Electrochemical caij - "Inactive" zinc

Zinc yog suav tias yog ib qho khoom siv hlau. Cov txheej txheem tsis zoo qhia tau hais tias nws yuav hnov ​​​​mob hnyav nrog cov kua qaub, tshem tawm hydrogen los ntawm lawv. Tsis tas li ntawd, raws li ib qho amphoteric hlau, nws kuj reacts nrog bases los tsim cov complex ntsev. Txawm li cas los xij, zinc ntshiab yog tiv taus acids thiab alkalis. Yog vim li cas yog qhov loj repotential ntawm hydrogen evolution nyob rau saum npoo ntawm cov hlau no. Zinc impurities txhawb kev tsim cov galvanic microcells thiab, yog li ntawd, lawv dissolution.

Rau thawj qhov kev sim koj yuav xav tau: hydrochloric acid HCl, zinc phaj thiab tooj liab hlau (duab 1). Peb muab lub phaj tso rau hauv Petri tais ntim nrog dilute hydrochloric acid (duab 2), thiab muab tooj liab xaim rau nws (daim duab 3), uas HCl pom tseeb tsis cuam tshuam. Tom qab qee lub sij hawm, hydrogen yog nquag tso tawm ntawm tooj liab (duab 4 thiab 5), thiab tsuas yog ob peb lub npuas roj tuaj yeem pom ntawm zinc. Yog vim li cas yog qhov saum toj no-hais overvoltage ntawm hydrogen evolution ntawm zinc, uas yog ntau dua li ntawm tooj liab. Cov hlau sib xyaw ua ke ncav cuag tib lub peev xwm nrog kev hwm rau cov kua qaub, tab sis hydrogen yog yooj yim dua sib cais ntawm cov hlau nrog qis dua overvoltage - tooj liab. Nyob rau hauv tsim galvanic cell nrog luv Zn Cu electrodes, zinc yog cov anode:

(-) Cov Lus Qhia: Zn⁰ → zinc²⁺ + 2 e^-

thiab hydrogen raug txo rau ntawm tooj liab cathode:

(+) Lub sij hawm: 2H⁺ + 2 e^- → N₂­

Ntxiv ua ke ob qho tib si sib npaug ntawm cov txheej txheem electrode, peb tau txais cov ntaub ntawv ntawm cov tshuaj tiv thaiv zinc dissolution hauv acid:

Zinc + 2 H⁺ → zinc²⁺ + H₂­

Hauv kev sim tom ntej, peb yuav siv cov tshuaj sodium hydroxide, zinc phaj thiab cov ntsia hlau hlau (duab 6). Raws li nyob rau hauv qhov kev sim yav dhau los, zinc phaj yog muab tso rau hauv ib lub dilute NaOH tov nyob rau hauv lub Petri tais thiab ib tug ntsia thawv muab tso rau ntawm nws (hlau tsis yog amphoteric hlau thiab tsis hnov ​​​​mob nrog alkalis). Cov nyhuv ntawm qhov kev sim zoo ib yam - hydrogen tso tawm rau ntawm tus ntsia thawv, thiab cov zinc phaj tsuas yog npog nrog ob peb npuas roj (duab 7 thiab 8). Yog vim li cas rau qhov kev coj cwj pwm ntawm Zn-Fe system kuj yog qhov overvoltage ntawm hydrogen evolution ntawm zinc, uas yog ntau dua li ntawm hlau. Tsis tas li hauv qhov kev sim no, zinc yog anode:

(-) Cov Lus Qhia: Zn⁰ → zinc²⁺ + 2 e^-

thiab ntawm cov hlau cathode dej yog txo:

(+) Lub sij hawm: 2H₂O + 2e^- → N₂+ 2 UA^-

Ntxiv ob qho tib si sib npaug ntawm ob sab thiab coj mus rau hauv tus account qhov nruab nrab cov tshuaj tiv thaiv alkaline, peb tau txais cov ntaub ntawv ntawm zinc dissolution txheej txheem raws li txoj cai (tetrahydroxyincide anions yog tsim):

Zinc + 2 OH^- + 2 hli₂O → [Zn(OH)₄]^2- + H₂