Nyob rau hauv tej rooj plaub, lub dissociation qhov tsis ua kev zoo siab?

Tshuaj yog ib tug sau ntawm atoms uas txuas mus rau txhua lwm yam los ntawm ib tug tej yam kev cai lij choj, los yog ntau tshaj precisely, txhua ntawm lawv yog ib tug system muaj nuclei thiab electrons. Yog hais tias lub system yog muaj li ntawm ib hom ntawm atoms, ces nws yuav muab hu ua ib zaug xwb-tub ntxhais, yog tias sib txawv ntawm cov atoms, cov neodnoyadernoy. Cov electrically nruab nrab system. Raws li ib tug tshwm sim ntawm sab nraud influences (kub, lub teeb, tawg los yog ncov qaumteb qabteb kuab molecules nrog dipole polarization) decays tshuaj. Cations thiab anions nyob rau hauv uas nyob rau hauv qhov kev txiav txim ntawm lub lwg me me ntawm lub ncov qaumteb qabteb hnyav (dej) molecules decompose tshuaj (ntsha) yog tsis electrically nruab nrab. Tej system nyhav equilibrium. Nyob rau hauv tsis muaj zog electrolytes piv txwv qhia tias dissociation tshua yog reversible. Rau muaj zog electrolytes, tsab ntawv no yog tsis haum, txij li thaum yuav luag tag nrho cov ntawm cov molecules dissociate rau hauv ions. Cov ntsuam ntawm lub system rau equilibrium piav los ntawm electrolytic dissociation Khao ↔ K • x + y + • A- thiab qhia tau hais tias lub dissociation qhov KD = [K +] x • [A] v / [Khao].

Los ntawm cov saum toj no kab zauv: qhov ntau undissociated molecules, tus me tus dissociation tsis tu ncua, thiab vice versa. Txawm li cas los, qhov no siv tsis tau rau muaj zog electrolytes tau pom tsis nce, tab sis txo nrog ua concentration KD. Qhov no yog vim tsis txo lub xov tooj los ntawm kev rhuav molecules thiab ua rau kom nyob nruab nrab ntawm oppositely them hais, lub kev sib nrig sib attraction quab yuam vim cov yuav txo tau nyob rau hauv kev ncua deb ntawm lawv vim lub zog concentration ntawm cov tshuaj. Yog li ntawd, muaj peev xwm ntawm muaj zog electrolytes dissociate rau hauv ions ntsuas ntsuas xws li cov khees degree ntawm dissociation, thiab cov CD tsis thov, thaum nws tsis ua kev zoo siab. Yuav kom ib tug tov ntawm ib tug tsis muaj zog ntsha muaj tsis muaj kev txiav txim zoo thov, thiab cov neeg kawm ntawv ntawm dissociation, vim hais tias nrog zuj zus lawm concentration piv ntawm dissociated molecules rau tag nrho cov xov tooj ntawm lwj yog nce, tab sis nws tsis tuab cov nyhuv uas cov ntsha. Lawv muaj peev xwm dissociate rau hauv ions qhia lub dissociation tsis tu ncua, txij thaum nws tsuas yog nyob ntawm cov tshuaj kub thiab qhov xwm ntawm tus hnyav, uas yog, KD yog ib qhov rau ib qho tshuaj yeeb dej caw Khao.

Tiaj dej (tawm ntawm tej yam ntuj tso qhov chaw, los yog ib tug uas ntws los ntawm tus kais) yog tsis huv. Ntshiab dej muaj ib tug hydronium ion [H3O + 1] thiab hydroxide ions [OH-1]. Lawv yog ua los ntawm ob tug molecules dej: H2O + H2O ↔ H3O + 1 + OH-1. Qhov no tsis tshua tshwm sim, vim hais tias cov dej yog xyaum tsis dissociate rau hauv ions, raws li ib tug tsis muaj zog ntsha. Thaum equilibrium, lub concentration ntawm hydroxide ions thiab hydronium ions yog: [H3O + 1] = [OH-1]. Tus txheej txheem yog reversible. Dej feem ntau tshwm sim raws li ib tug sib tov ntawm molecules, hydroxide ions thiab hydronium ions yeej los ntawm dej lwg me me thiab ions tam sim no nyob rau hauv tsuas muaj ib txoj lw. Qhov dissociation dej yog qhia los ntawm cov kab zauv: KD = [H3O + 1] • [OH-1] / [H2O] • [H2O ].

Acid dissociation nyob rau hauv cov tshuaj txhais tau tias cov decomposition ntawm protons H +, thiab ib tug acidic moiety. Dissociation polybasic acid nyaij nyob rau hauv ob peb kauj ruam (nyob qhov twg lub cleaved tsuas yog ib hydrogen ntawv), txhua theem yus muaj los ntawm cov nqi tsis tu ncua KD. Nyob rau hauv thawj kauj ruam hydrogen ion yog tshem tawm tau yooj yim dua tshaj nyob rau hauv tom ntej theem, yog li qhov ntawm theem rau theem decreases. Lub dissociation qhov KD yog ib qho taw qhia ntawm acid zog acid: muaj zog acids muaj ib tug ntau dua KD nqi thiab vice versa. Thaum ncav equilibrium txheej txheem lwj tus nqi thiab tus nqi ntawm molecules yog muaj sib npaug. Rau muaj zog acids tej zaum yuav siv (nrog rau cov tsuas ion-ion sis rog nyob rau hauv kev daws teeb meem ntawm muaj zog electrolytes) kev cai ntawm cov tshuaj equilibrium los xam KD ntawm 25 ° C. Rau hydrochloric acid (HCl) KD = 10000000, hydrobromic (HBr) KD = 1000000000, hydriodic (HJ) KD = 100000000000, sulfuric acid (H2SO4) KD = 1000, nitric acid (HNO3) KD = 43,6, acetate (CH3COOH) KD = 0,00002, tsianovodorodnoy (HCN) KD = 0,0000000008. Paub lub zog ntawm cov acids thiab muab piv nrog KD qhov tseem ceeb muab, nws muaj peev xwm yuav sib cav hais tias lub dissociation tsis tu ncua, ntau dua qhov lub zog acid.