Qhov txawv ntawm pH thiab pKa

2024 Tus sau: Alex Aldridge | [email protected]. Kawg hloov kho: 2023-12-17 13:40

pH vs pKa

Peb ib txwm txheeb xyuas cov kua qaub ua tus pub dawb proton. Acids muaj qaub saj. Txiv qaub kua txiv, vinegar yog ob tug acids peb tuaj nyob rau hauv peb lub tsev. Lawv hnov mob nrog cov hauv paus ua dej, thiab ua rau cov hlau ua H_{2; yog li, nce hlau corrosion tus nqi. Lub peev xwm los pub cov proton yog cov yam ntxwv ntawm cov kua qaub, thiab pH, PKa qhov tseem ceeb yog xam raws li tus yam ntxwv no.}

pH

pH yog qhov ntsuas uas siv tau los ntsuas cov kua qaub lossis qhov pib hauv cov tshuaj. Qhov ntsuas muaj tus lej ntawm 1 txog 14. pH 7 yog suav tias yog tus nqi nruab nrab. Cov dej ntshiab tau hais tias muaj pH 7. Hauv pH nplai, los ntawm 1-6 acids yog sawv cev. Cov kua qaub tuaj yeem muab faib ua ob, raws li lawv lub peev xwm los sib cais thiab tsim cov protons. Cov kua qaub muaj zog zoo li HCl, HNO ₃ yog ionized tag nrho hauv cov tshuaj kom muab cov protons. Cov acids tsis muaj zog xws li CH_{3COOH ib nrab dissociate thiab muab tsawg dua ntawm cov protons. Cov kua qaub nrog pH 1 tau hais tias muaj zog heev, thiab raws li tus nqi pH nce, acidity txo. Yog li ntawd, pH qhov tseem ceeb tshaj 7 qhia qhov tseem ceeb. Raws li qhov pib nce, pH tus nqi kuj yuav nce ntxiv thiab cov hauv paus muaj zog yuav muaj pH tus nqi 14.}

pH nplai yog logarithmic. Nws tuaj yeem sau tau raws li hauv qab no hauv cov txheeb ze rau H^{+ concentration hauv cov tshuaj.}

pH=-log [H^+]

Nyob hauv qhov kev daws teeb meem, tsis muaj H⁺s. Yog li ntawd, nyob rau hauv ib qho xwm txheej zoo li ntawd, pOH tuaj yeem txiav txim siab los ntawm –log [OH^{–] tus nqi.}

Vim, pH + pOH=14; pH tus nqi ntawm ib qho kev daws teeb meem tseem tuaj yeem xam. Muaj cov pH ntsuas thiab pH cov ntaub ntawv hauv chav kuaj, uas tuaj yeem siv los ntsuas pH qhov tseem ceeb ncaj qha. pH cov ntaub ntawv yuav muab kwv yees pH qhov tseem ceeb, qhov pH meters muab qhov tseeb dua.

pKa

Acidity yog lub xeev ntawm kev ua kua qaub. Qhov no muaj feem xyuam rau qhov degree ntawm kev ua acid. Cov kua qaub tuaj yeem muab faib ua ob, raws li lawv lub peev xwm los sib cais thiab tsim cov protons. Cov acids muaj zog xws li HCl, HNO ₃ yog ionized tag nrho hauv cov tshuaj, muab cov protons. Cov acids tsis muaj zog xws li CH₃COOH ib nrab dissociate thiab muab tsawg dua ntawm cov protons. K_{a yog cov kua qaub dissociation tas mus li. Nws muab ib qho kev qhia txog lub peev xwm ntawm cov tsis muaj zog acid, kom poob ib tug proton. Hauv qhov nruab nrab aqueous, cov kua qaub tsis muaj zog nyob hauv qhov sib npaug nrog nws lub hauv paus conjugate raws li qhia hauv qhov piv txwv hauv qab no.}

CH₃COOH_(aq) + H₂O _(l) CH₃COO^–_(aq) + H 3_O(aq)

Txoj kev sib npaug ntawm cov saum toj no tuaj yeem sau ua, E=[CH3COO-] [H3O+] / [CH3COOH] [H2O]

Qhov kev sib npaug no tuaj yeem sau rov qab tau raws li hauv qab no hloov pauv qhov tsis tu ncua rau acid dissociation tas li.

Ka=[CH3COO–] [H3O+] / [CH3COOH]

Qhov sib txuam ntawm tus nqi logarithm ntawm Ka yog tus nqi pKa. Nov yog lwm txoj hauv kev qhia txog acidity.

pKa=-log K_a

Rau cov kua qaub uas muaj zog dua, Ka tus nqi loj dua, thiab tus nqi pKa tsawg dua. Thiab rau qhov tsis muaj zog acid, nws yog qhov ntxeev.

pH thiab pKa yog dab tsi?

• pH yog qhov sib npaug ntawm logarithm ntawm H^{+ concentration. pKa yog lub logarithm ntawm Ka tus nqi.}

• pH muab tswv yim txog tus nqi ntawm H^{+ ions tam sim no hauv nruab nrab. pKa tus nqi muab ib lub tswv yim hais txog rau sab twg qhov sib npaug yog nyiam (lub degree ntawm acid dissociation).}

• Ob leeg pH thiab pKa cuam tshuam los ntawm Henderson-Hasselbalch equation: pH=pKa + log ([A^–]/[HA])