Thursday, January 26, 2012

pH Lab

        pH LAB

HYPOTHESIS: Lemon juice, dish cleaner, vinegar, and ammonia are going to be acidic, and the others basic.

household solutions
Vernier computer interface
7 small test tubes
Logger Pro
test-tube rack
Vernier pH Sensor
blue litmus paper
wash bottle
paper towel
distilled water
stirring rod
ring stand
red cabbage juice
utility clamp
250 mL beaker
sensor soaking solution  

Part I  Litmus Tests
Obtain a pair of goggles so that you may protect your eyes from any acidic splash from the contents you are about to be exposed to. Label 6 test tubes with the numbers 1–6 and place them in a test-tube rack. Measure 3 mL of vinegar into test tube 1. Refer to the data table and fill each of the test tubes to about the same level with its respective solution. Ammonia solution is toxic. Its liquid and vapor are extremely irritating, especially to eyes. Handle these solutions with care. Do not allow the solutions to contact your skin or clothing. Wear goggles at all times. Notify your teacher immediately in the event of an accident. Use a stirring rod or dropper, to transfer one drop of vinegar to a small piece of blue litmus paper on a paper towel. Transfer one drop to a piece of red litmus paper on a paper towel. Record the results. Clean and dry the stirring rod each time. Test the other solutions using the same procedure. Be sure to clean the stirring rod or dropper each time.

Part II  Red Cabbage Juice Indicator
After you have finished the Part I litmus tests, add 3 mL of red cabbage juice indicator to each
of the 7 test tubes. Record your observations. Dispose of the test-tube contents as directed by
your teacher.

Part III  pH Tests
Connect the pH Sensor to the computer interface. Prepare the computer to monitor pH by opening the file “21 Household Acids” from the Chemistry with Vernier folder. Raise the pH Sensor from the sensor storage solution and set the solution aside. Use a wash
bottle filled with distilled water to thoroughly rinse the tip of the sensor as demonstrated by
your instructor. Catch the rinse water in a 250 mL beaker. Get one of the 7 solutions in the small container supplied by your sensor. Raise the solution to the pH Sensor and swirl the solution about the sensor. When the pH reading stabilizes, record the pH value in your data table.

Household Acids and Bases
Prepare the pH Sensor for reuse. Rinse it with distilled water from a wash bottle.
Place the sensor into the sensor soaking solution and swirl the solution about the sensor briefly. Rinse with distilled water again. Determine the pH of the other solutions using the Step 9 procedure. You must clean the sensor, using the Step 10 procedure, between tests. When you are done, rinse the tip of the sensor with distilled water and return it to the sensor soaking solution.

1. Which of the household solutions tested are acids? How can you tell?
Lemon juice, Dish cleaner, Ammonia were acidic. We could tell by the blue litmus paper.
2. Which of the solutions are bases? How can you tell?
Vinegar, Ammonia, Laundry Detergent. We could tell by the shade the blue Litmus paper gave off.
3. What color(s) is red cabbage juice indicator in acids? In bases?
In acids it is a pink or green color and in some bases it would not mix at all.
4. Can red cabbage juice indicator be used to determine the strength of acids and bases? Explain. I think it does not because we had a variation in the shade or the colors and it was difficult to find any distinguishable colors or patterns within our experiments.
5. List advantages and disadvantages of litmus and red cabbage juice indicators.  
The advantage of Litmus is it gives you a color easily compared on the pH scale but the disadvantage is it isn't exact and the color can sometime not be perfectly matched so we have to guess somewhere in between. Red cabbage is good when it come to large amounts of the color but bad if you want a more exact answer.

CONCLUSION: My hypothesis was incorrect and vinegar and Ammonia were not as acidic as I had expected and were instead more of a basic compound.

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