CH301 - pHcurvebase

CH301 - pHcurvebase - Titration Curve weak base with strong...

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mL of acid added pH buffer zone a “type 2” calculation The START of the titration is the same as a regular (type 1) weak base problem. You know K b and [B] so you can calculate pH. B + H 2 O BH + + OH - The equivalence point (endpoint) is the same as a regular (type 1) salt of a weak base problem (BHX). You know [BH + ] and you can calculate pH. Also note that the pH must be less than 7 due to the ionization of BH + . BH + B + H + This region is calculated simply by determining the amount of overshoot pH = 7.00 pH = 7.00 conjugate ratios are known, use Henderson-Hasselbach to calculate pH. pH’s are generally above 7 here.
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Unformatted text preview: Titration Curve weak base with strong acid McCord © 2002 pH = p K a endpoint (complete titration) half titration The half-way point is important! After you have determined the equivalence point (endpoint) of the titration, go to half that value. The pH at the half-titration point is equal to the p K a of the weak acid, BH + . To get the p K b of the base (B) you MUST subtract the p K a from 14. The reason for this is that the pOH is actually what equals the p K b. p K b = 14 - p K a H + in EXCESS that has been added. No equilibrium calculations necessary. for BH + !...
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