Njikọ, njikọ, njikọ?

Mmekọrịta ya na Electrochemistry Part 5

N'oge nzukọ ndị gara aga, ewebata anyị na ọtụtụ ihe atụ nke mkpụrụ ndụ voltaic - ụfọdụ mkpa akụkọ ihe mere eme na ndị ọzọ eji eme ihe taa. Ụwa nke mkpụrụ ndụ bara ụba nke ukwuu, ya mere ọ bụ oge iwebata usoro ndị ọzọ karịa nke egosiri ugbu a.

Ndị na-abụghị ọla nwekwara ike ịbụ ọkara sel

Nke mbụ, nnwale nke chọrọ electrodes graphite abụọ sitere na ihe ndị Leclanchet nọrọ, zinc bromide ZnBr.₂, ike ọkọnọ (dị ka batrị 4,5V) na mita voltaji dị mkpa. N'ime ụlọ nyocha ụlọ, n'ezie, anyị agaghị ahụ nnu zinc akwadoro, ma n'ọnọdụ anyị, a ga-eji ngwakọta nke potassium bromide KBr na zinc sulfate (VI) ZnSO dochie ya nke ọma.₄. Anyị na-agbakọta otu setịpụrụ nke nwere osisi graphite abụọ, gbanye ya na osisi ka electrodes na-emikpu n'ime iko.

Anyị na-etinye mpempe wires na electrodes, ọkacha mma na ígwè na-ere ahịa (ya mere, mgbe ị na-ewepụ ha na batrị ochie, hapụ bras "okpu" na mkpanaka graphite). Anyị ga-emekwa diaphragm site na mpempe kaadiboodu nwere akụkụ ndị a na-emegharị na beaker nwere ikike nke 50-100 cm.³ (a nwekwara ike iji pin maapu kaadiboodu).

Ugbu a, anyị na-agbaze ụfọdụ nnu ndị a kpọtụrụ aha na mmiri, wee jupụta iko ahụ na ngwọta a kwadebere (nleba anya 5-10%). Debe akwa ahụ na electrodes na nsọtụ nke arịa ahụ, ma tinye nsọtụ nke wires na efere ọla nke batrị dị larịị (polarity adịghị mkpa n'oge a) ma lelee usoro wuru.

Ihe fọrọ nke nta ka ọ bụrụ ozugbo, a na-edobe oyi akwa na-egbuke egbuke ọlaọcha-acha ntụ ntụ na electrode ejikọrọ na njedebe na-adịghị mma nke batrị ahụ. Ejiri zinc ọla mee ya. A na-ahụ agba na-acha odo odo-aja aja nke ngwọta n'akụkụ electrode nke abụọ ejikọrọ na mkpanaka dị mma nke batrị ahụ. Bromine efu na-acha agba n'akụkụ mkpanaka graphite. Mgbe ihe dị ka nkeji 5 gachara, kwụpụ wires na ọdụ batrị. N'iji voltmeter, tụọ voltaji ("mwepu" nke mita na-ejikọta ya na electrode kpuchie na oyi akwa ígwè).

Na-abanyeghị na usoro na-eme n'oge electrolysis (anyị ga-atụle ha na otu n'ime ndị na-esonụ nzukọ), anyị nwere ike ikwubi na kere cell mejupụtara abụọ electrodes: zinc (metal zinc edebe na graphite na ngwọta nke Zn).²⁺) na bromine (ihe ngwọta nke ion free bromine na bromide Br^?). Carbon bụ naanị onye na-eduzi ọkụ eletrik (na omume, ihe ndị na-adịghị emeghachi omume n'okpuru ọnọdụ ụfọdụ, dị ka graphite, platinum, na-ejikarị eme ihe dị ka ihe electrode).

