Potenciais de redução metais

7/27/2019 Potenciais de reduo metais

1/6

PROC~ PRINCIPL~ IN MINERALS AND MATERIALS PRODUCTION

D.2.2 STANDARD REDUCTION POTENTIALSI:4BLE D.2.2 Standard electrode potentials and redox equilibria in aqueous solutions at 25C

(Aylward and Findlay) (Copyright Jacaranda Wiley)The standard electrode potential, Eo, of the half cell system,

Mn+ + ne +:t M(I)'is the potential of the right-hand electrode less that of the left-hand electrode in thecell

Pt, H2IH+ IIMn+IMwhen the activities of all ions in the cell are unity, when gases are at I atm (101.325kPa) pressure and solids are in their most stable form at 25C.

The overall cell reaction may be represented asMn+ + ~ H2(1) ~ M(I) + nH +.

If the electrode potential is positive, the above reaction is the spontaneous reactionin the direction left to right. If the electrode potential is negative, the spontaneousreaction is in the opposite direction.The logarithm of the constant for the redox equilibrium, K, for the overall cellreaction as written above is shown in the last column of the Table. If the equilibriumconstant, KH, for the hydrogen half-cell reaction is taken as unity, that is

aH+ .a.-It' --~ ~ 1~~H -t -&,PH2K may be considered as a measure of the relative electron activity of the half-cellreaction in which the electron may be regarded as the ligand, that is

nKMn+/M = Mn+ .-

E0/V Jog KeactionlementAt3+ +3e -~ At(s) -}.66 -84.5luminium

Antimony tSb2O5(s,+2H++2e- .,= tSb2O3(s)+H2OtSb2O3(s)+3H+ +3e -.,= Sb(s,+iH2OSbO++2H++3e- .,= Sb(s)+H2OSb(l) + 3H + + 3e -.,= SbH 3(1)

0-69 22.70-15 7.70.21 10-8

-0-51 -25.9

H3AsO4+2H++2e- ~ H3AsO3+HlOH3AsO3+JH+ .tJe -~ As(I)+3HlO

As(I)+JH++Je- ~ AsH3\,)0-56 18-90-25 12-6

-0-60 -30.8Arsenic

Barium Ba2++2e- ~ Bals) -2-90 -98-2

/i60


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D SOURC~ OF DATA

TABLE D.2.2 cont'dSTANDARD ELECTRODE POTENTIALS (continued}

Element Reaction E0/V log K

Beryllium Be2++2e- ~ Be(s) -1-85Bismuth 0.32

0.1610.88.1

BiO++2H++2e- ~ Bi(5)+H2OBiOCI(5)+2H++3e- ~ Bi(,)+H2O+CI-

Boron H3BO3+3H++3e- ~ B+3H20 -0.87-44.0Bromine BrOJ -+6H+ +5e -~ tBr2(1)+3H2O

HOBr+H++e- ~ tBr2(1)+H2OtBr2(1)+e- ~ Br -tBr2(aq)+e- ~ Br-

1.521.591.071.09

128.327.018.118.4

Cadmium Cd2++2e- ~ Cd(s) -0-40 -13-6Caesium Cs++e- ~ Cs(.) -2-92Calcium Ca2++2e- ~ Ca(.) -'2.87Carbon CO2(8)+2H++2e- ~ CO(I)+H2O

CO2(8)+2H++2e- ~ HCOOHCO2(8)+2H++2e- ~ H2C2O4

-0.12 -3.5-0.20 -6.71-0.49 -15.9

Cerium Ce4++e- ~ Ce3+ (1 M HCIO4)(I M HNO3)(1 M H2SO4)(1 M HCI)

