prelimlab10 - Objective The purpose of this lab is further understanding of acid/base equilibria through experiments in buffer action and the use of

Objective: The purpose of this lab is further understanding of acid/base equilibria through experiments in buffer action and the use of acid/base reactions for analysis. Procedure: A. Buffers 1. Calculate the number of moles of acetic acid in a 100 mL sample of vinegar and it’s concentration in moles/L [M]. Data: MW=60, Ka=1.8x10 -5 , density=1.01 g/ml. 2. Setup a TI/CBL2 with a pH sensor and calibrate with standard known buffers 4 and 7. Rinse with DI water between measurements and blot dry with Kimwipe. 3. Make 2 samples of 100 ml of acetic acid buffer at pH 5 using these two methods: a. Add 3-5 drops universal indicator to 100 ml of commercial vinegar. Calculate exact amount of solid sodium acetate trihydrate (MW=136.08) that needs to be added to solution to make buffer of pH=5. Record pH. b. Divide 20 ml of commercial vinegar into two 10 ml portions. Add 3-4 drops phenolphthalein indicator to one of them. Add 1.0 M NaOH to this one slowly until it turns light pink. Mix two solutions back together and measure pH and record, then adjust to pH 5 by adding 6 M NaOH. Record