Ka anyị jikọọ ihe nnata ugbu a na electrodes? bọlbụ ọkụ nwere voltaji na-arụ ọrụ nke 1,5 V (na nke a, polarity nke njikọ adịghịkwa mkpa). Dị ka ike na-ewepụtara na usoro, anyị na-ahụ na-eji nwayọọ nwayọọ efu nke metal nkwụnye ego na otu electrode na-acha odo odo na nke ọzọ. Ihe ndị ewepụtara na mbụ na-emeghachi omume, na-eweghachi ọnọdụ mbụ ha. Mmeghachi omume na-apụtachaghị ìhè na nnyefe nke eletrọn site na njikọ waya. Nke a bụ isi ihe dị na sel galvanic.

Gịnị mmeghachi omume mere na usoro anyị? Maka zinc electrode, anyị nwere ike inye usoro nhazi usoro:

 (-)Zn⁰ ? zinc²⁺ + 2e^-

Na electrode nke abụọ, a na-ebelata bromine free ka ọ bụrụ bromine anions:

 (+) Mba.₂ + 2e^- , 2 pcs^-

Ya mere, atụmatụ cell bụ nke a (anyị na-ahapụ potassium na sulfate (VI) ion, nke na-adịghị etinye aka na mmeghachi omume):

 (-) С, Zn | ZnBr2aq? ZnBr2aq | С(+)

Anyị ekwesịghị iji oghere na cell. Otú ọ dị, iji ya mee ihe ga-egbochi bromine ịkwaga n'akụkụ electrode nwere zinc ma na-emeghachi omume n'etiti sel.

Ndị na-abụghị ọla na-etolite ọkara sel dị ka ihe ọla. Ọ dị mkpa naanị iji onye nduzi na-emikpu n'ime ngwọta kwesịrị ekwesị, nke ga-ekere òkè na nnyefe nke electrons. Maka halogens, ikike ọkọlọtọ bụ ndị a (mmeghachi omume electrode yiri nke enyere maka bromine):

Ọkara cell	F2/F?	Cl2/Cl?	Br2/Br?	I2/I?
E0 [V]	+ 2,87	+ 1,36	+ 1,07	+ 0,54

N'ihe gbasara fluorine, a na-agbakọ uru nwere ike (nke kachasị elu nke ọkara sel niile) , ọ bụghị tụọ. Ihe kpatara ya, dị ka ọ dị na alkali na alkaline ụwa ọla, bụ mmeghachi omume nke mmewere na-arụ ọrụ na mmiri.

cell redox

Maka nnwale ọzọ, anyị ga-akwadebe ihe ngwọta ndị a: ígwè (III) chloride, FeCl₃ na ntinye nke 5%, potassium iodide KI na ntinye nke 10% na nkwusioru starch mmiri. Gwakọta cm ole na ole n'ime tube ule³ ngwọta nnu, ma mgbe obere oge gasịrị, tinye ntakịrị tụlee nke starch nkwusioru. Agba acha anụnụ anụnụ nke ọdịnaya na-egosi ọnụnọ nke ayodiin efu. Edere mmeghachi omume a site na nha anya:

 2 Fe³⁺ + 2m^- ? 2 Fe²⁺ + m₂

iron (III) cations oxidize iodide anions ka ọ bụrụ mmewere efu, na-ebelata ka ion iron (II).

Mgbanwe na agba nke ihe ngosi starch gosipụtara ọnụnọ nke irighiri ayodiin, mana a na-emepụta cations Fe n'ezie?²⁺? Ka anyị nwalee echiche a. Nnwale e ji mara maka nchọpụta ígwè (II) cations bụ mmeghachi omume na potassium hexacyanoferrate (III) K.₃[Fe(CN)₆], nke a na-akpọkarị potassium ferricyanide. Ngwakọta ahụ na-etolite kristal na-acha uhie uhie, n'ụzọ dị iche na potassium ferrocyanide nke otu aha (potassium (II) hexacyanoferrate K.₄[Fe(CN)₆]) nwere kristal edo edo ? ka anyị ghara ịgbagha mmekọrịta abụọ a. Ka anyị kwugharịa nnwale gara aga, mana kama nkwusioru starch, anyị ga-agbakwunye ntakịrị tụlee nke ngwọta 1% nke potassium ferricyanide. Ọzọkwa, ọdịnaya nke arịa mmeghachi omume na-atụgharị na-acha anụnụ anụnụ n'ihi ngwakọta mgbagwoju anya a na-akpọ Turnbull's blue:

 3 Fe²⁺ + 2 [Fe (CN)₆]^3- ? Okwukwe₃[Fe(CN)₆]₂

Ana m akwado ka ndị na-ekweghị ekwe mee nnwale na nnu nke ígwè ferrous na ferric. Anyị na-enweta tint na-acha anụnụ anụnụ naanị n'ihe banyere nke mbụ.

