Lab 9

Titration of a Weak Acid with a Strong Base

Unit 9⏱ 90 minGuided Inquiry

Overview

How can we determine the Ka (acid dissociation constant) of a weak acid?

Objectives

How can we determine the Ka (acid dissociation constant) of a weak acid?
Connect observations to AP Chemistry models and calculations.

⚠️ Wear protective goggles and an apron. Follow your teacher’s safety directions for all chemicals and equipment.

Materials Needed

pH sensor and Drop Counter Distilled water Vernier LabQuest 100 M acetic acid 0.100 M NaOH Phenolphthalein Ring Stand Clamps Disposable pipettes Several beakers Wash bottle Stir plate Buffer solution – pH 4.0 Buffer solution – pH 10.0 Stir bars Safety glasses Graduated cylinders Printer Computer with Logger Pro interface Wear protective glasses at all times. Be careful around acids and bases

Procedure

Preparation for AP Lab#13 - (Teacher set –up) Prepare the following solutions: 0.100 M NaOH (2 liters worth) .

You will also need to make up 1 liter of a 0.100 M Acetic Acid solution and lots of DW.

Set up the laptops, pH probes, drop counters with small burettes on ring stands, DW bottles, 100-mL graduated cylinders, pipettes, phenolphthalein, stir plates, Vernier Analyzer and several beakers including a waste beaker for cleaning the small burette, a DW beakers with stir bar, 0.10 M of NaOH solution bottles, bottles of 0.10 M Acetic Acid and a beaker for distilled water.

Turn on the computer after you plug in the pH probe and Drop Counter in the Vernier Analyzer.

Go onto Loggerpro.

Go into experiment 24b in the chemistry folder.

Enter the calibration for the Drop Counter as written on the small burette.

Calibrate the pH probe with Buffer 4, Buffer 10 and DW.

(Note: you will need 3 stir bars and a stir plate).

Calibrate each probe individually.

When done, store the pH probe back in the storage solution until lab time.

Close the computer but do NOT shut it off.

Pre-Lab Questions