Cov Lus Nug Piv Txwv Sib Tham Txog Kev Siv Cov Ntaub Ntawv Txog Qhov Muaj Peev Xwm ntawm Electrode
Lub peev xwm ntawm cov electrode txheem (E°) ua lub luag haujlwm tseem ceeb hauv chemistry, tshwj xeeb tshaj yog hauv kev nkag siab txog cov tshuaj redox thiab electrochemical. Nws muab txoj hauv kev los kwv yees qhov kev taw qhia ntawm cov tshuaj redox thiab piv cov zog ntawm cov neeg sawv cev oxidizing thiab txo qis. Tsab xov xwm no yuav nthuav qhia ntau qhov piv txwv ntawm kev siv cov ntaub ntawv peev xwm ntawm cov electrode txheem los piav qhia nws daim ntawv thov hauv cov xwm txheej tiag tiag.
Kev Taw Qhia Txog Cov Peev Xwm Electrode Txheem
Lub peev xwm ntawm electrode txheem ntsuas qhov kev nyiam ntawm ib qho khoom lossis cov khoom sib xyaw kom tau lossis poob electrons nyob rau hauv cov xwm txheej txheem (1 M, 1 atm, thiab 25 ° C). Lub peev xwm ntawm electrode txheem yog qhia hauv volts (V) thiab feem ntau piv rau lub peev xwm hydrogen electrode txheem (SHE), uas yog suav tias yog 0 V.
Piv Txwv Lo Lus Nug 1: Txheeb Xyuas Cov Kev Tshwm Sim Uas Tshwm Sim Sai Sai
Lo lus nug:
Xam seb cov tshuaj tiv thaiv no puas yuav tshwm sim yam tsis tau npaj tseg:
\[ \text{Zn}^{2+} + \text{Cu} \rightarrow \text{Zn} + \text{Cu}^{2+} \]
Cov qauv electrode potentials uas yuav tsum tau muaj yog:
– \(\text{Zn}^{2+} + 2e^{-} \rightarrow \text{Zn} \) \( E° = -0.76 \, \text{V} \)
- \(\text{Cu}^{2+} + 2e^{-} \rightarrow \text{Cu} \) \(E° = +0.34 \, \text{V} \)
Kev Sib Tham:
1. Txhais cov tshuaj tiv thaiv ib nrab ntawm lub hlwb:
Kev txo qis ib nrab ntawm cov hlwb:
– Kev sib xyaw ua ke ib nrab ntawm cov tshuaj tiv thaiv oxidation: \[\text{Zn}^{2+} + 2e^{-} \rightarrow \text{Zn} \, \text{(Kev txo, E° = -0.76 V)} \]
- Kev txo ib nrab ntawm cov tshuaj tiv thaiv: \[\text{Cu}^{2+} + 2e^{-} \rightarrow \text{Cu} \, \text{(Kev txo, E° = +0.34 V)} \]
2. Kev Txheeb Xyuas Qhov Ua Rau Muaj Kev Tshwm Sim:
Rov qab qhov kev sib xyaw uas muaj peev xwm qis dua kom nws dhau los ua oxidation:
– \[\text{Zn} \rightarrow \text{Zn}^{2+} + 2e^{-} \, \text{(Oxidation, E° = +0.76 V)} \]
Cov tshuaj tiv thaiv seem:
- \[\text{Cu}^{2+} + 2e^{-} \rightarrow \text{Cu} \, \text{(Reduction, E° = +0.34 V)} \]
3. Xam tag nrho E° (Lub peev xwm ntawm lub hlwb):
– \[ E°_{\text{cell}} = E°_{\text{reduction}} + E°_{\text{oxidation}} = +0.34 \, \text{V} + (+0.76 \, \text{V}) = +1.10 \, \text{V} \]
Vim tias lub peev xwm ntawm lub cell (E°_{\text{cell}}) yog qhov zoo, qhov kev tshuaj tiv thaiv no yog qhov tshwm sim yam tsis tau npaj tseg.
Piv txwv lus nug 2: Txheeb xyuas qhov muaj peev xwm sib npaug
Lo lus nug:
Xam lub peev xwm ntawm lub cell rau cov tshuaj tiv thaiv hauv qab no ntawm qhov kub thiab txias:
\[ \text{Fe}^{2+} + \text{Ag} \rightarrow \text{Fe} + \text{Ag}^{+} \]
Tus qauv electrode peev xwm:
– \(\text{Fe}^{2+} + 2e^{-} \rightarrow \text{Fe} \) \( E° = -0.44 \, \text{V} \)
– \(\text{Ag}^{+} + e^{-} \rightarrow \text{Ag} \) \( E° = +0.80 \, \text{V} \)
Kev Sib Tham:
1. Txhais cov tshuaj tiv thaiv ib nrab ntawm lub hlwb:
Kev txo qis ib nrab ntawm cov hlwb:
– \[\text{Fe}^{2+} + 2e^{-} \rightarrow \text{Fe} \, \text{(Kev Txo, E° = -0.44 V)} \]
– \[\text{Ag}^{+} + e^{-} \rightarrow \text{Ag} \, \text{(Kev Txo, E° = +0.80 V)} \]
2. Txheeb xyuas cov kev sib xyaw ua ke ib nrab:
Rov qab qhov kev tshuaj tiv thaiv uas muaj tus nqi tsis zoo me dua (zoo dua):
– \[\text{Fe} \rightarrow \text{Fe}^{2+} + 2e^{-} \, \text{(Oxidation, E° = +0.44 V)} \]
Cov tshuaj tiv thaiv seem:
– \[\text{Ag}^{+} + e^{-} \rightarrow \text{Ag} \, \text{(Kev Txo, E° = +0.80 V)} \]
3. Xam tag nrho E° (Lub peev xwm ntawm lub hlwb):
– \[ E°_{\text{cell}} = E°_{\text{reduction}} + E°_{\text{oxidation}} = +0.80 \, \text{V} + (+0.44 \, \text{V}) = +1.24 \, \text{V} \]
Lub peev xwm ntawm lub hlwb zoo qhia tau tias qhov kev tawm tsam no ua tiav yam tsis muaj kev cuam tshuam nyob rau hauv cov xwm txheej ib txwm muaj.
