Chemistry Investigatory Project
Chemistry Investigatory Project
Chemistry Investigatory Project
AMOUNT OF
ACETIC ACID
IN VINEGAR
Shreyansh Malhan
XII A
:: Index ::
1. Certificate
2. Aim
3. Acknowledgement
4. Objective
5. Introduction
6. Apparatus
7. Theory
8. Experimental Procedure
9. Experiment 1
10. Experiment 2
11. Experiment 3
12. Result
13. Precautions
14. Bibliography
:: OBJECTIVE ::
Titration introduction:
In this project, I have determined the amount of acid in different
vinegars using titration, a common technique in chemistry. Titration is
a way to measure the unknown amount of a chemical in a solution (the
titrant) by adding a measured amount of a chemical with a known
concentration (the titrating solution). The titrating solution reacts
with the titrant, and the endpoint of the reaction is monitored in
some way. The concentration of the titrant can now be calculated
from the amount of titrating solution added, and the ratio of the two
chemicals in the chemical equation for the reaction.
Titration theory:
To measure the acidity of a vinegar solution, we can add enough
hydroxyl ions to balance out the added hydrogen ions from the acid.
The hydroxyl ions will react with the hydrogen ions to produce water.
In order for a titration to work, we need three things:
1. a titration solution (contains hydroxyl ions with a precisely known
concentration),
2. a method for delivering a precisely measured volume of the
titrating solution, and
3. a means of indicating when the endpoint has been reached. For
the titrating solution, we'll use a dilute solution of sodium hydroxide
(NaOH). Sodium hydroxide is a strong base, which means that it
dissociates almost completely in water . So for every NaOH molecule
that we add to the solution,we can expect to produce a hydroxyl ion.
Performing titration:
To dispense an accurately measured volume of the titrating solution,
we will use a burette. A burette is a long tube with a valve at the
bottom and graduated markings on the outside to measure the volume
contained in the burette. The burette is mounted on a ring stand,
directly above the titrant solution . Solutions in the burette tend to
creep up the sides of the glass at the surface of the liquid. This is due
to the surface tension of water. The surface of the liquid thus forms
a curve, called a meniscus. To measure the volume of the liquid in the
burette, always read from the bottom of the meniscus.
Indicators:
In this experiment, we will use an indicator solution called
phenolphthalein. Phenolphthalein is colourless when the solution is
acidic or neutral. When the solution becomes slightly basic,
phenolphthalein turns pinkish, and then light purple as the solution
becomes more basic. So when the vinegar solution starts to turn pink,
we know that the titration is complete.
:: APPARATUS ::
To do this experiment we will need the following materials and
equipment:
➔Vinegar, three different types.
➔Distilled water
➔Small funnel
➔0.5% Phenolphthalein solution in alcohol (pH indicator solution)
➔0.1 M sodium hydroxide solution
➔125 mL Conical flask
➔25 or 50 mL burette
➔10 mL graduated cylinder
➔Ring stand
➔Burette clamp
:: THEORY ::
Required amount of sodium hydroxide (NaOH) can be calculated using
the following formula:
Molarity X Molar Mass X Volume
W= (cm3)
1000
Molar mass of NaOH = 40 g/mol
0.5
=
= 10 g
Indicator:- Phenolphthalein
End Point:- Colourless to pink
:: EXPERIMENTAL PROCEDURE ::
1. Pour 1.5 ml of vinegar in an Conical flask.
2. Add distilled water to dissolve the vinegar so that the volume of
the solution becomes 20 mL.
3. Add 3 drops of 0.5% phenolphthalein solution.
4. Use the burette clamp to attach the burette to the ring stand.
The opening at the bottom of the burette should be just above the
height of the Conical flask we use for the vinegar and
phenolphthalein solution.
5. Use a funnel to fill the burette with a 0.1 M solution of sodium
hydroxide.
6. Note the starting level of the sodium hydroxide solution in the
burette. Put the vinegar solution to be titrated under the burette.
7. Slowly drip the solution of sodium hydroxide into the vinegar
solution. Swirl the flask gently to mix the solution, while keeping the
opening underneath the burette.
8. At some point we will see a pink colour in the vinegar solution
when the sodium hydroxide is added, but the colour will quickly
disappear as the solution is mixed. When this happens, slow the
burette to drop-by-drop addition.
9. When the vinegar solution turns pink and remains that colour even
with mixing, the titration is complete. Close the tap (or pinch valve)
of the burette.
10. Note the remaining level of the sodium hydroxide solution in the
burette. Remember to read from the bottom of the meniscus.
11. Subtract the initial level from the remaining level to figure out
how much titrating solution we have used.
12. For each vinegar that we test, repeat the titration at least three
times.
:: EXPERIMENT 1 ::
Take the laboratory vinegar in the conical flask and do the titration with
NaOH as mentioned.
OBSERVATIONS:-
Sr Volume in Vinegar Burette Reading Volume of
No. Solution (in ml) NaOH
Initial (in Final (in
solution used (in
ml) ml)
ml)
1 20 0 15.2 15.2
2 20 0 15.2 15.2
3 20 0 15.2 15.2
Concordant Value = 15.2 ml
CALCULATIONS:-
We know that:-
MCH COOH X VCH COOH=M NaOH X VNaOH
3 3
M XV
MCH COOH=
3 NaOHVCH3COOHNaOH
=
MCH COOH
3 0.5
= 0.38 mol/L
Strength of acetic acid = 0.38 X 60 g/L =
22.8 g/L
:: EXPERIMENT 2 ::
Take the household vinegar in the conical flask and do the titration with
NaOH as mentioned.
OBSERVATIONS:-
1 10 0 13.5 13.5
2 10 0 13.5 13.5
3 10 0 13.5 13.5
CALCULATIONS:-
We know that:-
MCH COOH X VCH COOH=M NaOH X VNaOH
3 3
M XV
MCH COOH=
3 NaOHVCH3COOHNaOH
= 0.5
MCH COOH
3
= 0.675 mol/L
Strength of acetic acid = 0 .675 X 60
=40.5 g/L
:: EXPERIMENT 3 ::
Take the wine vinegar in the conical flask and do the titration with
NaOH as mentioned.
OBSERVATIONS:-
Sr Volume of Burette Reading Volume of NaOH
No. Vinegar Initial (in Final (in solution used (in ml)
solution(in ml) ml) ml)
1 10 0 24 24
2 10 0 24 24
3 10 0 24 24
Concoradant Volume = 24 ml
CALCULATIONS:-
We know that:-
MCH COOH X VCH COOH=M NaOH X VNaOH
3 3
M XV
MCH COOH=
3 NaOHVCH3COOHNaOH
= 0.5
MCH COOH
3
= 1.2 mol/L
Strength of acetic acid = 1.2 X 60 g/L = 72
g/L
Strength of acetic acid in laboratory vinegar = 22.8 g/L
Strength of acetic acid in household vinegar = 40.5 g/L
Strength of acetic acid in wine vinegar = 72 g/L
70
60
50
40
30
20
10
0
Laboratory Vinegar Household Vinegar Wine Vinegar