1-74 29.51.61 27-21.44 24.41-28 21-6

-2-48 -125-9e3++3e- ~ Ce(.)Chlorine CIO4- +2H++2e -~ CIO3 -+H2O

CIO3- +2H+ +e -~ CIO2(1)+ H2OCIO3- +3H++2e -~ HCIO2+H2OCIO3- +6H++5e- ~ tCI2(1)+3H2O

HOCI+H++e- ~ tCI2(1)+H2OtCI2(1)+e- ~ CI-tCI2(.q)+e- ~ CI-

1.191-151.211-471-631-361.40

40.219.541.0

124.227.523.023.6

Chromium iCr2072-+7H++3e- ~ Cr3++tH2OHCrO4-+7H++3e- ~ Cr3+-t4H20

Cr3++e- ~ Cr2+Cr3++3e- ~ Cr(S)

Cr2+2e- ~ Cr(S)

1-33 67-61-20 60-6

-0-41 -6-9-0-74 -37-7-0-91 -30-9

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PROCESS PRINCIPL~ IN MINERALS AND MATERIALS PRODUCTION

1'ABLE D.2.2 cont'd

STANDARD ELECTRODE POTENTIALS (continued)

Element Reaction E0/V tog KCobalt 1.81 30'6

0.1 1.8-0.28 -9.4-0.43 -14.5

Copper 0.16 2.70.05 0.90-54 9-10-64 10.80-86 14.50-34 11.4

-0-04 -1-60- 52 8.8-0.14 -2.40-12 2-02-87 48.4luorine

Gallium

Co3++e- ~ CO2+Co(NH3)63++e- ~ Co(NH3)62+

Co2++2e- ~ CO(I)Co(NH3)62++2e- ~ Co(I)+6NH3

Cu2++e- ~ CU+Cu(NH3)42++e- ~ Cu(NH3)2++2NH3

Cu2++CI-+e- ~ CuCI(I)Cu2++Br-+e- ~ CuBr(l)

Cu2++I-+e- ~ Cul(l)Cu2++2e- ~ CU(I)

Cu(NH3)42++2e- ~ Cu(I)+4NH3Cu++e- ~ CUll)Cu(NH3)2+ +e- ~ Cu(I)+2NH3

CuCI+e- ~ Cu(I)+CI-!F2+e- ~ F-

Ga3++2e- ~ Ga+Ga3++3e- ~ Gall)

-0.4 -13.5-0.56 -28-4

Germanium Ge2+ +2e- ~ Ge(l)Au3++2e- ~ Au+

Au+ +e- ~ Au(l)

0.23 7.8Gold 1.41

1.6847.728.4

Hydrogen H++e- ~ iH2(1) o 0(by definition)

1.77 59.82O2+2H++2e- ~ 2H2OIn8+ +2e -~ In+In + +e- ~ In(s)Indium -0.40 -13.7-0.23 -3.8

Iodine 1.20 101.01.45 24.30.54 9.10.62 10.50.54 18.1

Iron 0.77 13.00.36 6.11.18 20.0

-0.06 -2.0-0.44 -14.9

103- +6H++5e- ~ !12(s)+3H2OHOI+H++e- ~ !12(s)+H2O

!12(s)+e- ~ I-!12(aq)+e- ~ 1-13- +2e ~ 31-Fe3++e ~ Fe2+

Fe(CN)63- +e- ~ Fe(CN)64-Fe(0-phen)33++e- ~ Fe(0-phen)J2+.

Fe3++3e- ~ Fe(s)Fe2 + + 2e- ~ Fe(s).o-phen = o-phenanthroline.

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D SOURC~ OF DATA

TABLE D.2.2 cont'dSTANDARD ELECTRODE POTENTIALS (continued)

Reaction EO/V logKlement-2.52 -127.9anthanum La3++3e- ~ La(s)

Pb4++2e- ~ Pb2+(I.1 M HCIO4)PbO2(.)+4H++2e- ~ Pb2++2H20

PbO2(.)+4H+ --!-SO42- +2e- ~ PbSO4(s)+2H2OPb2++2e- ~ Pb(s)