Ugbu a, na obere beakers abụọ nwere ikike nke 50-100 ml, wụsa ọtụtụ ngwọta nke ígwè (III) chloride na potassium iodide.³. Na nke ọ bụla n'ime arịa, na-emikpu a graphite electrode na a waya agbakwunyere (tinye n'elu kwesịrị ekwesị nkwụnye ka ọ ghara ịdaba n'ime iko). Ọzọkwa, tinye ntakịrị nkwusioru starch na arịa nwere ngwọta nke potassium iodide. Iji mepụta cell, ị ga-achọkwa igodo electrolytic (mere n'oge otu n'ime nzukọ ndị gara aga? Mpempe akwụkwọ na-ehichapụ nke etinyere na ngwọta nke KNO zuru ezu.₃). A na-ejikọta njedebe nke ndị na-eduga site na electrodes na njedebe nke mita eluigwe na ala arụnyere iji tụọ voltaji.

Anyị na-ekpebi polarity nke voltmeter njikọ onwe anyị na ndabere nke nyocha nke nhata maka mmeghachi omume nke ígwè (III) cations na ayodiin anions, anyị na-ahụ nke ion ha na-enye na nke na-enweta electrons. Ọgụgụ mita na-akwado ọrụ nke cell galvanic. Mgbe ahụ, anyị na-atụgharị ngwaọrụ ahụ na nha dị ugbu a. Ọ dị ntakịrị (nke usoro nke ọtụtụ iri mA), n'ihi ya, anyị adịghị mkpa iji ihe ọ bụla nnata ọzọ (dịka ọmụmaatụ, bọlbụ ọkụ) iji chebe ngwaọrụ ahụ site na mmebi. Nhazi nke agba anụnụ anụnụ gbara ọchịchịrị gburugburu electrode emikpu n'ime beaker nwere ngwọta nke potassium iodide na-agba akaebe na mmeghachi omume na usoro ahụ. Kedu mgbe anyị ga-agbakwunye ntakịrị potassium ferricyanide ngwọta na ígwè (III) nnu shaker? nakwa na ya. Ka anyị detuo nha nke usoro na-eme na iko:

 (-)2 I^- ? ₂ + 2e^-

(+) 2F³⁺ + 2e^- ? 2 Fe²⁺ 

 na eserese cell:

(-) Na | CI_aq || FeCl_3aq | C (+)

Otu mmeghachi omume ahụ na-ewere ọnọdụ na cell dị ka mgbe ịgwakọta ihe ndị ahụ na tube ule (o zuru ezu ịgbakwunye usoro anodic na cathodic site n'akụkụ), na nkewa nke oghere nke mgbanwe na-eme ka o kwe omume iji ike nke electrons na-ebufe. n'etiti halves nke cell.

A na-akpọ cell cell anyị na-ewu redox cell. Aha a na-ahụkarị mana ọ na-eduhie eduhie. E kwuwerị, anyị maara na usoro nke oxidation na mbelata na-eme na njikọ ọ bụla. Kedu otu esi achọpụta ntụziaka nke mmeghachi omume redox (emere ma na cell ma na tube ule)? Usoro a dị mfe:

1. Na tebụl anụ ahụ na nke kemịkalụ, ànyị na-ahụ ike ọkọlọtọ nke ọkara sel kwekọrọ? maka sistemu Fe³⁺/ Okwukwe²⁺ nke a bụ +0,77 V; maka m₂/I^?: +0,54V.

2. Usoro nke nwere ikike dị elu bụ onye na-ahụ maka oxidizing na mmeghachi omume (cell-cathode), na ọkara cell nwere ike dị ala? anode nke cell, i.e. onye na-ebelata ihe.

