Cov Tshuaj Tiv Thaiv Hauv Cov Cell Electrolytic
Lub cell electrolytic yog ib lub cuab yeej uas siv lub zog hluav taws xob los yuam kom muaj kev tshuaj lom neeg uas feem ntau yuav tsis tshwm sim yam tsis tau npaj tseg. Tsis zoo li cov cell galvanic (voltaic cells), uas tsim hluav taws xob los ntawm kev tshuaj lom neeg redox, cov cell electrolytic "siv" hluav taws xob los hloov cov tshuaj mus rau lwm yam los ntawm kev ua oxidation thiab txo cov txheej txheem. Cov thev naus laus zis no tseem ceeb heev hauv kev lag luam niaj hnub no, los ntawm kev plating hlau thiab kev ua tooj liab mus rau kev tsim hydrogen thiab oxygen roj thiab kev tsim txhuas. Lub luag haujlwm tseem ceeb ntawm lub cell electrolytic nyob hauv nws cov tshuaj lom neeg: kev hloov pauv ntawm cov khoom los ntawm kev siv hluav taws xob.
Cov Ntsiab Lus Tseem Ceeb: Redox Reactions thiab Electron Movement
Lub ntsiab lus ntawm electrolysis yog qhov redox (txo-oxidation). Oxidation yog kev tso tawm cov electrons, thaum txo qis yog qhov nce ntawm cov electrons. Hauv lub electrolytic cell, ib qho hluav taws xob sab nraud yuam kom cov electrons ntws los ntawm lub voj voog, ua rau qhov redox tshwm sim ntawm cov electrode nto.
Muaj ob lub electrodes tseem ceeb: lub anode thiab lub cathode. Hauv lub cell electrolytic, lub anode yog lub electrode qhov twg oxidation tshwm sim, thaum lub cathode yog lub electrode qhov twg txo qis tshwm sim. Qhov no feem ntau tsis meej pem vim tias hauv cov cell galvanic cov cim ntawm cov nqi electrode sib txawv, tab sis cov lus txhais ntawm oxidation ntawm lub anode thiab txo qis ntawm cathode yeej ib txwm sib xws rau txhua lub cell electrochemical.
Ib qho electrolyte yog ib qho nruab nrab uas coj tam sim no los ntawm kev txav ntawm cov ions. Electrolytes tuaj yeem yog cov kua ntsev, cov kua qaub, cov hauv paus, lossis cov tshuaj ionic uas yaj. Thaum tam sim no ntws, cov cations (cov ions uas them zoo) txav mus rau cathode kom dhau los ua kev txo qis, thaum cov anions (cov ions uas them tsis zoo) txav mus rau anode kom dhau los ua oxidation. Yog li, ntxiv rau qhov ntws ntawm cov electrons hauv lub voj voog sab nraud, muaj kev ntws ntawm cov ions hauv electrolyte kom tswj tau qhov sib npaug ntawm qhov them.
Cov Cheebtsam ntawm Electrolytic Cell thiab Lawv Lub Luag Haujlwm
Feem ntau, lub cell electrolytic muaj cov hauv qab no:
1. Kev muab hluav taws xob: muab qhov sib txawv ntawm qhov muaj peev xwm ua rau cov tshuaj tiv thaiv uas tsis yog los ntawm tus kheej tuaj yeem tshwm sim.
2. Ob lub electrodes: tuaj yeem yog cov electrodes inert (piv txwv li graphite lossis platinum) lossis cov electrodes nquag (piv txwv li tooj liab hauv kev ua kom tooj liab).
3. Electrolytes: cov tshuaj uas ionize kom lawv thiaj li khiav tau hluav taws xob.
4. Cov thawv thiab cov voj voog: ua kom lub kaw lus ruaj khov thiab tso cai rau kev soj ntsuam cov khoom ua haujlwm.
Qhov kev xaiv ntawm electrode thiab electrolyte txiav txim siab hom kev ua tshuaj tiv thaiv uas tshwm sim. Piv txwv li, ib lub inert electrode tsis koom nrog hauv kev ua tshuaj tiv thaiv stoichiometrically, thaum lub active electrode tuaj yeem yaj lossis precipitate ua ib feem ntawm kev ua tshuaj tiv thaiv.
Cov Tshuaj Tiv Thaiv ntawm Cathode: Cov Txheej Txheem Txo
Ntawm lub cathode, kev txo qis tshwm sim, txhais tau tias ib hom tshuaj tau txais cov electrons. Hauv cov kua dej, cov neeg sib tw rau kev txo qis feem ntau yog cov hlau cations lossis cov dej molecules (lossis hydrogen ions). Qhov kev tshuaj tiv thaiv uas tshwm sim nyob ntawm qhov kev txo qis ntawm txhua hom.
