Chm 130 Lab 12

Topics: PH, Acid, PH indicator Pages: 5 (1003 words) Published: April 12, 2015


Vicente Viloria
CHM 130 LL
Section 22258
Lab 12: Introduction to pH, Household Products and Buffers
12/9/14

Introduction
In this experiment the students will be determining the pH of household products along with other solutions using several different indicators as well as a pH meter. The experiment also has the student determining what the buffer solution is in an aqueous solution. The student will also be testing the pH of milk of magnesia and will see how it affects the stomach acid. Lastly the student will be using the carbon dioxide found in their breath to neutralize a base. Apparatus and experimental setup

Experiment:
A. pH measurement with indicators and pH meter
In this experiment the student will need a Bunsen burner, ring stand, wire gauze, pH meter, red cabbage, about seven small beakers (clean), seven test tubes, universal pH paper, both red and blue litmus paper, methyl red and several solutions provided by the instructor. First the student will prepare the red cabbage by filling a beaker with 50 mL of distilled water and placing about 1 gram of finely chopped red cabbage and boil for 10 minuets. Let the beaker cool and decant the solution from the cabbage. While the cabbage is boiling the student should continue with the rest of the experiment, pour about 2 mL into the beaker and test the pH with the pH meter, litmus papers, and universal pH paper and record. Pour half of the solution into a test tube and set aside. With the sample in the beaker add 2 drops of methyl red and record. With the solution in the test tube add a dropper full of the cabbage indicator and record. The student must do these steps with all of the solution provided for in this experiment.

B. Buffer solutions
For this experiment the student will need four beakers, baking soda and a pH meter. In one beaker put 50 mL of distilled water into it and mix about a tablespoon full of baking soda with it. Take the pH of the solution and record. Divide the solution into two portions. To one portion add 2 drops of 1 M HCl and mix. To the other portion add 2 drops of 1 M NaOH and mix. Now the student will take the pH of both solutions with a pH meter and record. In two separate beakers add 25 mL of distilled water to both. To one beaker add 2 drops of 1 M HCl and mix. To the other add 2 drops of 1 M NaOH and mix. Next the student will take the pH of both solutions with a pH meter and record. C. Milk of magnesia on stomach acid

For this experiment the student will need 2 50 mL beakers (clean) and a pH meter or universal pH paper. Place 20 mL of 1 M HCl into one beaker and test the pH and record. Divide the HCl into two portions, to one add 1 teaspoon of distilled water, stir, take the pH and record. To the other add milk of magnesia (Mg(OH)2) stir and check the pH and record. D. Action of carbon dioxide in your breath for the neutralization of a base For this experiment the student will need a test tube, a straw, phenolphthalein indicator, and calcium hydroxide. The student will first add a very small amount of calcium hydroxide (about 1/8 of a dropper full) into a test tube. Next check the pH by adding 2 drops of phenolphthalein indicator (colorless in acid, bright pink in base). Annotate what the color is when the indicator is added. Now using a straw blow bubbles into the solution until the solution color changes.

Data Collected
A. pH measurement with indicators and pH meter

Solution
Indicators

Cabbage

pH meter
Universal pH paper
Litmus paper
Methyl red

Red
Blue

A
4.51
6
2
2
Magenta
Pink
B
6.99
8
10
11
Yellow
Yellow
C
9.65
10
11
12
Yellow
Light green
Lemon juice
3.18
2
3
2
Light pink
Light
pink
M.O.M.
8.30
8
10
10
Yellow
Green
Tap water
7.80
7
7
10
Yellow
Purple

Milk
6.21
8
10
9
Light orange

Purple

B. Buffer solutions

pH value
System tested
Baking soda solution
Distilled water...
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