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Unformatted text preview: Lecture 18 (TC) Nov. 6, 2008 Notes Arrhenius Acids/Bases: ‐ Arrhenius Acids have a removable H+. ‐ Arrhenius Bases have a removable OH‐. ‐ Arrhenius acid‐base RXNs have the format/model: 1) Acid + Base →← Salt + Water > HA + B(OH) →← (B+)(A‐) + H2O 2) HA →← H+ + A‐ B(OH) →← B+ + OH‐ = HA + B(OH) →← H+ + A‐ + B+ + OH‐ Bronsted‐Lowry Acids/Bases: ‐ Bronsted‐Lowry Acids have removable H+. ‐ Bronsted‐Lowry Bases can ‘accept’ H+ from an acid (acid 1 or acid 2). ‐ Removing H+ causes the corresponding base to be more ‘negative’ charge. ‐ Conjugates: Related by H+. ‐ Bronsted‐Lowry Acid/Base RXNs usually have the format: 1) Acid 1 →← H+ + Base 1 Base 2 + H+ →← Acid 2 = Acid 1 + Base 2 + H+ →← H+ + Acid 2 + Base 1 > ‘H+’ gets crossed out on both sides (like intermediates). = Acid 1 + Base 2 →← Acid 2 + Base 1 (or) = HA + B →← HB+ + A‐ Arrhenius: ‐ Arrhenius Acids produce H+ when added to water ((l) H2O). ‐ Arrhenius Bases produce OH‐ when added to water ((l) H2O). Bronsted‐Lowry: ‐ Bronsted‐Lowry Acids donate protons (H+). ‐ Bronsted‐Lowry Bases accept protons (H+). Amphiprotic Substances: ‐ Some chemicals can be an acid or a base. ‐ Water is an Amphiprotic Substance. ‐ Water can be both a proton donator as well as a proton acceptor. ‐ Autoionization: a fast equilibrium rxn that is always occurring whenever there is water present. Using the table of Conjugate Acid‐Base Pairs: ‐ The acids column is in order from Large to Lowest Ka. (Top to bottom order). ‐ The Base column is in order from weakest to strongest. (Top to bottom order). ‐ The stronger the acid, the weaker the base. ‐ The weaker the acid, the stronger the base. Conjugate: ‐ Conjugate acids/bases differ by a H+. Acid Ionization constant: K a ‐ Acid ionization constant = ‐ This is a measure of ACID STRENGTH. ‐ If Ka is larger, the Acid is stronger. If its smaller, the Acid is weaker. ...
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- Fall '08