2014_L6_AcidsandBases

3 acids bases pka log ka 9 weak acids are much

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Unformatted text preview: Ka follows the rules for equilibrium constants, it has the subscript “a” to indicate that it is the ionizaMon of an acid. CHM1321 Acids & Bases 8 STRONG ACIDS are considered to be 100% ionized in water: HNO3(aq) + H2O(l) → H3O+(aq) + NO3 ­(aq) [H3O ][NO ] Ka = >>> 1 [HNO3 ] + CHM1321 ! 3 Acids & Bases pKa = – log Ka 9 WEAK ACIDS are much less than 100% ionized in water. HOCl(aq) + H2O(l) OCl ­(aq) + H3O+(aq) [H3O ][OCl ] Ka = <<< 1 [HOCl] + CHM1321 ! Acids & Bases pKa = – log Ka 10 CHM1321 Acids & Bases 11 HA + H2O H3O+ + A ­ Strong Acid Weak Acid Ka Ka is large Ka is small pKa small or negaDve posiDve DissociaMon far to the right far to the leF Eq’m [H3O+] [H3O+] ~ [HA]o [H3O+] << [HA]o A ­ much weaker base than water A ­ much stronger base than water Strength of conjugate base CHM1321 Acids & Bases 12 Strong bases: ionize completely in water: NaOH(aq) → Na+(aq) + OH–(aq) 4 Acids & Bases At equilibrium B B Weak bases: only parMally ionize: NH3 + H2O ← NH + + OH– → CHM1321 Initially HB+ OH- B HB+ OH- 13 base acid NH3 + H2O conjugate conjugate acid base NH4+ + OH– [NH+ ][OH – ] 4 KC = [NH3 ] [NH+ ][OH – ] 4 Kb = = 1.8x10 –5 [NH3 ] This constant Kb follows the rules for equilibrium constants, it has the subscript “b” to indicate that it is the ionizaMon of a base. CHM1321 Acids & Bases 14 STRONG BASES are considered to be 100% ionized in water: NaOH(aq) → Na+(aq) + OH ­(aq) [Na ][OH ] Kb = >>> 1 [NaOH] + CHM1321 ! Acids & Bases pKb = – log Kb 15 WEAK BASES are much less than 100% ionized in water. NH3(aq) + H2O(l) OH ­(aq) + NH4+(aq) [NH ][OH ] Kb = <<< 1 [NH3 ] + 4 CHM1321 ! Acids & Bases pKb = – log Kb 16 B + H2O HB+ + OH ­ Strong Base Weak Base Kb Kb is large Kb is small pKb sma...
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This note was uploaded on 03/12/2014 for the course CHM 1321 taught by Professor Flynn during the Spring '08 term at University of Ottawa.

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