Piv txwv 3: Kev suav ntawm Gibbs Free Energy
Lo lus nug:
Txheeb xyuas qhov kev hloov pauv hauv Gibbs lub zog dawb (ΔG) rau cov tshuaj tiv thaiv hauv qab no:
\[ \text{Al} + \text{Cu}^{2+} \rightarrow \text{Al}^{3+} + \text{Cu} \]
Muab qhov peev xwm electrode txheem:
– \(\text{Al}^{3+} + 3e^{-} \rightarrow \text{Al} \) \( E° = -1.66 \, \text{V} \)
- \(\text{Cu}^{2+} + 2e^{-} \rightarrow \text{Cu} \) \(E° = +0.34 \, \text{V} \)
Kev Sib Tham:
1. Txhais cov tshuaj tiv thaiv ib nrab ntawm lub hlwb:
Kev txo qis ib nrab ntawm cov hlwb:
– \[\text{Al}^{3+} + 3e^{-} \rightarrow \text{Al} \, \text{(Kev Txo, E° = -1.66 V)} \]
- \[\text{Cu}^{2+} + 2e^{-} \rightarrow \text{Cu} \, \text{(Reduction, E° = +0.34 V)} \]
2. Kev Txheeb Xyuas Qhov Ua Rau Muaj Kev Tshwm Sim:
Rov qab qhov kev sib xyaw uas muaj peev xwm qis dua kom nws dhau los ua oxidation:
– \[\text{Al} \rightarrow \text{Al}^{3+} + 3e^{-} \, \text{(Oxidation, E° = +1.66 V)} \]
Cov tshuaj tiv thaiv seem:
- \[\text{Cu}^{2+} + 2e^{-} \rightarrow \text{Cu} \, \text{(Reduction, E° = +0.34 V)} \]
3. Kev Sib Npaug ntawm Cov Hluav Taws Xob:
Sib npaug tus naj npawb ntawm cov electrons rau cov tshuaj tiv thaiv:
– 2 \(\text{Al} \rightarrow 2\text{Al}^{3+} + 6e^{-} \) \[\text{(Oxidation, E° = +1.66 V)} \]
– 3 \(\text{Cu}^{2+} + 6e^{-} \rightarrow 3\text{Cu} \) \[\text{(Reduction, E° = +0.34 V)} \]
4. Xam tag nrho E° (Lub peev xwm ntawm lub hlwb):
– \[ E°_{\text{cell}} = (+0.34 \, \text{V} \times 3) + (+1.66 \, \text{V} \times 2) \]
Qhov yuam kev ntawm no: Qhov nruab nrab:
– \[ E°_{\text{cell}} = +0.34 \, \text{V} + +1.66 \, \text{V} = +2.00 \, \text{V}\]
5. Xam ΔG:
Cov Qauv: \(\Delta G = -nFE_{\text{cell}}\)
– \[n = 6 \, \text{electrons} \]
– \[F = 96485 \, \text{C/mol} \]
– \[ \Delta G = -6 \times 96485 \, \text{C/mol} \times +2.00 \, \text{V}\]
- \[= -1157820 \, \text{J/mol} \]
- \[ = -1157.82 \, \text{kJ/mol}\]
Yog li, qhov ΔG tsis zoo qhia tias qhov kev tshuaj tiv thaiv no yog spontaneous.
Xaus
Cov ntaub ntawv txog lub zog ntawm electrode txheem muab ib txoj hauv kev siv tau los kwv yees seb qhov kev hloov pauv redox yuav mus li cas, nws yuav mus li cas, thiab nws txoj kev sib raug zoo rau qhov kev hloov pauv ntawm Gibbs lub zog dawb. Qhov teeb meem piv txwv saum toj no qhia txog yuav ua li cas cov ntaub ntawv no tuaj yeem siv los txiav txim siab qhov kev hloov pauv ntawm redox thiab kev suav lub zog cuam tshuam. Rau cov tub ntxhais kawm lossis leej twg kawm chemistry, kev nkag siab txog cov ntaub ntawv txog lub zog ntawm electrode txheem thiab nws cov ntawv thov yog lub hauv paus tseem ceeb rau kev nkag siab txog cov kev hloov pauv electrochemical nyuaj dua.
