Key Difference – pKa vs pKb
pKa thiab pKb yog cov ntsiab lus hauv chemistry uas hu ua dissociation constants. pKa yog acid dissociation tas li, thiab pKb yog lub hauv paus dissociation tas li. Cov ntsiab lus no yog siv los ua kom yooj yim rau kev ua haujlwm nrog cov nqi loj heev lossis me me. Cov "p" hauv cov ntsiab lus no sawv cev rau "tsis zoo logarithm". Qhov sib txawv tseem ceeb ntawm pKa thiab pKb yog pKa yog lub logarithm tsis zoo ntawm Ka thaum pKb yog lub logarithm tsis zoo ntawm Kb.
pKa yog dab tsi?
pKa is the negative logarithm of Ka. Ka yog cov kua qaub dissociation tas li ntawm kev daws. Nws yog ib qho kev ntsuas ntau ntawm lub zog ntawm cov kua qaub hauv cov kua. Cov kua qaub yog cov tshuaj sib xyaw uas tuaj yeem tso ib lossis ntau dua hydrogen ions (protons) rau kev daws. Yog tias acid dissociation tas li; Ka yog siab dua, nws txhais tau hais tias cov kua qaub yog kiag li (los yog yuav luag tag) dissociated rau hauv ions tsim hydrogen ions. Tom qab ntawd, nws qhia tau hais tias acid yog ib tug muaj zog acid. Txij li thaum pKa yog tus nqi logarithmic tsis zoo ntawm Ka, pKa yog tus nqi me dua rau cov kua qaub.
pKa=-log10Ka
Qo pKa vlaue, qhov acid zog dua. Ib yam li ntawd, tus nqi pKa ntau dua, cov kua qaub qis dua. Los ntawm saib pKa qhov tseem ceeb ntawm cov kua qaub sib txawv, ib tus tuaj yeem sib piv cov txheeb ze acid zog. Hloov chaw ntawm kev siv Ka qhov txiaj ntsig, cov txiaj ntsig pKa tau siv ntau vim nws ua kom yooj yim rau kev ua haujlwm nrog cov lej loj lossis tsawg heev nrog cov lej lej me me.
Daim duab 01: PKa qhov tseem ceeb ntawm phenol thiab nitrophenol: nitrophenol yog cov kua qaub uas muaj zog dua phenol vim nws cov nqi pKa tsawg dua piv rau nitrophenol.
Sib nrug los ntawm kev sib piv acid zog, pKa qhov tseem ceeb kuj tau siv los xaiv cov buffers tsim nyog. Raws li Henderson-Hasselbalch Equation, muaj kev sib raug zoo ntawm pH thiab pKa ntawm ib qho system.
pH=pKa + log10([A–]/[AH])
rau kev sib cais ntawm HA acid. Qhov kev sib npaug no tuaj yeem sau rov qab raws li hauv qab no.
Ka/[H+]=[A–]/[AH]
Raws li qhov sib npaug no, pKa thiab pH qhov tseem ceeb ntawm tib lub cev sib npaug thaum ib nrab ntawm cov kua qaub tau sib cais. Txij li thaum lub peev xwm buffering ntawm lub kaw lus yog nws lub peev xwm los tswj cov pH ntawm kev daws, qhov tsis yuav tsum tau xaiv nyob rau hauv uas pKa thiab pH nyob ze rau ib leeg.
pKb yog dab tsi?
pKb yog qhov tsis zoo logarithm ntawm Kb. Kb yog lub hauv paus dissociation tas li. Nws yog siv los txiav txim siab lub zog ntawm lub hauv paus quantitatively. Thaum lub hauv paus yog yaj hauv dej, nws dissociates rau hauv ions tsim ib qho kev daws teeb meem. Lub hauv paus muaj zog dissociate kiag li. Cov hauv paus tsis muaj zog cuam tshuam ib nrab.
pKb=-log10Kb
Tus "p" hauv pKb sawv rau "tsis zoo logarithm". Txij li feem ntau ntawm cov txiaj ntsig Kb yog qhov loj heev lossis me me, qhov tsis zoo logarithms ntawm cov txiaj ntsig no tau siv los ua kom yooj yim rau kev daws teeb meem. Yog li ntawd, tus nqi Kb loj tuaj yeem ua tus yam ntxwv los ntawm tus nqi pKb me me nrog cov lej lej me me.
Kev sib raug zoo ntawm pKa thiab pKb yog dab tsi?
Kev sib raug zoo ntawm Ka thiab Kb yog muab raws li hauv qab no.
Kw=Ka. Kb
Cia li kev sib raug zoo ntawm pKa thiab pKb yog muab raws li, (ntawm 25oC)
pKa + pKb=14
pKa thiab pKb txawv li cas?
pKa vs pKb |
|
| pKa is the negative logarithm of Ka. | pKb is the negative logarithm of Kb. |
| Nature | |
| pKa muab rau cov kua qaub. | pKb yog muab rau hauv paus. |
| Kev sib raug zoo nrog kev sib cais tsis tu ncua | |
| pKa is related to acid dissociation constant. | pKb cuam tshuam nrog lub hauv paus dissociation tas li. |
| Indications | |
| Me me tus nqi pKa, muaj zog dua cov kua qaub. | Me me tus nqi pKb, qis dua lub hauv paus. |
Summary – pKa vs pKb
pKa thiab pKb yog siv los sib piv lub zog ntawm cov kua qaub thiab cov hauv paus raws. pKa yog muab rau cov kua qaub dissociation. pKb yog muab rau dissociation ntawm lub hauv paus. Qhov sib txawv ntawm pKa thiab pKb yog pKa yog qhov tsis zoo logarithm ntawm Ka whereas pKb yog lub logarithm tsis zoo ntawm Kb.
Download the PDF of pKa vs pKb
Koj tuaj yeem rub tawm PDF version ntawm kab lus no thiab siv nws rau offline hom phiaj raws li daim ntawv ceeb toom. Thov download PDF version ntawm no: Qhov txawv ntawm pKa thiab pKb
