Lipotso tsa Mehlala le Puisano ea Bokhoni ba Standard Electrode
Pendahuluan
Bokgoni bo tloaelehileng ba electrode ke mohopolo oa bohlokoa ho electrochemistry o hlalosang bokhoni ba electrode ho hohela lielektrone. Khopolo ena e sebelisoa lipalo tsa sele tsa electrochemical le ho fumana tšekamelo ea liketso tsa redox. Bokgoni bo tloaelehileng ba electrode (E°) bo lekanngoa tlas'a maemo a tloaelehileng, e leng ka mahloriso a 1 M, khatello ea 1 atm, le mocheso oa 25°C (298 K). Sehloohong sena, re tla buisana ka mehlala e 'maloa ea mathata a tloaelehileng a electrode' me re buisane ka ona ka botebo.
Khopolo ea Motheo ea Bokhoni ba Standard Electrode
Bokgoni bo tloaelehileng ba electrode, bo bontshwang e le E°, bo hlalosa tshekamelo ya mofuta wa dikhemikhale ya ho fokotswa (amohela dielektrone). Ha boleng ba E° bo le botle haholo, tshekamelo ya mofuta wa ho fokotswa e ba kgolo. Ka lehlakoreng le leng, ha boleng ba E° bo le bobe haholo, tshekamelo ya mofuta wa ho oxidation (ho lahlehelwa ke dielektrone) e ba kgolo.
Tafole e tloaelehileng ea matla a electrode e fana ka boleng ba E° bakeng sa likarabelo tse fapaneng tsa redox, 'me boleng bona bo sebelisoa ho bala matla a sele a electrochemical.
Mohlala oa Potso ea 1
Potso:
Ho latela likarabo tse peli tse latelang tsa halofo le matla a tsona a electrode:
– Ag⁺(aq) + e⁻ → Ag(li), E° = +0.80 V
– Cu²⁺(aq) + 2e⁻ → Cu(li), E° = +0.34 V
Fumana bokhoni ba sele (E°_cell) bakeng sa sele ea galvanic e entsoeng ke likarabelo tsena tse peli tsa halofo.
Puisano:
Ho fumana hore na sele e na le bokgoni bofe, re hloka ho hlwaya anode le cathode. Seleng ya galvanic, e nang le bokgoni ba electrode bo tloaelehileng bo nang le boleng bo botle e sebetsa jwalo ka cathode (sebaka sa phokotso) mme e nang le e mpe haholo e sebetsa jwalo ka anode (sebaka sa oxidation).
1. Hlalosa Anode le Cathode:
– Ag⁺ + e⁻ → Ag, E° = +0.80 V (e ntle haholoanyane, kahoo e cathode)
– Cu²⁺ + 2e⁻ → Cu, E° = +0.34 V (e mpe haholoanyane, kahoo anode)
2. Fumana Likarabelo tsa Oxidation le Fokotso:
– Cathode (phokotso): Ag⁺ + e⁻ → Ag, E°_cathode = +0.80 V
– Anode (oxidation): Cu → Cu²⁺ + 2e⁻, E°_anode = -0.34 V (khutlisa tataiso ea karabelo le letšoao le ka bang teng)
3. Ho bala sele ea E°_:
\[
E°_{sele} = E°_{cathode} – E°_{anode}
\]
\[
E°_{sel} = 0.80\, \text{V} – (-0.34\, \text{V})
\]
\[
E°_{sel} = 0.80\, \text{V} + 0.34\, \text{V} = 1.14\, \text{V}
\]
Kahoo, bokgoni ba sele (E°_cell) ke +1.14 V.
Mohlala oa Potso ea 2
Potso:
Ha ho nahanoa ka karabelo e ka tlase ka bokhoni ba eona ba electrode:
– Fe³⁺(aq) + e⁻ → Fe²⁺(aq), E° = +0.77 V
– Zn²⁺(aq) + 2e⁻ → Zn(s), E° = -0.76 V
Fumana bokhoni ba sele (E°_cell) bakeng sa sele ea galvanic u sebelisa li-half-reaction ka bobeli, 'me u ngole karabelo e felletseng ea sele.
Puisano:
Jwalo ka pele, re tlameha ho qala ka ho hlwaya anode le cathode.
