Imibuzo Yezibonelo kanye Nengxoxo Ye-Standard Electrode Potential
I-Pendahuluan
I-standard electrode potential ingumqondo obalulekile ku-electrochemistry ochaza ikhono le-electrode lokuheha ama-electron. Lo mqondo usetshenziswa ekubalweni kwamaseli e-electrochemical kanye nasekunqumeni ukuthambekela kokusabela kwe-redox. I-standard electrode potential (E°) ilinganiswa ngaphansi kwezimo ezijwayelekile, okungukuthi ekugxilweni okungu-1 M, ingcindezi engu-1 atm, kanye nokushisa okungu-25°C (298 K). Kulesi sihloko, sizoxoxa ngezibonelo eziningana zezinkinga ezijwayelekile ze-electrode potential futhi sixoxe ngazo ngokujulile.
Umqondo Oyisisekelo We-Standard Electrode Potential
Amandla e-electrode ajwayelekile, abizwa ngokuthi i-E°, achaza ukuthambekela kohlobo lwamakhemikhali okuncishiswa (ukwamukela ama-electron). Uma inani le-E° lihle kakhulu, kulapho ukuthambekela kohlobo okuncishiswa khona kukhulu. Ngokuphambene nalokho, lapho inani le-E° libi kakhulu, kulapho ukuthambekela kohlobo okuncishiswa khona kukhulu (ukulahlekelwa ama-electron).
Ithebula elijwayelekile le-electrode potential linikeza amanani e-E° ezindlela ezahlukahlukene zokusabela kwe-redox, futhi la manani asetshenziselwa ukubala amandla eseli e-electrochemical.
Isibonelo Umbuzo 1
Umbuzo:
Njengoba kunikezwe okulandelayo okulandelayo kwe-half-reaction kanye namandla azo e-electrode:
– Ag⁺(aq) + e⁻ → Ag(ama), E° = +0.80 V
– Cu²⁺(aq) + 2e⁻ → Cu(izi), E° = +0.34 V
Nquma amandla eseli (i-E°_cell) yeseli le-galvanic elakhiwe yilezi zindlela ezimbili zokusabela kwesigamu.
Ingxoxo:
Ukuze sinqume amandla eseli, sidinga ukuhlonza i-anode kanye ne-cathode. Kuseli le-galvanic, lelo elinamandla e-electrode ajwayelekile amahle kakhulu lisebenza njenge-cathode (indawo yokunciphisa) kanti lelo elinobubi kakhulu lisebenza njenge-anode (indawo yokushiswa).
1. Thola i-Anode ne-Cathode:
– Ag⁺ + e⁻ → Ag, E° = +0.80 V (okungcono kakhulu, ngakho-ke i-cathode)
– Cu²⁺ + 2e⁻ → Cu, E° = +0.34 V (negetive eyengeziwe, i-anode)
2. Thola Ukusabela Kwe-Oxidation Nokunciphisa:
– I-Cathode (ukunciphisa): Ag⁺ + e⁻ → Ag, E°_cathode = +0.80 V
– I-Anode (i-oxidation): I-Cu → I-Cu²⁺ + 2e⁻, I-E°_anode = -0.34 V (buyisela emuva indlela yokusabela kanye nesibonakaliso esingaba khona)
3. Ukubala i-E°_cell:
\[
E°_{cell} = E°_{cathode} – E°_{anode}
\]
\[
E°_{sel} = 0.80\, \text{V} – (-0.34\, \text{V})
\]
\[
I-E°_{sel} = 0.80\, \umbhalo{V} + 0.34\, \umbhalo{V} = 1.14\, \umbhalo{V}
\]
Ngakho-ke, amandla eseli (i-E°_cell) angu-+1.14 V.
Isibonelo Umbuzo 2
Umbuzo:
Njengoba kunikezwe ukusabela okungezansi ngamandla ayo e-electrode:
– Fe³⁺(aq) + e⁻ → Fe²⁺(aq), E° = +0.77 V
– Zn²⁺(aq) + 2e⁻ → Zn(s), E° = -0.76 V
Nquma amandla eseli (i-E°_cell) yeseli le-galvanic usebenzisa kokubili ukusabela okuyingxenye, bese ubhala ukusabela okuphelele kweseli.
Ingxoxo:
Njengangaphambili, kumele siqale sithole i-anode kanye ne-cathode.
