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MM and IC of WA - Introduction The purpose of this lab is...

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1 Introduction The purpose of this lab is to determine the molar mass and acid dissociation constant of acetic acid by titration and pH measurement of solutions containing a known mass concentration of acetic acid. Also, we will be determining the molar mass and acid ionization constant of an unknown weak acid. A pH meter will be used to help determine pH levels. Acetic Acid will be used which has a molar mass of 60.05 g/mol and a pK a of 4.75. Relevant Formulas/Diagrams HA + H 2 O H 3 O + + A - CH 3 COOH + H 2 O H 3 O + + CH 3 COO - Procedure 1. Take 20 grams of acetic acid and find the pH. Transfer acid to flask and add 10 more ml giving a solution of 30ml in the flask. 2. Added 5 drops of 0.1% thymol blue indicator. Titrate solution using NaOH until a blue color is visible. Record volume of NaOH. 3. Repeated steps 1 and 2 4. Add 30 ml of acetic acid to flask and exactly half of the NaOH used in titrations of step two. 5. Determine pH using pH meter. 6. Repeated steps 4 and 5 7. Take unknown acid A and repeat steps one through six. 8. Using the Molar Mass and pK a from these numbers, the unknown acid was determined. Data Part 1: Concentration of NaOH = 0.097 M Trial 1 Trial 2 Measured pH of Acetic acid solution 3.01 3.01 Mass of acetic acid taken for titration 29.988 g 29.984 g Initial Vol. reading 0 mL 0 mL Final Vol. reading 12.6 mL 12.45 mL Net Vol. NaOH 12.6 mL 12.45 mL mMol NaOH used 1.22 mMol 1.208 mMol
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in titration
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