Piv txwv li:
1. Kev txo cov hlau ions
Piv txwv li, electrolysis ntawm CuSO₄ kua nrog inert electrodes:
\[
\text{Cu}^{2+} + 2e^- \rightarrow \text{Cu(s)}
\]
Cu²⁺ ions txais cov electrons thiab precipitate ua khoom tooj liab ntawm lub cathode.
2. Kev txo cov dej ua rau muaj hydrogen
Hauv cov tshuaj uas cov cations nyuaj rau txo (piv txwv li Na⁺ lossis K⁺ hauv dej), dej yooj yim dua los txo:
\[
2\text{H}_2\text{O} + 2e^- \rightarrow \text{H}_2(g) + 2\text{OH}^-
\]
Yog li ntawd, cov pa hydrogen raug tsim ntawm cathode, thiab cov tshuaj nyob ib puag ncig cathode dhau los ua qhov yooj yim dua vim yog kev tsim ntawm OH⁻.
Yog li, ntawm cathode, cov hlau deposition lossis cov pa roj tuaj yeem tshwm sim, nyob ntawm seb lub kaw lus zoo li cas.
Cov Tshuaj Tiv Thaiv ntawm Anode: Cov Txheej Txheem Oxidation
Ntawm qhov anode, oxidation tshwm sim, uas yog kev tso tawm ntawm cov electrons. Cov hom oxidizable feem ntau yog anions (xws li Cl⁻, Br⁻) lossis dej (tsim O₂). Ib yam li ntawm cathode, cov khoom ntawm qhov anode nyob ntawm hom ion thiab qhov yooj yim ntawm oxidation.
Piv txwv li:
1. Kev oxidation ntawm chloride ions tsim cov chlorine
Hauv electrolysis ntawm cov kua NaCl concentrated (brine), Cl⁻ anion tuaj yeem raug oxidized:
\[
2\text{Cl}^- \rightarrow \text{Cl}_2(g) + 2e^-
\]
Cov pa roj chlorine tau tsim nyob rau ntawm qhov anode.
2. Kev ua kom dej noo tawm ua rau muaj pa oxygen
Yog tias cov anion nyuaj rau oxidize (piv txwv li SO₄²⁻ lossis NO₃⁻), cov dej yuav raug oxidized:
\[
2\text{H}_2\text{O} \rightarrow \text{O}_2(g) + 4\text{H}^+ + 4e^-
\]
Cov pa oxygen raug tsim ntawm qhov anode, thiab cov tshuaj nyob ib puag ncig qhov anode dhau los ua acidic ntau dua vim yog kev tsim ntawm H⁺.
Qhov kev txiav txim siab ntawm "uas yog oxidized" ntawm lub anode feem ntau yog txiav txim siab los ntawm ion concentration, electrode hom, thiab kev ua haujlwm ntawm cov xwm txheej (voltage, pH, thiab overpotential).
Piv txwv tseem ceeb: Kev sib cais dej los ntawm hluav taws xob
Qhov electrolysis ntawm dej yog ib qho piv txwv zoo uas qhia txog kev ua haujlwm ntawm ob lub electrodes. Hauv kev xyaum, dej ntshiab yog tus neeg coj hluav taws xob tsis muaj zog heev, yog li ntawd cov electrolyte (piv txwv li, dilute H₂SO₄ lossis KOH) feem ntau raug ntxiv rau kom ua rau muaj kev coj hluav taws xob ntau dua.
Kev cuam tshuam ntawm cathode:
\[
2\text{H}_2\text{O} + 2e^- \rightarrow \text{H}_2(g) + 2\text{OH}^-
\]
Kev cuam tshuam ntawm anode:
\[
2\text{H}_2\text{O} \rightarrow \text{O}_2(g) + 4\text{H}^+ + 4e^-
\]
Yog tias cov electrons sib npaug thiab ntxiv rau, tag nrho cov tshuaj tiv thaiv yog:
\[
2\text{H}_2\text{O(l)} \rightarrow 2\text{H}_2(g) + \text{O}_2(g)
\]
Los ntawm qhov kev tshuaj tiv thaiv no nws tuaj yeem pom tias dej decomposes rau hauv hydrogen thiab oxygen roj nrog qhov ntim piv ntawm 2: 1, raws li stoichiometry ntawm qhov sib npaug ntawm cov tshuaj tiv thaiv.
