Acids thiab alkalis yog ob txoj haujlwm hnyav ntawm tib qhov teev: lawv cov khoom (tshwj tsis yog kiag li) raug txiav txim los ntawm tib tus nqi - qhov concentration ntawm hydrogen ions (H+). Txawm li cas los xij, nyob rau hauv nws tus kheej tus lej no tsis yooj yim heev: txawm tias nyob rau hauv ib puag ncig acidic, qhov twg cov concentration ntawm hydrogen ions siab dua, tus lej no yog pua pua, txhiab ntawm ib chav. Yog li ntawd, kom yooj yim, lawv siv tus lej logarithm ntawm tus nqi no, muab faib los ntawm tus lej rho tawm. Nws yog kev cai hais tias qhov no yog pH (potentia Hydrogen), los yog qhov taw qhia hydrogen.
Kev tshwm sim ntawm lub tswvyim
Feem ntau, qhov tseeb tias ib puag ncig acidic thiab alkaline ib puag ncig yog txiav txim siab los ntawm cov concentration ntawm hydrogen ions H + thiab tias lawv cov concentration ntau dua, cov kua qaub ntau dua (thiab lwm yam, qhov qis dua H + concentration, ntau alkaline ib puag ncig thiab siab dua qhov concentration ntawm opposite OH ions -), tau paub txog science rau lub sij hawm ntev. Txawm li cas los xij, nws tsis yog txog xyoo 1909 uas Danish chemist Sørensen thawj zaug luam tawm kev tshawb fawb uas nws siv lub tswv yim ntawm hydrogen index - PH, tom qab hloov los ntawm pH.
Xaiv acidity
Thaum xam cov pH Performance index, nws yog assumed tias dej molecules nyob rau hauv kev daws, txawm hais tias nyob rau hauv tsawg heev, tseem dissociate rau ions. Cov tshuaj tiv thaiv no hu ua dej autoprotolysis:
H2O H+ + OH-
Cov tshuaj tiv thaiv yog thim rov qab, yog li qhov sib npaug tas li tau txhais rau nws (qhia qhov nruab nrab ntawm txhua qhov sib xyaw). Ntawm no yog tus nqi ntawm qhov tsis tu ncua rau cov txheej txheem - kub 22 ° C.
Kub hauv qab hauv kab ntawv square - molar concentrations ntawm cov khoom qhia. Cov molar concentration ntawm cov dej hauv dej yog kwv yees li 55 mol / liter, uas yog tus nqi thib ob. Yog li ntawd, cov khoom ntawm cov concentrations ntawm H+ thiab OH- ions yog hais txog 10-14. Tus nqi no hu ua ionic khoom ntawm dej.
Hauv dej ntshiab, qhov concentration ntawm hydrogen ions thiab hydroxide ions yog 10-7. Raws li, tus nqi pH ntawm cov dej yuav yog kwv yees li 7. Tus nqi pH no raug coj los ua ib qho chaw nruab nrab.
Tom ntej no, koj yuav tsum tau saib deb ntawm dej thiab xav txog kev daws ntawm qee cov kua qaub lossis alkali. Piv txwv li, noj acetic acid. Cov khoom ionic ntawm cov dej yuav nyob zoo ib yam, tab sis qhov sib npaug ntawm cov ions H+ thiab OH- yuav hloov mus rau yav dhau los: hydrogen ions yuav los ntawm ib nrab dissociated acetic acid, thiab "ntxiv" hydroxide ions yuav nkag mus rau hauv cov dej uas tsis yog-dissociated molecules. Yog li, qhov concentration ntawm hydrogen ions yuav siab dua thiab pH yuav qis dua (tsis xav tautsis nco qab tias lub logarithm raug coj nrog lub cim rho tawm). Yog li, acidic thiab alkaline muaj feem xyuam rau pH. Thiab lawv txuas nrog hauv txoj kev hauv qab no. Tus nqi pH qis dua, qhov acidic ntau dua ib puag ncig.