1. Thola i-Anode ne-Cathode:
– Fe³⁺ + e⁻ → Fe²⁺, E° = +0.77 V (okungcono kakhulu, ngakho-ke i-cathode)
– Zn²⁺ + 2e⁻ → Zn, E° = -0.76 V (okungekuhle kakhulu, ngakho-ke i-anode)
2. Thola Ukusabela Kwe-Oxidation Nokunciphisa:
– I-Cathode (ukunciphisa): Fe³⁺ + e⁻ → Fe²⁺, E°_cathode = +0.77 V
– I-Anode (i-oxidation): I-Zn → I-Zn²⁺ + 2e⁻, I-E°_anode = -0.76 V (buyisela emuva indlela yokusabela kanye nesibonakaliso esingaba khona)
3. Ukulinganisa Ama-electron:
Ukusabela okuphelele kumele kulinganise inani lama-electron:
\[
2(\text{Fe}^{3+} + e⁻ → \text{Fe}^{2+})
\]
\[
\umbhalo{Zn} → \umbhalo{Zn}^{2+} + 2e⁻
\]
Ngakho-ke ukusabela okuphelele kweseli yilokhu:
\[
2\umbhalo{Fe}^{3+} + \umbhalo{Zn} → 2\umbhalo{Fe}^{2+} + \umbhalo{Zn}^{2+}
\]
4. Ukubala i-E°_cell:
\[
E°_{cell} = E°_{cathode} – E°_{anode}
\]
\[
E°_{sel} = 0.77\, \text{V} – (-0.76\, \text{V})
\]
\[
I-E°_{sel} = 0.77\, \umbhalo{V} + 0.76\, \umbhalo{V} = 1.53\, \umbhalo{V}
\]
Ngakho-ke, amandla eseli (i-E°_cell) angu-+1.53 V.
Isibonelo Umbuzo 3
Umbuzo:
Nikeza amandla eseli kanye nokusabela okuphelele kweseli kweseli le-galvanic usebenzisa ukusabela okulandelayo:
– MnO₂(ama) + 4H⁺(aq) + 2e⁻ → Mn²⁺(aq) + 2H₂O(l), E° = +1.23 V
– Cr³⁺(aq) + e⁻ → Cr²⁺(aq), E° = -0.50 V
Ingxoxo:
1. Thola i-Anode ne-Cathode:
– MnO₂ + 4H⁺ + 2e⁻ → Mn²⁺ + 2H₂O, E° = +1.23 V (enhle kakhulu, ngakho-ke i-cathode)
– Cr³⁺ + e⁻ → Cr²⁺, E° = -0.50 V (okungekuhle kakhulu, ngakho-ke i-anode)
2. Thola Ukusabela Kwe-Oxidation Nokunciphisa:
– I-Cathode (ukunciphisa): MnO₂ + 4H⁺ + 2e⁻ → Mn²⁺ + 2H₂O, E°_cathode = +1.23 V
– I-Anode (i-oxidation): I-Cr²⁺ → I-Cr³⁺ + e⁻, I-E°_anode = +0.50 V (buyisela emuva indlela yokusabela kanye nesibonakaliso esingaba khona)
3. Ukulinganisa Ama-electron:
Ukusabela okuphelele kumele kulinganise inani lama-electron:
\[
2(\text{Cr}^{3+} + e⁻ → \text{Cr}^{2+})
\]
\[
\umbhalo{MnO}_2 + 4\umbhalo{H}^+ + 2e⁻ → \umbhalo{Mn}^{2+} + 2\umbhalo{H}_2\umbhalo{O}
\]
Ngakho-ke ukusabela okuphelele kweseli yilokhu:
\[
\text{MnO}_2 + 4\text{H}^+ + 2\text{Cr}^{3+} → \text{Mn}^{2+} + 2\text{Cr}^{2+} + 2\text{H}_2\text{O}
\]
4. Ukubala i-E°_cell:
\[
E°_{cell} = E°_{cathode} – E°_{anode}
\]
\[
E°_{sel} = 1.23\, \text{V} – (-0.50\, \text{V})
\]
\[
I-E°_{sel} = 1.23\, \umbhalo{V} + 0.50\, \umbhalo{V} = 1.73\, \umbhalo{V}
\]
Ngakho-ke, amandla eseli (i-E°_cell) angu-+1.73 V.
Isiphetho
Ukuqonda amandla e-electrode ajwayelekile kubalulekile ku-electrochemistry ukuze kunqunywe izitayela zokusabela kwe-redox kanye namandla eseli e-electrochemical. Sisebenzisa izinyathelo okuxoxwe ngazo ngenhla, singabala kalula amandla eseli okusabela kwe-redox okunikeziwe. Amandla e-electrode ajwayelekile asetshenziselwa ukunquma i-anode kanye ne-cathode kuseli le-galvanic, kanye nokubala amandla eseli aphelele, okubonisa ukusebenza kahle kanye nesiqondiso sokusabela kwe-redox.