Electrolysis ntawm NaCl kua: Kev tsim cov chlorine thiab sodium hydroxide
Hauv kev lag luam, ib qho ntawm cov txheej txheem electrolysis tseem ceeb tshaj plaws yog electrolysis ntawm cov tshuaj NaCl concentrated siv cov hlwb membrane lossis diaphragm. Cov tshuaj tiv thaiv uas tshwm sim yog:
Cathode:
\[
2\text{H}_2\text{O} + 2e^- \rightarrow \text{H}_2(g) + 2\text{OH}^-
\]
Anode:
\[
2\text{Cl}^- \rightarrow \text{Cl}_2(g) + 2e^-
\]
Tag nrho cov kev teb:
\[
2\text{NaCl(aq)} + 2\text{H}_2\text{O(l)} \rightarrow \text{Cl}_2(g) + \text{H}_2(g) + 2\text{NaOH(aq)}
\]
Cov txiaj ntsig muaj txiaj ntsig zoo heev: chlorine rau kev lag luam tshuaj lom neeg, hydrogen ua roj lossis cov khoom siv raw, thiab NaOH rau xab npum, ntawv, thiab ntau yam txheej txheem ntxuav.
Txoj Cai Faraday: Kev Sib Raug Zoo Ntawm Lub Nqi Hluav Taws Xob thiab Qhov Ntau Ntawm Cov Khoom
Cov tshuaj lom neeg hauv lub cell electrolytic muaj feem cuam tshuam nrog qhov ntau ntawm cov nqi hluav taws xob ntws. Faraday txoj cai hais tias qhov hnyav ntawm cov khoom tsim lossis decomposed ntawm lub electrode yog proportional rau qhov ntau ntawm cov nqi hluav taws xob (Q) hla dhau.
Kev them hluav taws xob:
\[
Q = Ix t
\]
nrog kuv tam sim no (amperes) thiab t lub sijhawm (vijtsam). Tus naj npawb ntawm moles ntawm electrons:
\[
n(e^-) = \frac{Q}{F}
\]
qhov twg F yog Faraday tus nqi tas mus li (≈ 96485 C/mol electrons). Los ntawm qhov no, peb tuaj yeem xam qhov hnyav ntawm cov hlau tso lossis qhov ntim ntawm cov roj tsim tawm raws li stoichiometry ntawm cov tshuaj tiv thaiv electrode. Qhov no yog vim li cas electrolysis thiaj li muaj txiaj ntsig zoo: cov khoom tuaj yeem kwv yees thiab tswj tau meej.
Cov Yam Cuam Tshuam Rau Cov Tshuaj Electrolysis
Qee yam tseem ceeb uas cuam tshuam rau cov tshuaj lom neeg hauv cov hlwb electrolytic yog:
1. Hom ion hauv electrolyte: txiav txim siab hom uas yuav raug txo / oxidized.
2. Kev sib sau ua ke ntawm cov ion: cov ions uas sib sau ua ke ntau dua feem ntau yooj yim koom nrog hauv kev tshuaj tiv thaiv.
3. Cov khoom siv hluav taws xob: inert vs active electrodes tuaj yeem tsim cov khoom sib txawv.
4. Qhov hluav taws xob thiab tam sim no: txiav txim siab qhov nrawm ntawm kev ua tshuaj tiv thaiv thiab qhov ua tau ntawm kev ua tshuaj tiv thaiv sab.
5. pH thiab kub: cuam tshuam rau qhov sib npaug thiab kinetics ntawm cov tshuaj tiv thaiv.
Kev tswj cov yam no yog qhov tseem ceeb rau cov txheej txheem electrolysis kom ua haujlwm tau zoo thiab tsim cov khoom xav tau.
Kev kaw
Cov tshuaj lom neeg hauv lub cell electrolytic yog ib qho piv txwv ntawm seb hluav taws xob tuaj yeem tswj kev hloov pauv ntawm cov khoom los ntawm cov txheej txheem redox. Ntawm cathode, kev txo qis tshwm sim, uas tuaj yeem tsim cov hlau precipitated lossis hydrogen roj, thaum ntawm anode, oxidation tshwm sim, uas tuaj yeem tsim cov chlorine lossis oxygen roj. Ntau daim ntawv thov kev lag luam ntawm electrolysis qhia tau hais tias cov txheej txheem no tsis yog tsuas yog lub tswv yim hauv chav kuaj xwb, tab sis lub hauv paus ntawm ntau yam tshuaj niaj hnub. Los ntawm kev nkag siab txog cov tshuaj tiv thaiv ntawm txhua lub electrode thiab cov yam ntxwv uas cuam tshuam rau lawv, peb tuaj yeem tsim cov txheej txheem electrolysis zoo dua, muaj kev nyab xeeb, thiab pheej yig dua.