PbO(.)+2H++2e- ~ Pb(s)+H2OPbSO4(s)+2e- ~ Pb(s)+SO42-

Lead 1-66 56-01-46 49-21-69 57-0

-0-13 -4-30-25 8-4

-0-36 -12-0Lithium Li+e- ~ Li(s) -3.05 -51.5

Mg2++2e- .= Mg(.) -2-36 -79.8Magnesium0.58 9.71.70 85.81.51 127;41.23 41.61,49 25.2

-1.18 -40.0

Manganese MnO4- +e- ~ MnO42-MnO4- +4H+ +3e- ~ MnO2(S)+2H2OMnO4- +8H++5e- ~ Mn2++4H20MnO2(s)+4H++2e- ~ Mn2++2H20

Mn3++e- ~ Mn2+(7.5 M H2SO4)Mn2++2e- ~ Mn(s)

Mercury 0.910-850.790.27*0.14

-0-04

15.28.13'4'2.

-0.-0.27 -9-)-0.52 -17-7Nickel

Hg2++e- ~ !Hg22+Hg2++2e- ~ Hg(,J

!Hg22++e- ~ Hg11J!Hg2CI21.)+e- ~ H~I)+Cl-!Hg2Br21.)+e- ~ H~I)+Br-

!Hg2121.)+e- ~ HgI1)+I-Ni2++2e- ~ Nil.)

Ni(NHJ)62++2e- ~ Nil.)+6NHJ0.80 13.60.94 31.60.96 48.50.88 119.21.00 17.01.59 53.81.77 59.7

-3.1 -52.3-1.87 -31.7-0.23 -15.4

Nitrogen NO3-+2H++e- ~ -lN2O4(1)+H2ONO3- +3H++2e- ~ HNO2+H2ONO3-+4H++3e- ~ NO(I)+2H2O

NO3-+10H++8e- ~ NH4++3H2OHNO2+H++e- ~ NO(I)+H2O2NO+2H++2e- ~ N2O(I)+H2ON2O(I)+2H++2e ~ N2(1'+H2O

iN2(1)+H++e- ~ HN3-lN2(1)+H2O+2H++e- ~ NH3OH+

N2(1)+5H...+4e- ~ N2Hs+.The potential of the "saturated calomel" reference electrode

KCI (saturated) I Hg2CI2 (s), Hgrelative to the standard hydrogen electrode is 0.2444 Vat 25C.

663

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PROCESS PRINCIPL~ IN MINERALS AND MATERIALS PRODUCTION

I:4.BLE D.2.2 cont'd

STANDARD ELECTRODE POTENTIALS (continued)Reaction E0/V logKlement

1.351.281,230.680'402.070'99

-0.28-0.50-0-51

0-060-681-20.73

-2.93-2-92-2-92-2'08

1-150.74

-0-37-0'92

Oxygen

PalladiumPhosphorus

Platinum

PotassiumRadiumRnbidiumScandiumSelenium

Silicon -0.86.0-101-762-001-400.80

-0-14-0-38

0.371-17

-0.040-220-07

-0-15

Silver

NH3OH++2H++2e- ~ NH4++H1OiN1H5++iH++e- ~ NH4+

!02(1)+2H+ +2e- ~ H2O02(1)+2H++2e- ~ H1O2

!02(1)+H2O+2e- ~ 20H-03(1)+2H++2e- ~ 02(1)+H2O

Pd2++2e- ~ Pd(.)H3PO4+2H++2e- ~ H3PO3+H20H3PO3+2H++2e- ~ H3PO2+H1O

H3PO2+H++e- ~ P(.)+2H20P(.)+3H++3e- ~ PH3(1)

PtC162- ~ PtC142- +2CI-Pt1++2e- ~ Pt(.)

PtC141- +2e- ~ Pt(.)+4CI-K++e- ~ K(.)