3. Otú ọ dị, e kwesịrị icheta na n'ihi na usoro na a obere ọdịiche na ụkpụrụ nke ọkọlọtọ potentials, n'ọnọdụ ụfọdụ, ọrụ nwere ike gbanwee (ezigbo potentials dabere, n'etiti ihe ndị ọzọ, na ịta nke reagents).

Mmanụ ụgbọala

Anyị ga-agbakọta usoro site na nnwale mbụ, dochie naanị ngwọta nke potassium bromide na zinc sulfate (VI) na ngwọta 10% nke sulfuric acid (VI) H.₂SO₄. Mgbe 1-2 nkeji nke electrolysis (na-eme na ntọhapụ nke gas na electrodes), gbanyụọ ike isi iyi na nke ọma, ka ị ghara wepụ gas egosipụta na graphite elu, tụọ voltaji na voltmeter. Njikọ emepụtara! Mgbe ịgbanwee ngwaọrụ ahụ na ọnọdụ nha dị ugbu a, mmadụ nwere ike ịhụ mwepu nke ikuku gas n'elu electrodes graphite n'oge mmeghachi omume. Na-abanyeghị na nkọwa nke usoro nke kpatara ntinye nke oxygen na hydrogen na electrodes, mmeghachi omume dị na cell bụ ndị a:

 (-) 2H2? awa 4⁺ + 4e^-

(+) Ndị₂ + 4 awa⁺ + 4e^- ? 2h₂O

Na mkpokọta, mmeghachi omume nke njikọ mmiri sitere na ihe ndị ahụ na-ewere ọnọdụ.

Sistemụ arụrụ arụ bụ ụdị mmanụ ọkụ. Ntughari ozugbo nke ike nke mmeghachi omume n'etiti mmanụ ọkụ na oxidizer n'ime ọkụ eletrik bara uru nke ukwuu site n'echiche nke akụ na ụba nke usoro ahụ? Ọ dịghị mkpa ịgbanwe okpomọkụ nke combustion n'ime ike uzuoku, nke na-ebu naanị turbines. Ọ bụghị ihe mgbagwoju anya, a na-emepụta usoro ndị dị otú ahụ iji dozie nsogbu ike (na ihe mkpofu bụ mmiri dị ọcha). Otú ọ dị, ọnụ ahịa ihe owuwu ụlọ na mkpa ịmepụta hydrogen bụ nnukwu ihe mgbochi.

Ọ bụ ezie na a na-eji mkpụrụ ndụ mmanụ ọkụ na-emepụta ọkụ eletrik na mpaghara kachasị elu nke nkà na ụzụ, dị ka ụgbọ elu mbara igwe (n'ụfọdụ ụlọ ọrụ, ụgwọ na-arụ ọrụ nke abụọ), akụkọ ihe mere eme ha dị ogologo. Ọ bụ onye Britain na-emepụta ihe bụ William Robert Grove wuru ụdị ọrụ mbụ nke cell hydrogen-oxygen na 1839.

Isiokwu a na-enye ụdị njikọ dị iche iche, dị iche na nke a tụlere na nzukọ ndị gara aga. Dị ka akụkụ ndị ọzọ? naanị nsogbu nke usoro ndị a, nke dị mkpa ọ bụghị naanị dị ka isi iyi nke ike, ka akọwapụtara. Otú ọ dị, mkpa ọ dị ịnọgide na-enwe ederede ederede kwesịrị ekwesị na-eme ka ọ ghara ikwe omume ikwurịta ọtụtụ isiokwu ndị na-adọrọ mmasị metụtara njikọ (M na-agba ndị na-agụ akwụkwọ ume ka ha chọọ ozi n'onwe ha). N'ime ihe omume na-esote nke okirikiri, anyị ga-enyocha tebụl nke ikike ọkara-cell. A ga-enwekwa onyinye nke ahụmịhe na-atọ ụtọ.

ngwa eletrọnịkị

cell redox

Mkpụrụ ndụ electrochemical ọ bụla na-enweta oxidation (na anode) na mbelata (na cathode). Agbanyeghị, na jargon kemịkalụ, a na-akpọ sel redox dị ka ụfọdụ ụdị sistemụ.

