Lab 5-1B: Properties of Acids and Bases Amanda Stanyer Block B
Purpose: In this lab I hope to use properties of solutions in order to find out the relative strengths of sifferent acids and/or bases.
Questions before we start the lab:
Q1. How will magnesium ribbon help you in this lab?
A: It cam tell us the acidity of a substance by the amount of bubbles it shows.
Q2. In general, what information can chemical indicators give you?
A: They indicate the pH level of a substance.
Q3. For each indicator below, briefly show on the scale the colour(s) at different pH levels.
a. Red litmus. 0-6.9: red 7.1-14: blue
b. Blue litmus. 0-6.9: red 7.1-14: blue
c. Bromothymol blue. 0-6.9: yellow 7.1-14: blue
d. Indigo carmine. 0-11.9: blue 12.1-14: yellow
e. Methyl orange. 0-2.9: red 3.1-14: yellow
Materials:
- 4x6 spot plate
- masking tape
- Solutions A, B, C, and D
- 4 pieces of Mg ribbon
- 4 pieces of red litmus paper
- 4 pieces of blue litmus paper
- bromothymol blue solution
- indigo carmine solution
- methyl orange solution
Procedure:
1. Use masking tape to label the rows on the spot plate with A, B, C, and D.
2. Add a few mL of solution A to the 6 wells of row A on the spot plate. Repeat for rows B, C, and D.
3. Place a piece of Mg ribbon in the first well of each of the four rows.
4. Place a piece of red litmus paper in the second well of each row, and place a piece of blue litmus paper in the third well of each row.
5. Add five drops of bromothymol blue solution to the fourth well of each row, and repeat with indigo carmine and methyl orange solutions for the fifth and sixth rows.
6. Record results in the data table. State the colour or other observations.
7. Have the teacher check your work.
8. Clean up. Follow the teacher's instructions for disposal of wastes.
Results:
A. Mg ribbon: bubbles; Red litmus: red; Blue litmus: orange; Bromothymol blue: yellow; Indigo carmine: dark blue; Methyl orange: red.
B. Mg ribbon: no bubbles; Red litmus: blue; Blue litmus: blue; Bromothymol blue: blue; Indigo carmine: dark green; Methyl orange: orange.
C. Mg ribbon: bubbles; Red litmus: red; Blue litmus: pinkish purple; Bromothymol blue: turquoise; Indigo carmine: dark blue; Methyl orange: orange.
D. Mg ribbon: no bubbles; Red litmus: purple; Blue litmus: purple; Bromothymol blue: blue; Indigo carmine: dark blue; Methyl orange: orange, milky in comparison to other methyl orange solutions.
Discussion:
Analyze:
1. From most acidic to least acidic: A, C, D, B
2. Neutral: D. Because for the red & blue litmus, it was purple. Red + blue = purple so it was somewhere near the middle of the pH spectrum.
3. D and B were bases. B was more basic because with the red litmus, it turned blue, whereas D turned purple. Also, with the indigo carmine, B was the only one that turned green while all the other ones stayed blue.
4. If there are bubbles with the Mg ribbon, it is acidic.
Conclude and Apply:
1. a) In a pH 3 solution:
Litmus: red
Bromothymol blue: yellow
Indigo carmine: blue
Methyl orange: red
b) In a pH 10 solution:
Litmus: blue
Bromothymol blue: blue
Indigo carmine: blue
Methyl orange: yellow
2. I would use red litmus, blue litmus and bromothymol blue because those seemed to give the best and clearest results.
3. Red
4. Blue
5. a) Pacific Ocean
b) North and South Poles
