Cov Lus Nug Piv Txwv Kev Sib Tham Txog Cov Cell Electrochemical: Nkag Siab Txog Cov Ntsiab Lus Tseem Ceeb ntawm Electrochemistry Los Ntawm Cov Lus Nug Piv Txwv
Electrochemistry yog ib ceg ntawm chemistry uas kawm txog kev sib raug zoo ntawm cov tshuaj lom neeg thiab hluav taws xob tam sim no. Hauv electrochemistry, peb feem ntau tham txog ob hom cell tseem ceeb: galvanic (lossis voltaic) cell thiab electrolytic cell. Ob hom cell siv cov tshuaj redox los tsim lossis siv hluav taws xob.
Hauv tsab xov xwm no, peb yuav tham txog qee qhov piv txwv ntawm cov hlwb electrochemical uas yuav pab kom peb nkag siab tob txog lub tswv yim no.
1. Lo lus nug: Galvanic Cell
Piv txwv li, cia peb siv lub cell galvanic uas muaj lub electrode zinc (Zn) uas muab tso rau hauv cov kua ZnSO₄ thiab lub electrode tooj liab (Cu) uas muab tso rau hauv cov kua CuSO₄. Sau cov tshuaj tiv thaiv uas tshwm sim ntawm txhua lub electrode, nrog rau tag nrho cov tshuaj tiv thaiv hauv lub cell galvanic no.
Kev Sib Tham:
1. Kev tshuaj tiv thaiv ntawm lub zinc electrode (anode, oxidation):
Kev Tawm Tsam: \( Zn(s) \rightarrow Zn^{2+}(aq) + 2e^- \)
Ntawm no, zinc raug oxidized rau zinc ion (Zn²⁺) thiab tso tawm ob lub electrons.
2. Kev cuam tshuam ntawm lub electrode tooj liab (cathode, kev txo qis):
Reaction: \( Cu^{2+}(aq) + 2e^- \rightarrow Cu(s) \)
Ntawm no, cov ions tooj liab (Cu²⁺) txais ob lub electrons thiab raug txo kom ua cov tooj liab khov kho (Cu).
3. Kev cuam tshuam tag nrho hauv lub cell galvanic:
Muab ob qho kev sib xyaw ua ke no ua ke kom tau txais tag nrho cov tshuaj tiv thaiv:
\( Zn(s) + Cu^{2+}(aq) \rightarrow Zn^{2+}(aq) + Cu(s) \)
Feem ntau, nws tuaj yeem xaus lus tias hauv cov hlwb galvanic, qhov kev hloov pauv ntawm cov tshuaj redox yog siv los tsim hluav taws xob.
2. Lo lus nug: Lub peev xwm ntawm tes
Muab qhov peev xwm txo qis rau Zn²⁺/Zn = -0,76 V thiab Cu²⁺/Cu = +0,34 V. Xam lub peev xwm ntawm lub cell ntawm lub galvanic cell uas tau tham ua ntej.
Kev Sib Tham:
Lub peev xwm ntawm lub cell (E°_cell) tuaj yeem suav tau los ntawm kev siv cov qauv:
\[
E°_{cell} = E°_{cathode} – E°_{anode}
\]
Qhov twg:
- Lub cathode yog lub electrode qhov twg kev txo qis tshwm sim (Cu²⁺/Cu nrog E° = +0.34 V)
- Lub anode yog lub electrode qhov twg oxidation tshwm sim (Zn²⁺/Zn nrog E° = -0.76 V)
\[
E°_{sel} = 0.34\, V – (-0.76\, V) = 0.34\, V + 0.76\, V = 1.10\, V
\]
Yog li, lub peev xwm ntawm lub cell galvanic yog 1,10 V.
3. Lo lus nug: Electrolytic Cell
Hauv lub cell electrolytic, cov kua sodium chloride (NaCl) raug npaj rau hauv lub cell electrolytic nrog cov electrodes inert. Sau cov tshuaj tiv thaiv uas tshwm sim ntawm txhua lub electrode.
