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why is it necessary to use de carbonated cola?

chem5.jpg
Date:
Name:
Section/Group:
Instructor:
Laboratory 8
Post-Lab: Titration of a Cola Product
Questions
1. Prepare a graph of pH versus cumulative volume of 0.1M NaOH added using Excel. Label
pKal, pKa2 and equivalence points 1 and 2. Print out a copy and turn it in. If you recorded
your data directly into Excel, also include a copy of your data.
2. Use your graph to complete the table:
Volume at first equivalence point
Volume at second equivalence point
Volume halfway to first equivalence point
Volume at half of equivalence point 2
pKa 1
pKa 2
3. What is the density of the cola? Show all of your work.
4. Using the first equivalence point, calculate the molarity of the phosphoric acid in the cola
sample. Show all of your work.
Laboratory 8 | Titration of a Cola Product
93
chem6.jpg
Name:
Section/Group:
Instructor:
Laboratory 8
Pre-Lab: Titration of a Cola Product
Questions
1. Why is it necessary to use decarbonated cola?
2. How many equivalence points does phosphoric have? How many of these equivalence points
should you be able to see in this lab?
3. The phosphoric acid in a 100.0ml sample of cola was titrated with 0.1025 M NaOH. If the
first equivalence point occurred after 16.11 ml of base was added calculate the molarity of
phosphoric acid in the cola.
4. Draw a titration curve and identify the equivalence point and the pKa.
chem7.jpg
Name:
Instructor:
Laboratory 7
Post-Lab: Weak Acids and Bases
Questions
1. Using your pH at half-equivalence for acetic acid and ammonia and considering the
Henderson-Hasselbalch equation, calculate their K, and K, values. Compare with the accepted
values and explain sources of error.
2. Explain why the pH of a solution of a weak acid or weak base is not 7.0 when it has been
neutralized to equivalence.
3. Is your buffer close to the pH that you wanted it to be? Explain sources of error.
4. How did diluting the buffer in part 4 affect the pH (did it increase or decrease, was the change
large or small)? Does this make sense given what you know about buffers and equilibrium?
Explain your reasoning.
chem8.jpg
Name:
Date:
Instructor:
Section/Group:
Laboratory 7
Pre-Lab: Weak Acids and Bases
Questions
1. Describe briefly how you plan to make 50mL of approximately 0.10M sodium acetate
(CH,COON, or NaC,H,2) solution using a small Erlenmeyer flask and a graduated cylinder.
Include calculations for the mass of sodium acetate. The actual reagent that you will probably
use is sodium acetate trihydrate, CH, COONa.3H20. Make a note of the mass of sodium
acetate trihydrate that you will need in part 3 in the "procedure and data" section before
turning in your pre-lab assignment.
2. How would you create a buffer solution at a pH of your choosing (between pH 4-6) by adding
solid sodium acetate to 50mL of 0.IM acetic acid? Use the Henderson-Hasselbalch equation to
calculate the mass of sodium acetate that you will need to produce this acetate buffer (K. = 1.75
x 10-5). Make a note of your chosen pH and the mass of sodium acetate that you will need in
part 4 in the "procedure and data" section before turning in your pre-lab assignment.
Kvolume
9 = M X ( L ) x molar mass
3. Why don't strong acids like HCI and HNO, or strong bases like NaOH have K. or K, values?
4. When does the Henderson-Hasselbalch equation not work to calculate the PH of a solution of a
weak acid or base? Explain briefly.

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Subject: Chemistry, Science

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