Lub degree ntawm dissociation ntawm tsis muaj zog thiab muaj zog electrolytes

Lub sij hawm "dissociation" nyob rau hauv Chemistry thiab Biochemistry kev lwj yog txoj kev tshuaj mus rau hauv ions thiab radicals. Dissociation - yog qhov opposite phenomenon ntawm lub koom haum los yog recombination, thiab nws yog reversible. Ntau kwv yees ntawm lub dissociation yog ua los ntawm xws li ib tug nqi raws li cov neeg kawm ntawv ntawm dissociation. Nws muaj ib tsab ntawv los α thiab characterizes ib dissociation cov tshuaj tiv thaiv nyob rau hauv ib tug uniform (homogeneous) systems raws li cov kab zauv: CA ↔ R + A xeev ntawm equilibrium. SC - ib tug particle ntawm lub pib khoom, K thiab A - yog zoo hais uas tsoo raws li ib tug tshwm sim ntawm dissociation ntawm loj particulate khoom. Los ntawm uas nws hais ntxiv hais tias lub system yuav dissociated thiab undissociated hais. Yog hais tias peb xav hais tias cov n molecules disintegrated thiab tsis disintegrated N molecules, cov qhov tseem ceeb yuav siv tau los yamntxwv lub dissociation, uas yog xam raws li ib feem pua: α = n • 100 / N los yog chav tsev fractions: α = n / N.

Hais tias yog, cov neeg kawm ntawv ntawm dissociation yog tus piv ntawm dissociated hais (molecules) homogeneous system (tshuaj) thawj zaug nqi hais (molecules) nyob rau hauv lub system (tshuaj). Yog hais tias nws yog lub npe hu hais tias α = 5%, nws txhais tau tias tsuas 5 tawm ntawm 100 molecules ntawm thawj zaug molecules yog nyob rau hauv daim ntawv ntawm ions, thiab tshuav 95 molecules tsis decompose. Rau txhua tus neeg tshuaj α yuav, raws li nws yog nyob rau hauv lub tshuaj xwm ntawm lub molecule, thiab tseem nyob rau hauv lub kub thiab nyob rau tus nqi ntawm cov tshuaj nyob rau hauv ib tug homogeneous system (tshuaj), i.e. rau nws concentration. Muaj zog electrolytes, uas muaj xws li tej yam acids, bases thiab ntsev nyob rau hauv cov tshuaj kiag li dissociate rau hauv ions, rau qhov no yog vim li cas yog tsis haum rau kev kawm dissociation txheej txheem. Yog li ntawd, rau txoj kev tshawb no ntawm thov tsis muaj zog electrolytes, lub lwg me me dissociate rau hauv ions nyob rau hauv lub tshuaj yog tsis tau kiag li.

Rau reversible tshua dissociation dissociation qhov (KD), uas characterizes lub xeev ntawm equilibrium, yog txiav txim los ntawm cov mis: KD = [K] [A] / [CA]. Yuav ua li cas cov neeg kawm ntawv ntawm lub dissociation qhov thiab sib thooj,, nws yog ua tau yuav tau xav txog cov piv txwv ntawm ib tug tsis muaj zog ntsha. Raws li cov kev cai lij choj ntawm dilution ua tag nrho cov zajlus kom txoj kev xav: KD = c • α2, qhov twg c - concentration ntawm cov tshuaj (nyob rau hauv cov ntaub ntawv no ib tug = [SC]). Nws yog lub npe hu hais tias nyob rau hauv cov kua ntim V 1 mol dm3 yaj substance. Nyob rau hauv lub xeev pib lub concentration ntawm cov pib cov ntaub ntawv uas molecules yuav qhia los ntawm: c = [SC] = 1 / V mol / dm3, thiab cov ion concentration yuav tsum: [R] = [A] = 0 / V mol / dm3. Thaum ncav equilibrium lawv qhov tseem ceeb yog hloov: [kos] = (1 - α) / V mol / dm3 thiab [R] = [A] = α / V mol / dm3, whereas KD = (α / V • α / V) / (1 - α) / V = α2 / (1 - α) • V. Cov ntaub ntawv ntawm me ntsis dissociating electrolytes, lub dissociation degree (α) uas yog nyob ze rau zero, thiab qhov ntim ntawm cov tshuaj yuav tsum qhia tias nyob rau hauv cov nqe lus ntawm lub npe hu concentration: V = 1 / [SV] = 1 / s. Ces tus kab zauv yuav hloov: KD = α2 / (1 - α) • V = α2 / (1 - 0) • (1 / s) = α2 • s, thiab extracting lub square hauv paus ntawm qhov feem KD / s, nws yog ua tau los mus laij lub degree ntawm dissociation ntawm α. Qhov no txoj cai yog siv tau yog tias α yog npaum li cas me dua 1.

Rau muaj zog electrolytes muaj ntau tsim nyog lub sij hawm yog lub khees degree ntawm dissociation. Nws yog pom raws li tus piv ntawm cov khees nqi ntawm dissociated particle mus rau ib tug tiag tiag los yog txhais ntawm mis isotonic coefficient (hu ua lub van't Hoff tau, thiab qhia tau hais tias lub yeej muaj tseeb tus cwj pwm ntawm ib yam khoom nyob rau hauv cov tshuaj): α = (i - 1) / (n - 1). Ntawm no kuv - Van't Hoff tau, thiab n - nqi ntawm ua ions. Ntsiab, lub lwg me me kiag li disintegrated mus rau hauv ions, α ≈ 1, thiab nrog zuj zus lawm ntau ntawm α nce nyhav 1. Tag nrho cov no yog piav qhia los lub hom phiaj ntawm muaj zog electrolytes, uas asserts uas lub zog ntawm cations thiab anions cuam tshuam muaj zog ntsha molecules yog ib qhov nyuaj rau ob peb yog vim li cas. Ua ntej, ions yog surrounded los ntawm molecules ntawm lub ncov qaumteb qabteb hnyav, nws yog ib lub electrostatic sis yog hu ua solvation. Ob, oppositely them cations thiab anions nyob rau hauv cov tshuaj, vim qhov kev txiav txim ntawm kev sib nrig sib attraction rog daim ntawv associates los yog ion officers. Associates coj raws li undissociated molecules.