Lab - The Titration of Vinegar

PRE-LAB QUESTIONS

1. Why are you using phenolphthalein as an indicator?

2. Estimate the volume reading for the burette depicted in Figure 10.1.

3. Distinguish between the endpoint and equivalence point.

4. If 12.66 mL of 0.250 M NaOH solution is used in a titration how many moles of OH^- were added? How many moles of H⁺ could be neutralized with this amount of hydroxide?

POST-LAB QUESTIONS -

1. Discuss the main sources of error in this experiment.

2. Sally Chemist is attempting to determine the mass % of acetic acid in vinegar using the experimental procedure described above. Below is an excerpt from her lab book:

a. Prepared vinegar analyte

25.0 mL vinegar

Mass of vinegar = 25.20 g

Added 75.0 mL H₂O

Added 2 drops phenolphthalein

Temperature: 27.0^oC

Manufacturer's mass % acetic acid = 3.5%

b. Prepared burette

Cleaned and dried burette

Filled with standardized NaOH solution 0.201 M

c. Titration

Initial burette reading: 5.12 mL

Final burette reading: 78.67 mL

Solution is light pink

Room temp unchanged.

i. What is the density of her vinegar sample?

ii. Use the manufacturers reported mass % acetic acid to estimate how many moles of acetic acid are present in her analyte.

iii. Use your result from ii to estimate how many mL of standardized NaOH solution she will need to reach the equivalence point.

iv. Use Sally's data to calculate the molarity of acetic acid in her vinegar sample.

v. Use the results from iv to calculate the mass % of acetic acid in Sally's vinegar sample.

vi. How would the following experimental errors affect Sally's experimental result?

DATA ANALYSIS -

1. Calculate the following for each trial and average the values:

a. Moles of NaOH used

b. Moles of acetic acid reacted

c. Mass in grams of acetic acid reacted

d. Molar concentration of acetic acid

e. Mass % of acetic acid

2. Calculate the percent error between your average experimental value of the mass % of acetic acid in vinegar and the manufacturer's reported mass % of acetic acid in vinegar.

Attachment:- Assignment Files.rar