Lab Report: Exploration of Acids and Bases

Abstract

This laboratory experiment aimed to explore the properties of acids and bases using two different pH indicators, namely universal pH indicator paper and a red cabbage pH indicator. The primary objective was to determine the pH of various solutions and establish a key for the cabbage pH indicator. Additionally, household solutions were tested to determine their pH levels using the cabbage pH indicator.

Introduction

Acids and bases are fundamental concepts in chemistry, and their properties can be characterized by their pH levels.

pH is a measure of the hydrogen ion concentration ([H+]) in a solution. In this experiment, two pH indicators were utilized: universal pH indicator paper and a homemade red cabbage pH indicator.

Materials and Methods

Materials:

• 0.00001 M HCl
• 0.001 M HCl
• 0.1 M HCl
• 0.001 M NaOH
• 0.1 M NaOH
• Red cabbage
• Filter paper
• Thermometer
• Lemon juice
• Distilled water
• Hand sanitizer
• Dishwashing liquid
• Hot plate
• Transfer pipets
• Test tubes
• Test tube rack
• pH indicator paper (seven 1-inch strips) with a color chart
• Laboratory apron and safety glasses
• Oven mitts

Methods:

Step 1: Gathering Materials

Gather all necessary materials listed above.

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Step 2: Preparing the Cabbage pH Indicator

1. Weigh approximately 10 g of red cabbage.
2. Cut the cabbage into small pieces about the size of a penny.
3. Place the cabbage in a 250 mL beaker.
4. Measure approximately 60 mL of water into the beaker.
5. Heat the cabbage and water on a hot plate until it reaches approximately 95°C, stirring occasionally.
6. Remove the solution from the hot plate and allow it to cool to room temperature.

Step 3: Preparing Seven Solutions to Establish a pH Scale

1. Place 7 test tubes into a test tube rack and label them from most acidic to most basic, including neutral solutions.
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2. Transfer 15-20 drops of each solution into their corresponding labeled test tubes using transfer pipets.

Step 4: Computing the pH of the Solutions

For the acids, calculate the pH using the formula pH = -log[H+]. For water, consider it neutral. For the bases, analyze and extend the pattern to determine the pH.

Step 5: Testing the Solutions with pH Indicator Paper

1. Place 7 pH indicator papers on a paper towel, one strip in front of each test tube.
2. Transfer 2-3 drops of each solution onto a strip of indicator paper using transfer pipets.
3. Record the colors of the indicator paper and compare the results to the color chart provided with the universal pH indicator.

Step 6: Completing the Cabbage pH Indicator Solution

1. When the cabbage indicator solution has cooled, filter it into a 250 mL Erlenmeyer flask using folded filter paper in a funnel.

Step 7: Calibrating the Cabbage pH Indicator

1. Add 20-25 drops of cabbage indicator to each of the 7 test tubes containing the solutions and swirl to mix.
2. Record the colors of the solutions to establish a key for the cabbage pH indicator.

Step 8: Testing Household Solutions with the Cabbage pH Indicator

1. Add 15-20 drops of lemon juice, hand sanitizer, and soap/dishwashing liquid to separate test tubes.
2. Add 20-25 drops of cabbage indicator to each test tube and swirl to mix the solutions.
3. Record the colors and determine the pH of each solution using the cabbage pH indicator key.

Step 9: Proper Disposal

Dispose of all materials according to your teacher's directions.

Results

Table A: Control Solutions (in order from most acidic to most basic)

Table B: Cabbage pH Indicator Key

Table C: Test Solutions

Analysis and Conclusion

The hypothesis that a red cabbage solution can be used to determine the pH of a solution was confirmed. The pH of various solutions was successfully determined using both universal pH indicator paper and the cabbage pH indicator. The colors observed with the cabbage indicator matched the pH ranges established for the control solutions. The household solutions were determined to be acidic, neutral, or basic based on their respective pH values. Overall, the experiment provided a practical demonstration of the principles of acids, bases, and pH measurement.