Kev Sib Tham:
Hauv lub cell electrolytic, hluav taws xob siv los tsav tsheb tsis yog spontaneous reaction. Hauv lub cell electrolytic nrog NaCl kua, peb muaj:
1. Kev tshuaj tiv thaiv ntawm cathode (kev txo qis):
\[
2H_2O(l) + 2e^- \rightarrow H_2(g) + 2OH^-(aq)
\]
Hauv feem ntau cov tshuaj NaCl uas yaj, dej yuav raug txo ua ntej sodium vim tias lub peev xwm txo qis ntawm dej zoo dua (-0.83 V) dua li sodium (-2.71 V).
2. Kev tshuaj tiv thaiv ntawm qhov anode (oxidation):
\[
2Cl^-(aq) \rightarrow Cl_2(g) + 2e^-
\]
Ntawm qhov anode, cov chloride ions raug oxidized rau cov roj chlorine.
3. Kev teb tag nrho:
Ua ke cov tshuaj tiv thaiv ntawm cathode thiab anode rau tag nrho cov tshuaj tiv thaiv:
\[
2H_2O(l) + 2Cl^-(aq) \rightarrow H_2(g) + Cl_2(g) + 2OH^-(aq)
\]
Hauv qhov kev electrolysis dej ntsev no, cov roj hydrogen thiab cov roj chlorine raug tsim ua ke nrog cov kua qaub (NaOH) vim yog kev sib cuam tshuam ntawm cov ions hauv cov kua qaub.
4. Lo lus nug: Faraday txoj cai ntawm Electrolysis
Yog tias muaj 2 faradays ntawm tam sim no hla dhau cov tshuaj, yuav muaj pes tsawg grams ntawm tooj liab los ntawm cov kua CuSO₄?
Kev Sib Tham:
Txoj cai lij choj ntawm Faraday hais tias qhov ntau ntawm cov khoom uas tso rau ntawm lub electrode thaum lub sijhawm electrolysis yog proportional rau qhov ntau ntawm cov hluav taws xob uas dhau los ntawm nws. Qhov hnyav ntawm cov khoom (m) tuaj yeem suav los ntawm kev siv cov qauv:
\[
m = \frac{M\cdot Q}{n\cdot F}
\]
Qhov twg:
- \(m\) yog qhov hnyav ntawm cov khoom tso tawm
- \(M\) yog qhov hnyav ntawm cov tshuaj (rau Cu, M = 63.5 g/mol)
- \(Q\) yog tus nqi ntawm cov nqi hluav taws xob (hauv coulombs, xam ua \(Q = n\cdot F\), qhov twg n yog tus lej ntawm faradays)
- \(n\) yog tus naj npawb ntawm cov moles ntawm cov electrons koom nrog hauv kev sib xyaw (rau Cu²⁺/Cu, n = 2)
- \(F\) yog Faraday tus nqi tas mus li (96500 C/mol)
Nrog 2 faraday tam sim no:
\[
m = 63.5 g/mol ∑2 = 96500 C/mol }
\]
Ua kom yooj yim dua qhov sib npaug:
\[
m = 63.5g
\]
Qhov tshwm sim yog tias 63.5 grams ntawm tooj liab tau tso los ntawm qhov electrolysis no.
Xaus
Kev nkag siab txog cov hlwb electrochemical yuav tsum muaj kev paub txog cov tshuaj redox, kev suav cov peev xwm ntawm cov hlwb, thiab electrochemical stoichiometry. Kev nkag siab txog cov teeb meem piv txwv zoo li qhov saum toj no yuav pab tau kom nkag siab meej txog cov ntsiab lus yooj yim thiab lawv daim ntawv thov hauv ntau hom hlwb electrochemical. Thaum kawg, txuas ntxiv xyaum nrog ntau yam teeb meem kom nkag siab tob dua, tshwj xeeb tshaj yog rau kev siv theoretical thiab kev xyaum ua haujlwm hauv ntau qhov chaw ntawm kev tshawb fawb thiab kev lag luam.
