1. Teb ua ntej: phosphoric acid tsis yog "muaj zog heev" acid-nws yog nruab nrab-lub zog acid
Phosphoric acid(H₃PO₄) tsis yog "muaj zog heev" acid. Hauv kev faib tshuaj chemical nws yog anruab nrab -lub zog acid(ib qho triprotic acid): nws muaj zog ntau dua li cov acids uas tsis muaj zog xws li carbonic acid thiab acetic acid, tab sis kom meej meej tsis muaj zog dua li cov acids muaj zog xws li hydrochloric, sulfuric thiab nitric acid. Cov lus "phosphoric acid yog cov kua qaub uas muaj zog heev" yog li tsis raug thiab yuav tsum tsis lees paub.
2. Yog vim li cas phosphoric acid tsis yog ib tug muaj zog acid
Cov kua qaub muaj zog yog txhais los ntawm kev sib cais ua tiav hauv dej; phosphoric acid dissociates ib feem.
Cov kua qaub muaj zog yog ib qho uas dissociates tag nrho (los yog yuav luag tag) rau hauv hydrogen ions hauv cov kua dej, xws li hydrochloric acid, nitric acid, thiab sulfuric acid (nws thawj kauj ruam dissociates kiag li). Phosphoric acid yog ib tug triprotic acid uas dissociates nyob rau hauv peb reversible kauj ruam; ib tug loj feem ntawm undissociated H₃PO₄ molecules tseem nyob rau hauv kev daws, yog li nws tsis ua raws li "tag nrho dissociation" cov txheej txheem.
Nws cov dissociation tsis tu ncua qhia txwv ionization.
Peb theem kev sib cais ntawm phosphoric acid yog pKa1 ≈ 2.15, pKa2 ≈ 7.20 thiab pKa3 ≈ 12.35. Pom tau tias muaj zog acids feem ntau muaj qhov tsis zoo pKa (piv txwv li hydrochloric acid yog li −7). Phosphoric acid thawj -qib pKa yog qhov zoo thiab nyob deb ntawm xoom, qhia txog kev txwv ionization; cov kauj ruam thib ob thiab thib peb tseem tsis muaj zog, thiab qhov thib peb (pKa3 ≈ 12.35) yog qhov tsis txaus ntseeg.
Kev sib piv nrog cov kua qaub muaj zog pom tau tias muaj qhov sib txawv.
Hydrochloric, nitric, sulfuric (thawj kauj ruam) thiab perchloric acid dissociate yuav luag tag rau hauv dej thiab muaj ntau acidic tshaj phosphoric acid. Ntawm txhua qhov concentration, phosphoric acid tsis tuaj yeem ncav cuag lawv qib ntawm ionization, yog li nws tsis tuaj yeem pom "muaj zog" acidity.
Nws ua tsis tau qhov kev txhais -raws li kev xeem.
Cov txheej txheem rau lub zog acid yog tiav dissociation. Phosphoric acid tsis ua raws li cov txheej txheem no thiab, los ntawm cov ntsiab lus tshuaj, tsis tuaj yeem muab cais ua cov kua qaub muaj zog; nws yog nyob rau hauv nruab nrab - qeb zog.
3. Yog vim li cas phosphoric acid tsis muaj zog acid
Nws thawj - kauj ruam dissociation yog kom meej meej siab tshaj qhov uas tsis muaj zog acids.
Phosphoric acid muaj pKa1 ≈ 2.15, zoo hauv qab ntawm acetic acid (pKa ≈ 4.76) thiab carbonic acid (pKa1 ≈ 6.35). Qhov me me pKa, qhov muaj zog ntawm cov kua qaub; thawj -qib ionization ntawm phosphoric acid yog li deb tshaj li ntawm cov tsis muaj zog acids.
Nyob rau tib lub concentration nws yog kom meej meej ntau acidic.
Hauv 0.1 mol / L aqueous tov, phosphoric acid muab pH ntawm kwv yees li 1.6, whereas acetic acid ntawm tib lub concentration muab txog 2.9- hydrogen-ion concentration ntawm phosphoric acid yog kwv yees li 20 npaug ntau dua.
Nws reactivity thiab industrial siv qhia txog nruab nrab -lub zog acidity.
Phosphoric acid reacts nrog hlau oxides, hydroxides thiab carbonates los tsim phosphates, thiab yog dav siv nyob rau hauv phosphating, etching, pickling thiab pH hloov. Nyob rau hauv cov ntaub ntawv no nws acidity yog exploited mus rau ib tug℃uas ib txwm tsis muaj zog acids xws li acetic thiab carbonic acid tsis tuaj yeem muab, uas qhia tau hais tias nws lub zog tsis yog "tsis muaj zog".
Nws ua tsis tau qhov kev txhais -raws li kev xeem.
Lub acidity ntawm phosphoric acid nyob nruab nrab ntawm cov acids uas muaj zog thiab tsis muaj zog: nws tsis ncav cuag "tag nrho dissociation" tus qauv ntawm cov acids muaj zog, tab sis nws muaj zog dua li cov acids tsis muaj zog. Hu nws cov kua qaub tsis muaj zog yog li ntawd kuj tsis raug; classifying nws li anruab nrab -lub zog acidqhia txog qhov tseeb.
