Cov Lus Nug Piv Txwv thiab Kev Sib Tham Txog Qhov Muaj Peev Xwm ntawm Electrode Txheem
Pendahuluuan
Lub peev xwm ntawm electrode txheem yog ib lub tswv yim tseem ceeb hauv electrochemistry uas piav qhia txog lub peev xwm ntawm electrode los nyiam cov electrons. Lub tswv yim no yog siv rau hauv kev suav electrochemical cell thiab hauv kev txiav txim siab qhov propensity rau redox reactions. Lub peev xwm ntawm electrode txheem (E°) yog ntsuas nyob rau hauv cov xwm txheej txheem, uas yog ntawm qhov concentration ntawm 1 M, lub siab ntawm 1 atm, thiab qhov kub ntawm 25 ° C (298 K). Hauv tsab xov xwm no, peb yuav tham txog ntau qhov piv txwv ntawm cov teeb meem peev xwm ntawm electrode txheem thiab tham txog lawv kom tob.
Lub Tswv Yim Tseem Ceeb ntawm Lub Peev Xwm Electrode Txheem
Tus qauv electrode potential, uas yog E°, piav qhia txog qhov uas ib hom tshuaj lom neeg yuav raug txo (txais cov electrons). Tus nqi E° zoo dua, qhov ntau dua ntawm cov hom yuav raug txo. Ntawm qhov tod tes, tus nqi E° tsis zoo dua, qhov ntau dua ntawm cov hom yuav raug oxidized (poob cov electrons).
Lub rooj qhia txog lub peev xwm ntawm electrode muab cov nqi E° rau ntau yam kev tshuaj tiv thaiv redox, thiab cov nqi no yog siv los xam cov peev xwm ntawm electrochemical cell.
Piv txwv lus nug 1
Lo lus nug:
Muab ob qho kev sib xyaw ua ke thiab lawv cov peev xwm electrode hauv qab no:
– Ag⁺(aq) + e⁻ → Ag(s), E° = + 0.80 V
- Cu²⁺(aq) + 2e⁻ → Cu(s), E° = +0.34 V
Txheeb xyuas lub peev xwm ntawm lub cell (E°_cell) rau lub cell galvanic uas tsim los ntawm ob lub ib nrab-tshuaj no.
Kev Sib Tham:
Yuav kom paub txog lub peev xwm ntawm lub cell, peb yuav tsum txheeb xyuas lub anode thiab cathode. Hauv lub cell galvanic, lub uas muaj lub peev xwm electrode zoo dua ua haujlwm ua cathode (qhov chaw txo qis) thiab lub uas muaj lub peev xwm tsis zoo dua ua anode (qhov chaw oxidation).
1. Txheeb xyuas Anode thiab Cathode:
– Ag⁺ + e⁻ → Ag, E° = +0.80 V (zoo dua, yog li cathode)
- Cu²⁺ + 2e⁻ → Cu, E° = + 0.34 V (ntau qhov tsis zoo, yog li anode)
2. Txheeb Xyuas Cov Kev Tshwm Sim Oxidation thiab Reduction:
– Cathode (kev txo): Ag⁺ + e⁻ → Ag, E°_cathode = +0.80 V
– Anode (oxidation): Cu → Cu²⁺ + 2e⁻, E°_anode = -0.34 V (rov qab qhov kev taw qhia ntawm cov tshuaj tiv thaiv thiab cov cim qhia txog peev xwm)
3. Xam E°_cell:
\[
E°_{cell} = E°_{cathode} – E°_{anode}
\]
\[
E°_{sel} = 0.80\, \text{V} – (-0.34\, \text{V})
\]
\[
E°_{sel} = 0.80\, \text{V} + 0.34\, \text{V} = 1.14\, \text{V}
\]
Yog li, lub peev xwm ntawm lub cell (E°_cell) yog +1.14 V.
Piv txwv lus nug 2
Lo lus nug:
Muab cov tshuaj tiv thaiv hauv qab no nrog nws lub peev xwm electrode:
– Fe³⁺(aq) + e⁻ → Fe²⁺(aq), E° = +0.77 V
– Zn²⁺(aq) + 2e⁻ → Zn(s), E° = -0.76 V
Txheeb xyuas lub peev xwm ntawm lub cell (E°_cell) rau lub cell galvanic siv ob qho tib si ib nrab-reactions, thiab sau tag nrho cov cell reaction.
Kev Sib Tham:
Ib yam li ua ntej, peb yuav tsum xub txheeb xyuas qhov anode thiab cathode.