Ra2++2e- ~ Ra(,)Rb+ +e- ~ Rb(.,

SC1+ +2e- ~ Sc(.)SeO42-+4H++2e- ~ H2SeO3+H1OH2SeO3+4H++4e- ~ Se(.)+3H2O

Se(.)+2H++2e- ~ H2Se(l)Se(.)+2e- ~ Se2-

SiO2(.)+4H++4e- ~ Si(.)+2H2OSj(.)+4H+ +4e- ~ SjH4(1)

!Ag2O3(.)+3H+ +2e- ~ Ag+ +~H2OAg2+ +e- ~ Ag+(4 M HCIO4)

AgO(.)+H++e- ~ !Ag2O+!H2OAg+ +e- ~ A~.)

AgCN(.)+e- ~ A~.)+CN-Ag(CN)2- +e- ~ Ag(.)+2CN-

Ag(NH3)2++e- ~ A~.)+2NH3!Ag2O(.)+H++e- ~ A~.)+!H2O!Ag2S(.)+H+ +e- ~ A~.)+ tH2S(I)

AgCI(.)+e- ~ Ag(.)+CI-AgBr(.)+e- ~ A~.)+Br-

AgI(.)+e- ~ Ag(.)+I-

(564

45-621.641-623.113.670.233-4

-9.3-16.9

-8.63.223.0

40.024.5

-49.5-98.6-49.4-105.3

38.950.0

-12-5-31.2-57.9

6.959.433.823.713.51

-2.4-6.3

6.319.8

-1.23.81.2

-2.6


6/6

D SOURC~ OF DATA

TABLE D.2.2 cont'dSTANOARO ELECTRODE POTENTIALS (continued)

E0/V logKeactionlement-2-71 -45-9Na + +e- ~ Na(s)Sodium-2.89 -97.6r2++2e- ~ Sr(S)trontium

2.01 33.90-17 5-80.40 27.00.45 30.40.08 1-4

-0.48 -16-10.17 5-8

Sulphur tSlO8l-+e- ~ SO4l-SO4l-+4H++2e- ~ HlSO3+HlOHlSO3+2H+ +4e- ~ SlO3l- +3HlOHlSO3+4H++4e- ~ S(I)+3HlO

tS406l- +2e- ~ SlO3l-S(I)+2e- ~ Sl-

S(I)+2H++2e- ~ HlS(I)1-02 34-60-53 35-8

-0-72 -25-0-1-14 -38-6

Tellurium

1-26 42-6-0-34 -5-7-0-56 -9-4-0-66 -II-I-0-77 -13-0

Thallium

0.15 5.2-0.14 -4.6

-0.06 -0.9-0.37 -6.2-).63 -55

Te(OH)6(s,+2H++2e- ~ TeO2(SI+4H2OTeO2(s)+4H++4e- ~ Te(SI+2H2OTe(s)+2H++2e- ~ H2Te(11

Te(s)+2e- ~ Te2-T13+ +2e- ~ TI+

TI++e- ~ TI(slTICI(sl+e- ~ TI(s)+CI-TIBr(sl+e- ~ TI(s)+Br-

TII(sl+e- ~ TI(sl+I-

Sn4++2e- ~ Sn2+Sn2+ +2e- ~ Sn(S)TiOH3++H++e- ~ Ti3++H20

Ti3++e- ~ Ti2+Ti2++2e- ~ Ti(sl

Titanium

VO22++e- ~ VO2+VO2++4H++e- ~ V4++2H20

V4++e- ~ V3+V3++3e- ~ V(S)

0.05 0.90.33 5.6

-0.61 -10.3-1.80 -91

Uranium

1-00 16.90-34 5-7

-0,26 -4-3-1-18 -40-!

VO2++2H++e- ~ VO2++H20VO2++2H++e- ~ V3++H20

V3++e- ~ V2+V2++2e- ~ V(5)

Vanadium

-0.76 -25-8-1.04 -35-2-1.36 -46.0

Zn2+ +2e- ~ Zn(l)Zn(NH3)42++2e- ~ Zn(I)+4NH3

Zn(OH)42- +2e- ~ Zn(I)+40H-

665

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