CH301 - Type1.conjBASE

CH301 - Type1.conjBASE - TYPE 1 (conj. BASE of weak acid) (...

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TYPE 1 (conj. BASE of weak acid) ( only the SALT of a weak acid put in solution ) For a salt of a weak acid (NaA) in water: STEP 1: NaA (s) + H 2 O Na + + A - (100% ionization!!!) STEP 2: A - + H 2 O HA + OH - Note that A - behaves EXACTLY like a weak base in water (a Type 1 problem for bases) and the equilibria is K b - OH HA A = - [] [ ] and remember K b for A - must be calculated from K a for HA: K K K b w a = Now let C A- be the analytical concentration (label) of the conjugate base, A - : Our Equilibrium "Chart" [A - ] [OH - ] [HA] initial C A- 00 change -x +x +x final C A- - xx x K x x b 2 A C - = - (29 Equation 3.1 KC K x x b A b - -= () 2 0 2 =+ - xK bb A C - [ ] OH A 4C bbb A - -- == = -+ + x KKK 2 2 This equation is the exact solution for calculating the [OH - ] for any solution made by mixing a concentration of
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