An acid-base indicator is usually a weak acid with a characteristic color in the protonated and deprotonated forms. In this assignment, you will monitor the color of an acetic acid solution containing Bromocresol Green as an indicator, as the pH is changed and then you will estimate the ionization constant, Ka, for the indicator. 1. Start Virtual ChemLab, select Acid-Base Chemistry, and then select Ionization Constants of Weak Acids from the list of assignments. The lab will open in the Titration laboratory. Bottles of 0.1104 M NaOH and 0.1031 M HAc (acetic acid) will be on the lab bench. The buret will be filled with the NaOH solution and a beaker containing 10.00 mL of the HAc solution will be on the stir plate. The stir plate will be on, Bromocresol Green indicator will have been added to the beaker, and a calibrated pH probe will also be in the beaker so the pH of the solution can be monitored. 2. What is the color and pH of the solution? Yellow, 2.87 3. On the buret, the horizontal position of the orange handle is off for the stopcock. Open the stopcock by pulling down on the orange handle. The vertical position delivers solution the fastest with three intermediate rates in between (slow drop-wise, fast drop-wise, and slow stream). Turn the stopcock to the second position or fast drop-wise addition. Observe the color of the solution and close the stopcock when the color turns green by double clicking on the center of the stopcock. 4. What is the color and pH of the solution now? Green, 3.80 5. Continue to add NaOH as before or at a faster rate. What is the final color of the solution? Blue 6. An acid-base indicator is usually a weak acid with a characteristic color in the protonated and deprotonated forms. Because bromocresol green is an acid, it is convenient to represent its rather complex formula as HBCG. HBCG ionizes in water according to the following equation: HBCG + H2O = BCG- + H3O+ (yellow) (blue) The Ka (the equilibrium constant for the acid) expression is: Ka BCG H3O HBCG When [BCG- ] = [HBCG], then Ka = [H3O+ ]. If you know the pH of the solution, then the [H3O+ ] and Ka can be determined. What would be the color of the solution if there were equal concentrations of HBCG and BCG- ? Green 7. What is the pH at the first appearance of this color? 3.80 What is an estimate for the Ka for bromocresol green? 1.58x10^-4 Cqan someone write aa brief conclusion of this lab for me. I have it done it but have to write a conclusion. Thank you. Preferably 7-8 sentences.

An acid-base indicator is usually a weak acid with a characteristic color in the protonated and deprotonated forms. In this assignment, you will monitor the color of an acetic acid solution containing Bromocresol Green as an indicator, as the pH is changed and then you will estimate the ionization constant, Ka, for the indicator. 1. Start Virtual ChemLab, select Acid-Base Chemistry, and then select Ionization Constants of Weak Acids from the list of assignments. The lab will open in the Titration laboratory. Bottles of 0.1104 M NaOH and 0.1031 M HAc (acetic acid) will be on the lab bench. The buret will be filled with the NaOH solution and a beaker containing 10.00 mL of the HAc solution will be on the stir plate. The stir plate will be on, Bromocresol Green indicator will have been added to the beaker, and a calibrated pH probe will also be in the beaker so the pH of the solution can be monitored. 2. What is the color and pH of the solution? Yellow, 2.87 3. On the buret, the horizontal position of the orange handle is off for the stopcock. Open the stopcock by pulling down on the orange handle. The vertical position delivers solution the fastest with three intermediate rates in between (slow drop-wise, fast drop-wise, and slow stream). Turn the stopcock to the second position or fast drop-wise addition. Observe the color of the solution and close the stopcock when the color turns green by double clicking on the center of the stopcock. 4. What is the color and pH of the solution now? Green, 3.80 5. Continue to add NaOH as before or at a faster rate. What is the final color of the solution? Blue 6. An acid-base indicator is usually a weak acid with a characteristic color in the protonated and deprotonated forms. Because bromocresol green is an acid, it is convenient to represent its rather complex formula as HBCG. HBCG ionizes in water according to the following equation: HBCG + H2O = BCG- + H3O+ (yellow) (blue) The Ka (the equilibrium constant for the acid) expression is: Ka BCG H3O HBCG When [BCG- ] = [HBCG], then Ka = [H3O+ ]. If you know the pH of the solution, then the [H3O+ ] and Ka can be determined. What would be the color of the solution if there were equal concentrations of HBCG and BCG- ? Green 7. What is the pH at the first appearance of this color? 3.80 What is an estimate for the Ka for bromocresol green? 1.58x10^-4 Cqan someone write aa brief conclusion of this lab for me. I have it done it but have to write a conclusion. Thank you. Preferably 7-8 sentences.

Chemistry: Principles and Practice

3rd Edition

ISBN:9780534420123

Author:Daniel L. Reger, Scott R. Goode, David W. Ball, Edward Mercer

Publisher:Daniel L. Reger, Scott R. Goode, David W. Ball, Edward Mercer

Chapter16: Reactions Between Acids And Bases

Section: Chapter Questions

Problem 16.9QE

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Question

An acid-base indicator is usually a weak acid with a characteristic color in the protonated and

deprotonated forms. In this assignment, you will monitor the color of an acetic acid solution

containing Bromocresol Green as an indicator, as the pH is changed and then you will estimate

the ionization constant, Ka, for the indicator.

1. Start Virtual ChemLab, select Acid-Base Chemistry, and then select Ionization Constants of

Weak Acids from the list of assignments. The lab will open in the Titration laboratory. Bottles of

0.1104 M NaOH and 0.1031 M HAc (acetic acid) will be on the lab bench. The buret will be filled

with the NaOH solution and a beaker containing 10.00 mL of the HAc solution will be on the stir

plate. The stir plate will be on, Bromocresol Green indicator will have been added to the beaker,

and a calibrated pH probe will also be in the beaker so the pH of the solution can be monitored.

2. What is the color and pH of the solution?

Yellow, 2.87

3. On the buret, the horizontal position of the orange handle is off for the stopcock. Open the

stopcock by pulling down on the orange handle. The vertical position delivers solution the

fastest with three intermediate rates in between (slow drop-wise, fast drop-wise, and slow

stream). Turn the stopcock to the second position or fast drop-wise addition. Observe the color

of the solution and close the stopcock when the color turns green by double clicking on the

center of the stopcock.

4. What is the color and pH of the solution now?

Green, 3.80

5. Continue to add NaOH as before or at a faster rate. What is the final color of the solution?

Blue

6. An acid-base indicator is usually a weak acid with a characteristic color in the protonated and

deprotonated forms. Because bromocresol green is an acid, it is convenient to represent its

rather complex formula as HBCG. HBCG ionizes in water according to the following equation:

HBCG + H2O = BCG- + H3O+ (yellow) (blue) The Ka (the equilibrium constant for the acid)

expression is: Ka

BCG

H3O

HBCG When [BCG- ] = [HBCG], then Ka = [H3O+ ]. If you

know the pH of the solution, then the [H3O+ ] and Ka can be determined.

What would be the color of the solution if there were equal concentrations of HBCG and BCG- ?

Green

7. What is the pH at the first appearance of this color?

3.80

What is an estimate for the Ka for bromocresol green?

1.58x10^-4

Cqan someone write aa brief conclusion of this lab for me. I have it done it but have to write a conclusion.

Thank you. Preferably 7-8 sentences.

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