University of Toronto Chemistry Titration of Vinegar Lab Report

TITRATION OF VINEGAR [10 MARKS]C2H4O2
ACETIC ACID
+ NaOH
+
→
NaCH3COO
SODIUM HYDROXIDE → SODIUM ACETATE
+
+
H2O
WATER
https://youtu.be/QvpNwBzkYDg
Objective:
The objective of this laboratory is to determine the molarity and the % by mass of acetic acid in vinegar.
The formula for acetic acid can be written as C2H4O2 OR AS CH3COOH
Preparation
1. Rinse the buret with ~ 5mL of deionized water followed with the standardized 0.1113M NaOH
solution. Secure the buret with the clamp to a retort stand.
2. Fill the buret with the 0.1113M NaOH solution.
3. Flush the buret tip to remove the trapped air bubbles.
4. Record the initial reading of 0.1113 M NaOH in the buret for Trial 1
5. Using the bulb, suction some deionized water into the pipette to rinse. Repeat this process with
vinegar.
6. After rinsing, draw in exactly 5.00 mL of vinegar into the pipette and transfer to a volumetric flask.
7. Add 20.00 mL of distilled water and 5 drops of phenolphthalein to the flask.
8. Position the mouth of the flask under the buret. You will manually stir the solution.
Titration
9. Add NaOH until a pink colour can be detected. Slow down and go drop by drop until the entire
solution in the flask remains a faint pink colour for 30 seconds.
10. Record the final volume of NaOH used to reach the end point. This is the point when the indicator
changes colour. It is also the equivalence point when all the moles of acid in the vinegar have been
neutralized by the moles of base.
11. Normally this lab should be conducted in triplicate for more accuracy, however to save on time there
was only one trial done. Record your initial volume reading of the buret and the final buret reading in
the chart below.
Experimental Data [ 3 marks]
Trial 1
(a) Initial Buret reading
(b) Final Buret reading
(c) Volume of NaOH
used (final – initial)
(d) Molar of NaOH
(e) Volume of vinegar
used
0.1113M
5.0 mL
Calculation
Using the methods shown in Unit 4 Module 3, calculate the concentration of acetic acid in the commercial
vinegar sample. Fill in all given values at the side before you begin your solution. Full solutions must be
shown for full marks. [3 marks]
C2H4O2
+
NaOH
→
NaCH3COO
+
H2O
Ca=?
Va=
Cb=
Vb=
na=
nb=
Questions
Questions 1. If there were other acids in addition to acetic acid present in vinegar, how would this affect
your results? Explain. [2]
Question 2. If your solution was too pink, how would this affect your calculated concentration of acid?
Explain. [2]