Acidic Properties
Acidic ib puag ncig yog cov kev daws teeb meem nrog pH tsawg dua 7. Nws yuav tsum tau muab sau tseg tias txawm hais tias tus nqi ntawm cov khoom ionic ntawm dej thaum xub thawj pom txwv qhov pH qhov tseem ceeb ntawm 1 txog 14, Qhov tseeb, kev daws teeb meem nrog pH tsawg dua ib qho (thiab txawm tias tsawg dua xoom) thiab ntau dua 14 muaj nyob. Piv txwv li, nyob rau hauv cov ntsiab lus daws teeb meem ntawm cov acids muaj zog (sulfuric, hydrochloric) pH tuaj yeem ncav cuag -2.
Lub solubility ntawm tej yam khoom yuav nyob ntawm seb peb puas muaj acidic ib puag ncig los yog alkaline ib puag ncig. Piv txwv li, siv cov hlau hydroxides. Solubility yog txiav txim los ntawm tus nqi ntawm cov khoom solubility, uas yog tib yam nyob rau hauv cov qauv raws li cov khoom ion ntawm dej: multiplied concentrations. Nyob rau hauv cov ntaub ntawv ntawm hydroxide, cov khoom solubility muaj xws li cov concentration ntawm cov hlau ion thiab cov concentration ntawm hydroxide ions. Nyob rau hauv cov ntaub ntawv ntawm ib tug ntau tshaj ntawm hydrogen ions (nyob rau hauv ib tug acidic ib puag ncig), lawv yuav nquag "rub tawm" hydroxide ions los ntawm precipitate, yog li hloov qhov sib npaug ntawm daim ntawv yaj, ua rau kom cov solubility ntawm precipitate.
Nws tseem tsim nyog hais tias tag nrho tib neeg txoj hnyuv muaj ib puag ncig acidic: pH ntawm cov kua txiv hmab txiv ntoo nyob ntawm 1 txog 2. Kev sib txawv ntawm cov txiaj ntsig no nce lossis nqis tuaj yeem ua rau muaj ntau yam kab mob.
Cov khoom ntawm alkaline nruab nrab
BNyob rau hauv ib qho chaw alkaline, tus nqi pH yuav siv sij hawm qhov tseem ceeb tshaj 7. Rau kev yooj yim, nyob rau hauv ib puag ncig uas muaj siab concentration ntawm hydroxide ions, pH qhia txog acidity yog hloov los ntawm pH qhia pOH pH. Nws yog ib qho yooj yim los twv tias nws qhia tus nqi sib npaug rau -lg[OH-] (tsis zoo lej lej logarithm ntawm qhov concentration ntawm hydroxide ions). Ncaj nraim los ntawm cov khoom ionic ntawm dej ua raws qhov sib npaug pH + pOH=14. Yog li pOH=14 - pH. Yog li, rau tag nrho cov nqe lus uas muaj tseeb rau pH Performance index, cov lus rov qab yog qhov tseeb rau pOH qhov ntsuas qhov tseem ceeb. Yog tias pH ntawm alkaline nruab nrab yog qhov loj los ntawm kev txhais, ces nws cov pOH yog qhov tseeb me me, thiab qhov muaj zog ntawm cov tshuaj alkali, qhov pOH nqi qis dua.
kab lus no nyuam qhuav qhia txog qhov tsis sib haum xeeb uas cuam tshuam ntau qhov kev sib tham txog acidity: qis acidity qhia tias acidity siab, thiab vice versa: siab pH tus nqi sib haum mus rau qis acidity. Qhov no paradox tshwm vim hais tias lub logarithm yog coj nrog ib tug rho tawm kos npe rau, thiab lub acidity scale yog, raws li nws yog, inverted.
Tswv yim txhais ntawm acidity
Cov ntsuas ntsuas yog siv los txiav txim siab acidity ntawm nruab nrab. Feem ntau cov no yog cov organic molecules nyuaj uas hloov lawv cov xim nyob ntawm pH ntawm nruab nrab. Qhov taw qhia hloov xim dhau qhov nqaim pH ntau yam: qhov no yog siv hauv cov kua qaub-puag titrations kom ua tiav cov txiaj ntsig raug: qhov titration nres sai li sai tau thaum qhov ntsuas hloov xim.