1. Txheeb xyuas Anode thiab Cathode:
– Fe³⁺ + e⁻ → Fe²⁺, E° = +0.77 V (zoo dua, yog li cathode)
– Zn²⁺ + 2e⁻ → Zn, E° = -0.76 V (tsis zoo dua, yog li ntawd anode)
2. Txheeb Xyuas Cov Kev Tshwm Sim Oxidation thiab Reduction:
– Cathode (kev txo): Fe³⁺ + e⁻ → Fe²⁺, E°_cathode = +0.77 V
– Anode (oxidation): Zn → Zn²⁺ + 2e⁻, E°_anode = -0.76 V (rov qab qhov kev taw qhia ntawm cov tshuaj tiv thaiv thiab cov cim qhia txog peev xwm)
3. Kev Sib Npaug ntawm Cov Hluav Taws Xob:
Tag nrho cov tshuaj tiv thaiv yuav tsum sib npaug tus naj npawb ntawm cov electrons:
\[
2(\text{Fe}^{3+} + e⁻ → \text{Fe}^{2+})
\]
\[
\text{Zn} → \text{Zn}^{2+} + 2e⁻
\]
Yog li ntawd, qhov kev ua haujlwm ntawm lub cell tag nrho yog:
\[
2\text{Fe}^{3+} + \text{Zn} → 2\text{Fe}^{2+} + \text{Zn}^{2+}
\]
4. Xam E°_cell:
\[
E°_{cell} = E°_{cathode} – E°_{anode}
\]
\[
E°_{sel} = 0.77\, \text{V} – (-0.76\, \text{V})
\]
\[
E°_{sel} = 0.77\, \text{V} + 0.76\, \text{V} = 1.53\, \text{V}
\]
Yog li, lub peev xwm ntawm lub cell (E°_cell) yog +1.53 V.
Piv txwv lus nug 3
Lo lus nug:
Muab lub peev xwm ntawm lub cell thiab cov tshuaj tiv thaiv ntawm lub cell rau lub cell galvanic siv cov tshuaj tiv thaiv no:
– MnO₂(s) + 4H⁺(aq) + 2e⁻ → Mn²⁺(aq) + 2H₂O(l), E° = +1.23 V
- Cr³⁺(aq) + e⁻ → Cr²⁺(aq), E° = -0.50 V
Kev Sib Tham:
1. Txheeb xyuas Anode thiab Cathode:
– MnO₂ + 4H⁺ + 2e⁻ → Mn²⁺ + 2H₂O, E° = +1.23 V (zoo dua, yog li cathode)
– Cr³⁺ + e⁻ → Cr²⁺, E° = -0.50 V (tsis zoo dua, yog li ntawd anode)
2. Txheeb Xyuas Cov Kev Tshwm Sim Oxidation thiab Reduction:
- Cathode (txo): MnO₂ + 4H⁺ + 2e⁻ → Mn²⁺ + 2H₂O, E°_cathode = +1.23 V
– Anode (oxidation): Cr²⁺ → Cr³⁺ + e⁻, E°_anode = +0.50 V (rov qab qhov kev taw qhia ntawm cov tshuaj tiv thaiv thiab cov cim qhia txog peev xwm)
3. Kev Sib Npaug ntawm Cov Hluav Taws Xob:
Tag nrho cov tshuaj tiv thaiv yuav tsum sib npaug tus naj npawb ntawm cov electrons:
\[
2(\text{Cr}^{3+} + e⁻ → \text{Cr}^{2+})
\]
\[
\text{MnO}_2 + 4\text{H}^+ + 2e⁻ → \text{Mn}^{2+} + 2\text{H}_2\text{O}
\]
Yog li ntawd, qhov kev ua haujlwm ntawm lub cell tag nrho yog:
\[
\text{MnO}_2 + 4\text{H}^+ + 2\text{Cr}^{3+} → \text{Mn}^{2+} + 2\text{Cr}^{2+} + 2\text{H}_2\text{O}
\]
4. Xam E°_cell:
\[
E°_{cell} = E°_{cathode} – E°_{anode}
\]
\[
E°_{sel} = 1.23\, \text{V} – (-0.50\, \text{V})
\]
\[
E°_{sel} = 1.23\, \text{V} + 0.50\, \text{V} = 1.73\, \text{V}
\]
Yog li, lub peev xwm ntawm lub cell (E°_cell) yog +1.73 V.
Xaus
Kev nkag siab txog cov peev xwm ntawm cov electrode txheem yog qhov tseem ceeb hauv electrochemistry rau kev txiav txim siab txog cov qauv tshuaj redox thiab cov peev xwm ntawm cov cell electrochemical. Siv cov kauj ruam uas tau tham saum toj no, peb tuaj yeem yooj yim xam cov peev xwm ntawm cov cell ntawm cov tshuaj redox. Cov peev xwm ntawm cov electrode txheem yog siv los txiav txim siab qhov anode thiab cathode hauv lub cell galvanic, nrog rau kev xam tag nrho cov peev xwm ntawm cov cell, uas qhia txog kev ua haujlwm thiab kev coj ntawm cov tshuaj redox.
