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Published byBrice Nelson Modified over 8 years ago
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Nernst Equation G = -nF cell G o = -nF o cell G = cell = o cell - RT nF ln Q standard non-standard GoGo + RT ln Q
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Nernst Equation Cu (s) cell = o cell - RT ln Q nF o cell = 0.80 - 0.34 = 0.46 V Cu 2+ + 2e - CuAg + + e - Ag(s) o red - o ox = o = 0.34 V o = 0.80 V 2( ) b) reductionoxidation anode cathode Cu 2+ (aq) (1M ) 4M4M Cu (s) Cu 2+ + 2e - a) oxidation Ag + (aq) (1M) Ag (s)
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Nernst Equation Cu (s) Cu 2+ (aq) (4M) Ag + (aq) (1M) Ag (s) cell = o cell - RT ln Q nF Cu (s) Cu 2+ + 2e - 2Ag + + 2e - 2Ag (s) Q = = [Cu 2+ ] [Ag + ] = 4 1212 [products] m initial [reactants] n initial anode cathode 2
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Nernst Equation Cu (s) Cu 2+ (aq) (4M) Ag + (aq) (1M) Ag (s) cell = o cell - RT ln Q nF Cu(s) Cu 2+ + 2e - 2Ag + + 2e - 2Ag cell = 0.46V 2 = 0.44 V -(298) ln 4 (96,500) (8.314) anodecathode
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Non-standard conditions G =G = = -85 kJ -(2 mol e - )(96,500 C/mol e - ) (0.44V) Cu (s) Cu 2+ (aq) (4M) Ag + (aq) (1M) Ag (s) Cu(s) Cu 2+ + 2e - 2Ag + + 2e - 2Ag G o = = -89 kJ -(2 mol e - )(96,500 C/mol e - ) (0.46V) G = -nF
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V Ni (s) Ag (s) 1 x 10 -3 M NiCl 2 1.0 M HCl AgCl (s) ξ = 0.54 VK sp AgCl = 0.54 =1.03 Ag + + e - → Ag (s) ξ o = 0.80 V Ni 2+ + 2e - → Ni (s) ξ o = -0.23 V -RT/nFln Q ln Q = 38.17 Q = 3.78 x 10 16 [Ag + ] 2 = [Ni 2+ ] [Ag + ] = 1.62 x 10 -10 [Ag + ][Cl - ] [AgCl] 1.62 x 10 -10 K sp =
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Concentration cell Cu (s) Cu(s)Cu 2+ oxidationreduction cell = o cell = o red - o ox = 0.34 - 0.34= 0 o cell - RT nF ln Q Cu 2+ (aq) (0.5M) Cu 2+ (aq) (2M) Cu (s) + 2e - Cu(s) Cu 2+ + 2e - 0 V
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Concentration Cells Cu (s) Cu 2+ (aq) (0.5M) Cu 2+ (aq) (2M) Cu (s) Cu(s) Cu 2+ + 2e - Cu 2+ + 2e - Cu(s) = [products] m initial = o cell = [Cu 2+ ] [reactants] n initial anode cathode = 0.5= 0.25 2 Q cell = -RT 2F ln.25 =.02 V oxidationreduction [Cu 2+ ] cathode -RT nF ln Q0
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Concentration Cells P 680 QAQA + - h Mn 2H 2 O4H + pH = 3.0 pH = 7.0 cell = o cell - RT ln Q nF cell = o cell - 0.059 log Q n ADP + P i ATP G > 0 Q = 10 -7 / 10 -3 cell = 0.24 V G < 0 + O 2 + 4e - +
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2H + + 2e - H 2 o = 0.00 V MnO 4 - + 8H + Mn 2+ + 4 H 2 O +5e - o = 1.51 V o cell = G o = -nF o 2MnO 4 - + 6H + + 5H 2 2Mn 2+ + 8 H 2 O Go =Go = o red - o ox = 1.51 - 0 = 1.51 V = - (10)(96,500)(1.51) = -1457 kJ -RT ln K= -1457 kJ -RT K = e 588
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Balancing Redox Reactions MnO 4 - Mn 2+ manganese is balanced MnO 4 - Mn 2+ + balance oxygen using H 2 O 4H2O4H2O balance hydrogen using H + MnO 4 - + Mn 2+ + 4 H 2 O 8H + balance charge using e - MnO 4 - + 8H + Mn 2+ + 4 H 2 O +5e -
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Oxidation States MnO 4 - + 8H + Mn 2+ + 4 H 2 O +5e - MnO 4 - Oxidation state of oxygen = Oxidation state of hydrogen = 4 x (-2)+ 1(Mn)= -1 Mn = 7+ Mn 2+ Mn = 2+ Mn 7+ + 5 e - Mn 2+ 0 in O 2 2- in compounds 1+ in compounds 0 in H 2
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2H + + 2e - H 2 o = 0.00 V MnO 4 - + 8H + Mn 2+ + 4 H 2 O +5e - o = 1.51 V reduction reaction MnO 4 - +8H + +5e - Mn 2+ +4 H 2 O oxidation reaction H 2 2H + +2e - anode Pt (s) 2MnO 4 - + 16H + +10e - + 5H 2 2Mn 2+ + 8 H 2 O + 10H + + 10e - 2MnO 4 - + 6H + + 5H 2 2Mn 2+ + 8 H 2 O cathode H 2 (g) (1atm) H + ( aq) (1M) Pt (s) Mn 2+ (aq) (1M)MnO 4 - (aq)( 1M), 6,H + (1M) ( )5( )2
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