CHEM120 W5 Lab Template 1

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CHEM120 W5 Lab Template 1
Heather iLab, Week #5



The purpose of the week 5 ilab is to describe the principles of pH measurements and predict the corrosion tendencies of solutions based on pH. It is to determine the concentration of an unknown acid by using the chemistry of the acid-base titration to calculate the concentration of the unknown acid. In order to calculate the concentration of the unknown acid you have to use a pH indicator, which will change color based on the pH of the acid.
This is the equipment needed in this experiment:
 100 mL beaker
 general purpose thermometer in oC
 pH meter

2. 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
Part 1:
1. Set up two 50 mL test tubes.
2. Label one as an Acid “A” and one as a Base “B”
3. Place 35 mL of the appropriate stock solution into each test tube
4. Add 5 drops of an indicator into each test tube.
5. Record the resultant color for the acid and base.
6. Repeat for the other 4 Acid - Base Indicators

Part 2
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

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