CHEM 104 1st Edition Lecture 28 Svante Arrhenius 1887 definition of acids bases o Acid ionizes in aqueous solution to form H protons HA aq H aq A aq o Base ionizes in aqueous solution to form HO hydroxide o But some acids or bases for example NH 3 don t fit this definition Br nsted Lowry 1923 definition of acids bases o Acid proton donor o Base proton acceptor HA aq H2O l H30 aq A aq Molecular compounds anions cations can all be acids or bases Amines are B L bases similar to ammonia lone pair on N used to accept the proton If a compound doesn t have oxygen it isn t a B L acid Polyprotic acid can donate 2 or more protons o Also applies to bases o Ex of polyprotic acid phosphoric acid H 3PO4 Amphiprotic species functions as an acid or a base i e can donate or accept a proton o Ex is water Conjugate acid base pair pair of molecules ions that differ from each other by the presence of one proton o Ex H2S acid CO32 base HS conjugate base HCO3 conjugate acid H2O l acid H2O l base HO aq H3O aq o Ion product constant Kw HO H3O 1 10 7 M 1 10 7 M 1 10 14 at 25 C o When hydroxide concentration equals hydronium concentration solution is neutral when hydroxide conc exceeds hydronium conc solution is basic when hydronium conc exceeds hydroxide conc solution is acidic pH log H3O These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute pOH log HO pH pOH 14 In pure water at 25 C neutral pH 7 acidic pH 7 basic pH 7
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