Devry week five chem Ilab

Lacy Taylor iLab, Week #5

UNKNOWN ACID AND BASE TITRATION

Introduction
The pH, or the concentration of the hydrogen plus ion [H+], is one of the most critical parameters in predicting if a system will corrode, or determining why a system is corroding. PH is defined as the negative log base 10 of the hydrogen plus ion concentration in the units of moles per litre.

Procedure

pH MEASUREMENT OF UNKNOWN SOLUTIONS

Obtain the following apparatus from the equipment menu:

 100 mL beaker
 general purpose thermometer in oC
 pH meter

Obtain a sample unknown that you wish to determine the pH of, and place about 50 mL in the beaker.

3. Lower the electrode into the solution, and while gently stirring, determine the pH of the solution

ACIDITY MEASUREMENT WITH INDICATORS

Set up two 50 mL test tubes.
Label one as an Acid “A” and one as a Base “B”
Place 35 mL of the appropriate stock solution into each test tube
Add 5 drops of an indicator into each test tube.
Record the resultant color for the acid and base.
Repeat for the other 4 Acid - Base Indicators

PART 2 - ACID/BASE TITRATION

PROCEDURE

Step 1: Obtain acid, in a 100 ml Erlenmeyer flask add 35 ml of an Unknown HCl solution.

Step 2: Add an indicator to the acid, select the flask and add 2 drops of phenolphthalein indicator. The indicator menu is available under the chemicals main menu (ChemicalsIndicators) or the context menu.

Step 3: Fill buret with NaOH, obtain a 50 ml buret and fill with .100M NaOH solution.

Step 4: Titrate NaOH into HCl until end point, record initial buret volume and add NaOH (quickly at first then slowly) until the HCl solution turns pink and record the final buret volume of NaOH in buret.

Step 5 repeat steps 1-4 using pH meter, add a pH meter to the acid solution. Record numerous points of pH and NaOH added (especially near equivalence point) to be used later to prepare a titration curve.

Observations and Results