patino_chm2046_chapter16

100 m naoh to the equivalence point 0100 m naoh to

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Unformatted text preview: lt; 7 WA-WB, pH ? Solution of known concn added to another Titrant volume, mL Titrant volume, mL QUESTION: Titrate 100. mL of a 0.025 M QUESTION: Titrate 100. mL of a 0.025 M QUESTION: solution of benzoic acid ((Ka= 6.25E-5)) with solution of benzoic acid Ka = 6.25E-5 with solution with solution with 0.100 M NaOH to the equivalence point. 0.100 M NaOH to the equivalence point. 0.100 0.100 pH at pH at pH pH half-way half-way point? point? point? point? Benzoic acid Benzoic acid + NaOH + NaOH pH after pH end pt!! pH at pH at pH pH equivalence equivalence point? point? point? point? pH of solution of pH of solution of pH pH benzoic acid, a benzoic acid, a weak acid? weak acid? weak weak Acid­Base Titration Acid­Base Titration Q: Titrate 100. mL of a 0.025 M solution of benzoic acid with 0.100 M NaOH to the equivalence point. What is the pH of the solution at the equivalence point? Ka of HBz = 6.25x10−5 Ka HBz + NaOH → Na+ + Bz- + H2O HBz + OH− → Bz- + H2O K=1/Kb of BzHBz OH This reactions happens until completion; K>>1 (see next) C6H5CO2H = HBz Benzoate ion = Bz- Acid­Base Titration Acid­Base Titration Q: Titrate 100. mL of a 0.025 M solution of benzoic acid with 0.100 M NaOH to the equivalence point. the What is the pH of the final solution? At this point, VNaOH = 25 mL Mac Vac = Mbase Vbase At Ka =6.25E-5 HBz + OH− → Bz− + H2O K=1/Kb = ————— ————— Kw = 1E-14 K = 6.25 x 109 too large! Complete reaction! 6.25 Complete The pH of the final solution will be 1. Less than 7 2. Equal to 7 3. Greater than 7 Acid­Base Titrations Acid­Base Titrations The product of the titration of benzoic The acid is the benzoate ion, Bz−. acid Bz- is the conjugate base of a weak acid (HBz). acid Therefore, the final solution is basic: Therefore, Bz− + H2O ⇄ HBz + OH− pH > 7 Bz Kb = 1.6 x 10-10 Acid­Base Reactions Acid­Base Reactions Q: Titrate 100. mL of a 0.025 M solution of benzoic acid with 0.100 M NaOH to the equivalence point. What is the pH of the f...
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This note was uploaded on 11/07/2011 for the course CHM 2045 taught by Professor Geiger during the Fall '08 term at University of Central Florida.

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