Cov ntsuas nto moo tshaj plaws yog methyltxiv kab ntxwv (hloov ncua sij hawm nyob rau hauv cheeb tsam nrog ib tug tsawg pH), phenolphthalein (hloov ncua sij hawm nyob rau hauv lub cheeb tsam nrog ib tug siab pH), litmus, thymol xiav thiab lwm yam. Nyob rau hauv ib puag ncig acidic thiab alkaline ib puag ncig, cov ntsuas sib txawv yog siv nyob ntawm thaj chaw uas lawv qhov kev hloov pauv hloov pauv.
Tseem muaj cov cim qhia thoob ntiaj teb - lawv hloov lawv cov xim maj mam los ntawm liab mus rau ntshav liab thaum tsiv los ntawm cov kua qaub rau cov alkaline ib puag ncig. Qhov tseeb, universal indicators are a mix of common ones.
Rau qhov kev txiav txim siab ntau dua ntawm cov kua qaub, cov cuab yeej siv - pH meter (potentiometer, txoj kev, feem, hu ua potentiometry). Nws lub hauv paus ntsiab lus ntawm kev ua haujlwm yog ua raws li kev ntsuas ntawm EMF hauv ib lub voj voog, lub ntsiab ntawm cov tshuaj uas ntsuas pH. Lub peev xwm ntawm ib qho electrode raus hauv ib qho kev daws yog rhiab rau qhov concentration ntawm hydrogen ions hauv cov tshuaj - yog li qhov kev hloov hauv EMF, raws li qhov pH tiag tiag yog xam.
Acidity ntawm ntau qhov chaw hauv lub neej txhua hnub
Qhov ntsuas acidity yog qhov tseem ceeb hauv lub neej txhua hnub. Piv txwv li, tsis muaj zog acids - acetic, malic - yog siv los ua preservatives. Cov tshuaj alkaline yog cov tshuaj ntxuav tes, suav nrog xab npum. Cov xab npum yooj yim tshaj plaws yog sodium ntsev ntawm fatty acids. Nyob rau hauv dej, lawv dissociate: cov fatty acid residue - ntev heev - ntawm ib sab tes muaj ib tug tsis zoo nqi, thiab nyob rau lwm yam - ib tug ntev tsis-polar saw ntawm carbon atoms. Qhov ntawdqhov kawg ntawm cov molecule, uas tus nqi koom nrog hydration, sau cov dej molecules nyob ib ncig ntawm nws. Lwm qhov kawg txuas rau lwm yam uas tsis yog-polar, zoo li cov roj molecules. Yog li ntawd, micelles tau tsim - cov pob, uas "tails" nrog cov nqi tsis zoo tawm, thiab "tails" thiab cov khoom ntawm cov rog thiab av tau muab zais rau hauv. Qhov saum npoo yog ntxuav los ntawm roj thiab av vim qhov tseeb tias cov tshuaj ntxuav tes khi tag nrho cov roj thiab cov av rau hauv cov micelles.
Acidity thiab noj qab haus huv
Nws twb tau hais tias pH tseem ceeb heev rau tib neeg lub cev. Ntxiv nrog rau txoj hnyuv, nws yog ib qho tseem ceeb uas yuav tsum tswj cov acidity Performance index nyob rau hauv lwm qhov chaw ntawm lub cev: ntshav, qaub ncaug, tawv nqaij - acidic thiab alkaline ib puag ncig yog ib qho tseem ceeb heev rau ntau yam kab mob lom. Lawv lub ntsiab lus tso cai rau koj los ntsuas lub xeev ntawm lub cev.
Tam sim no kev ntsuas pH tau txais kev muaj koob npe - qhov kev xeem hu ua kev kuaj xyuas cov kua qaub. Lawv yog ib txwm strips ntawm daim ntawv qhia universal.