Maka nnwale ahụ, a chọrọ ngwọta nke potassium iodide KI na iron (III) chloride FeCl.₃ na aqueous nkwusioru nke starch (ntụ ọka nduku). Ị ga-achọkwa igodo electrolytic jupụtara na ngwọta nke potassium nitrate (V) KNO₃. Ọ bụrụ na anyị enweghị isi, ọ ga-ezuru mpịaji ọtụtụ ugboro a warara nke anụ ahụ akwụkwọ ma ọ bụ a owu eri tinye ya na ngwọta nke potassium nitrate.

Anyị ga-eji mkpanaka graphite sitere na mkpụrụ ndụ Leclanche ejiri mee ihe dị ka electrodes (foto 1). Jiri waya jiri obere okirikiri mechie nsọtụ nke electrodes ma tinye ha na beaker na ngwọta KI (na mgbakwunye nke starch slurry) na FeCl.₃. Ọzọkwa, anyị na-ejikọta ihe ngwọta na iko na igodo electrolytic ma ọ bụ otu n'ime ihe dochie ya (foto 2). Mgbe oge ụfọdụ gasịrị, streaks na-acha odo odo na-amalite ịpụta n'ime iko na ngwọta potassium iodide (foto 3), jiri nwayọọ nwayọọ na-agbachasị arịa ahụ na agba gbara ọchịchịrị (foto 4 na 5). Ọ bụ ngwaahịa e ji mara nke ngwakọta nke mkpụrụ ndụ ayodiin efu na ụmụ irighiri starch. Emebere iodine n'ihi oxidation nke anions iodide na anode nke cell:

(-) anode: 2I^- ? ₂ + 2e^-

Na electrode nke abụọ (cathode), ion iron (III) belatara:

(+) Katoda: 2Fe³⁺ + 2e^- ? 2 Fe²⁺

Cell redox emebere na nnwale ahụ nwere atụmatụ ndị a:

(-) C | CI_aq || FeCl_3aq | C (+)

ebe akara carbon C na-egosi electrode graphite na || ? igodo electrolytic. Mmeghachi omume n'ozuzu na sistemụ bụ oxidation nke anions I^- nke Fe cations³⁺:

2 Fe³⁺ + 2m^- ? 2 Fe²⁺ + m₂

cell redox

cell ịta ahụhụ

Maka nnwale nke abụọ ị ga-achọ: ngwọta nke ọla kọpa sulphate (II) CuSO₄, ọla kọpa electrodes, electrolytic igodo jupụtara a ndọpụ ngwọta nke potassium nitrate (V) KNO₃ na eluigwe na ala counter. Jupụta otu n'ime beaker na ngwọta CuSO.₄na onye ọzọ nwere otu dilution nke 1:100 (dịka ọmụmaatụ, 0,5 cm³ ngwọta ewepụtara site na iko mbụ, tinye mmiri na olu nke 50 cm³) (Foto nke 6). Mgbe imikpu wires ọla kọpa na iko ma mechie sekit na igodo electrolytic, tụọ voltaji n'etiti electrodes nke cell. Ọ dị obere? ihe dị ka iri na abuo ma ọ bụ ọtụtụ iri millivolts (foto 7).

Mgbasa ọla na mmeghachi omume mmiri ozuzo na-eme na electrodes:

(-) Nde: Ku⁰ ? Ya na²⁺ + 2e^- (ihe ngwọta na-enweghị uche)

(+) Cathod: Ku²⁺ + 2e^- ? Ya na⁰ (ihe ngwọta gbadoro ụkwụ karịa)

Mgbe gbakwunyere nha nke usoro electrode abụọ ahụ, ọ na-apụta na ọ dịghị mmeghachi omume kemịkal na-eme na mkpokọta! Ike ịkwọ ụgbọala nke cell bụ naanị ọchịchọ nke usoro iji mee ka mkpokọta dị na iko abụọ ahụ.