1. Hlalosa Anode le Cathode:
– Fe³⁺ + e⁻ → Fe²⁺, E° = +0.77 V (e ntle haholoanyane, kahoo e cathode)
– Zn²⁺ + 2e⁻ → Zn, E° = -0.76 V (e mpe haholoanyane, kahoo anode)
2. Fumana Likarabelo tsa Oxidation le Fokotso:
– Cathode (phokotso): Fe³⁺ + e⁻ → Fe²⁺, E°_cathode = +0.77 V
– Anode (oxidation): Zn → Zn²⁺ + 2e⁻, E°_anode = -0.76 V (khutlisa tataiso ea karabelo le letšoao le ka bang teng)
3. Ho Leka-lekanya Lielektrone:
Karabelo e felletseng e lokela ho leka-lekanya palo ea lielektrone:
\[
2(\text{Fe}^{3+} + e⁻ → \text{Fe}^{2+})
\]
\[
\mongolo{Zn} → \mongolo{Zn}^{2+} + 2e⁻
\]
Kahoo karabelo e felletseng ea sele ke:
\[
2\mongolo{Fe}^{3+} + \mongolo{Zn} → 2\mongolo{Fe}^{2+} + \mongolo{Zn}^{2+}
\]
4. Ho bala sele ea E°_:
\[
E°_{sele} = E°_{cathode} – E°_{anode}
\]
\[
E°_{sel} = 0.77\, \text{V} – (-0.76\, \text{V})
\]
\[
E°_{sel} = 0.77\, \text{V} + 0.76\, \text{V} = 1.53\, \text{V}
\]
Kahoo, bokgoni ba sele (E°_cell) ke +1.53 V.
Mohlala oa Potso ea 3
Potso:
Fana ka bokgoni ba sele le karabelo e felletseng ya sele bakeng sa sele ya galvanic o sebedisa karabelo e latelang:
– MnO₂(s) + 4H⁺(aq) + 2e⁻ → Mn²⁺(aq) + 2H₂O(l), E° = +1.23 V
– Cr³⁺(aq) + e⁻ → Cr²⁺(aq), E° = -0.50 V
Puisano:
1. Hlalosa Anode le Cathode:
– MnO₂ + 4H⁺ + 2e⁻ → Mn²⁺ + 2H₂O, E° = +1.23 V (e ntle haholoanyane, kahoo e cathode)
– Cr³⁺ + e⁻ → Cr²⁺, E° = -0.50 V (e mpe ho feta, kahoo anode)
2. Fumana Likarabelo tsa Oxidation le Fokotso:
– Cathode (phokotso): MnO₂ + 4H⁺ + 2e⁻ → Mn²⁺ + 2H₂O, E°_cathode = +1.23 V
– Anode (oxidation): Cr²⁺ → Cr³⁺ + e⁻, E°_anode = +0.50 V (khutlisa tataiso ya karabelo le letshwao le ka bang teng)
3. Ho Leka-lekanya Lielektrone:
Karabelo e felletseng e lokela ho leka-lekanya palo ea lielektrone:
\[
2(\text{Cr}^{3+} + e⁻ → \text{Cr}^{2+})
\]
\[
\text{MnO}_2 + 4\text{H}^+ + 2e⁻ → \text{Mn}^{2+} + 2\text{H}_2\text{O}
\]
Kahoo karabelo e felletseng ea sele ke:
\[
\text{MnO}_2 + 4\text{H}^+ + 2\text{Cr}^{3+} → \text{Mn}^{2+} + 2\text{Cr}^{2+} + 2\text{H}_2\text{O}
\]
4. Ho bala sele ea E°_:
\[
E°_{sele} = E°_{cathode} – E°_{anode}
\]
\[
E°_{sel} = 1.23\, \text{V} – (-0.50\, \text{V})
\]
\[
E°_{sel} = 1.23\, \text{V} + 0.50\, \text{V} = 1.73\, \text{V}
\]
Kahoo, bokgoni ba sele (E°_cell) ke +1.73 V.
Qetello
Ho utloisisa bokgoni ba electrode bo tloaelehileng ho bohlokoa ho electrochemistry bakeng sa ho fumana mekhoa ea karabelo ea redox le bokhoni ba sele ea electrochemical. Re sebelisa mehato e boletsoeng ka holimo, re ka bala habonolo bokhoni ba sele ba karabelo e fanoeng ea redox. Matla a electrode a tloaelehileng a sebelisoa ho fumana anode le cathode ka seleng ea galvanic, hammoho le ho bala bokhoni bohle ba sele, e leng se bontšang bokhoni le tataiso ea karabelo ea redox.
