electros Stadard lectrode Potetials Stadard uctio potetial ( 0 is the voltage associated with a uctio reactio at a electrode whe all solutes are ad all gases are at atm. Stadard hydroge electrode (S... Reductio Reactio ( e - 0 0 ( atm Stadard Reductio (alf-ll Potetials The S... is the cathode. It cosists of a Pt electrode i a tube placed i solutio. is bubbled through the tube. For the S..., we assig (aq, e - (g, atm of zero. The potetial of a cell ca be calculated from stadard uctio potetials: ( cathode ( aode cell Stadard Reductio (alf-ll Potetials Cosider Z(s Z (aq e -. We measure cell relative to the S... (cathode: cell (cathode - (aode 0.76 0 - (aode. Therefore, (aode -0.76. Stadard uctio potetials must be writte as uctio reactios: Z (aq e - Z(s, -0.76. Stadard Potetials We use hydroge (S... (aq e /( g 0.000 We ca measure º for other half-reactios, relative to the hydroge reactio, e.g. for silver: g (aq e g(s 0.799 Stadard uctio potetials are listed i p. i your book. º for the reactio is for the reactio at 5 º C
Nerst quatio for a alf-reactio The Nerst quatio relates the potetial of the half reactio to equilibrium coditios For the half-reactio: - a e b l F b [ [ a - a b e cc dd l F c d [ C [ D [ a [ b F l Q # of moles of electros Nerst quatio for a alf-reactio Nerst quatio for a Complete Reactio t 98K (5 o C 0.0596 logq <> xample (Nerst Write the Nerst equatio for the uctio of phosphoric acid to solid white phosphorous: - PO4 5 5e /4P4 ( s 4 O -.40 0.0596 0.40 log 5 [ PO [ 5 4 Note that multiplyig the reactio by ay factor does ot affect º or the calculated : - PO4 e /P4 ( s 8O 0.0596 0.40 log [ PO [ 4 -.40 xample (Net Reactio Fid the voltage for the g-cd cell ad state if the reactio is spotaeous if the right cell cotaied 0.50 gno (aq ad if the left cotaied 0.0 Cd(NO (aq g e g( s 0.799 Cd e Cd( s 0.40 4 5 g e g( s Cd e Cd( s 0.0596 0.799 log 0.78 [ 0.50 0.0596 0.40 log 0.46 [ 0.0 0.78 ( 0.46.4 Cd( s g Cd g( s
Determiatio of the quivalece Poit Red Titratio Curve t equivalece poit, cell0: 0.059 [ log [ <> ad o at the equivalece poit 0.059 [ log [ o alid for simple Red expressios XPL: Derive the titratio curve for 50.00 ml of 0.0500 with 0.00 4 i a medium that is.0 i ClO 4. Potetial of saturated calomel electrode is 0.4. XPL: Derive the titratio curve for 50.00 ml of 0.0500 with 0.00 4 i a medium that is.0 i ClO 4. Potetial of saturated calomel electrode is Titratio reactio: 4 <> e - <> 4 e - <> o 0.767 o.70 t 0.00 ml of 4 added, iitial poit o 4 preset; miimal, ukow [ ; thus, isufficiet iformatio to calculate 0.059 [ log 0.4 [ 0.059.54 0.767 log.08 0.4 0.5 XPL: Derive the titratio curve for 50.00 ml of 0.0500 with 0.00 4 i a medium that is.0 i ClO 4.Potetial of saturated calomel electrode is 4 <> t 5.00 ml of 4 added, > uffer regio [ (5.00mL(0.00.08 (50.00 5.00 ml XPL: Derive the titratio curve for 50.00 ml of 0.0500 with 0.00 4 i a medium that is.0 i ClO 4. Potetial of saturated calomel electrode is 4 <> t 5.00 ml of 4 added, > uffer regio [.08 [ (50.00mL(0.0500 (5.00mL(0.00.54 (50.00 5.00 ml XPL: Derive the titratio curve for 50.00 ml of 0.0500 with 0.00 4 i a medium that is.0 i ClO 4. Potetial of saturated calomel electrode is 4 <> t 5.00 ml of 4 added, > uffer regio alf-reactios: e - <> o 0.767 [.08 [.58 0.059 [ log [ 0.4 0.059.54 0.767 log.08 0.4 0.5
XPL: Derive the titratio curve for 50.00 ml of 0.0500 with 0.00 4 i a medium that is.0 i ClO 4. Potetial of saturated calomel electrode is 4 <> t 5.00 ml of 4 added,, quivalece poit alf-reactios: e - <> o 0.767 4 e - <> o.70 0.4 0.767.70 0.4. 0.4 0.99 XPL: Derive the titratio curve for 50.00 ml of 0.0500 with 0.00 4 i a medium that is.0 i ClO 4. Potetial of saturated calomel electrode is 4 <> t 6.00 ml of 4 added, <, fter equivalece poit [ (50.00mL(0.0500.9 (50.00 6.00 ml XPL: Derive the titratio curve for 50.00 ml of 0.0500 with 0.00 4 i a medium that is.0 i ClO 4. Potetial of saturated calomel electrode is 4 <> t 6.00 ml of 4 added, <, fter equivalece poit [ 4 [.9 (6.00mL(0.00 (50.00mL(0.0500. (50.00 6.00 ml XPL: Derive the titratio curve for 50.00 ml of 0.0500 with 0.00 4 i a medium that is.0 i ClO 4. Potetial of saturated calomel electrode is 4 <> t 6.00 ml of 4 added, > fter equivalece poit alf-reactios: e - <> o 0.767 4 e - <> o.70 4 [.9 [. 0.059 [ log [ 4 0.059.9.70 log. 0.4 0.4 0.6 Theoretical curve for titratio of 0.0 ml of 0.50 0 with 0.0 4 i ClO 4. (p.0-0.059 [ log 0.4 [ 0.059 0.767 log 0.4 0.56 4
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