HND Biomedical Sciences Lab Report

Determination of the concentration of ethanoic acid in commercial vinegar
Introduction:
The aim of the experiment was to determine the molarity of ethanoic acid in table vinegar by titrating a sample with alkali sodium hydroxide (NaOH) with a known concentration of 0.1molL-1. The equation of the reaction between ethanoic acid and sodium hydroxide is as follows:
CH3COOH + NaOH CH3COONa + H2O
When the titrations end point is determined and volumes of reactants are measured the concentration of the ethanoic acid can be calculated.
Keywords: Titration, Sodium Hydroxide, Ethanoic Acid, Equivalence Point, pH Meter, Standard Solution
Method:
Using a bulb pipette 25cm3 of vinegar was measured into a 250cm3 standard flask and using deionised water the total volume was made up to 250cm3. A second bulb pipette was used to measure 25cm3 of the prepared solution into a clean 100cm3 conical flask. A clean burette was set up and rinsed with a small volume of 0.1molL-1 NaOH then filled to the start level with NaOH of the same concentration. The vinegar was then titrated with the NaOH and the pH was recorded every few cm3 of NaOH that was used. From the results the concentration of the ethanoic acid was calculated.
Results
Burette Reading pH Burette Reading pH Burette Reading pH 50
2.7
25
6.95
11
11.77
48
2.96
24
8.05
10
11.79
46
3.5
23
8.75
9
11.81
44
3.79
22
8.98
8
11.84
42
4.24
21
9.44
7
11.85
40
4.49
20
10.14
6
11.88
38
4.64
19
10.68
5
11.90
36
4.69
18
11.10
4
11.91
34
4.71
17
11.29
3
11.93
32
4.73
16
11.49
2
11.94
30
5.78
15
11.52
1
11.95
28
6.12
14
11.59
0
12
27
7.05
13
11.70

26
7.04
12
11.75

Calculations:
Volume of CH3COOH = 0.025l
Volume of NaOH = 0.0145l
Concentration of NaOH = 0.1molL-1

Moles of NaOH = 0.0145 x 0.1 = 0.00145molL-1

Concentration of diluted ethanoic acid = 0.00145 0.025