Month: December 2017

Measuring the Amount of Acetic Acid In Vinegar

 

S.No.		Contents	II	Page No.
I.		Introduction
II.		Materials And Equipments
III.		Theory
V.		Experimental Procedure
VI.		Experiment 1
VII.		Experiment 2
VIII.		Experiment 3
IX.		Result
X		Precaution
XI.		Bibliography

Introduction

Vinegar is a solution made from the fermentation of ethanol (CH₃CH₂OH), which in turn was previously fermented from sugar. The fermentation of ethanol results in the production of acetic acid (CH₃COOH). There are many different types of vinegar, each starting from a different original sugar source (e.g., rice, wine, malt, etc.). The amount of acetic acid in vinegar can vary, typically between 4 to 6% for table vinegar, but up to three times higher (18%) for pickling vinegar.

In this project, we will determine the amount of acid in different vinegar 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.

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.

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 (as shown in the picture).

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.

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.

Materials and Equipment

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:

W = Molarity x Molar mass x Volume(cm )
=1000

Molar mass of NaOH = 40 g/mol =   0.5 x 40 x 500 ~        1000 =    10 g

The acetic acid content of a vinegar may be determined by titrating a vinegar sample with a solution of sodium hydroxide of known molar concentration (Molarity).

CH3COOH(aq) + NaOH(aq)     CH3COONa(aq) + H2O(l) (acid) + (base) — > (salt) + (water)

At the end point in the titration stoichiometry between the both solution lies in a 1:1 ratio.

^MCH₃COOH^VCH₃COOH      1

^MNaOH^VNaOH                         ¹

Strength of acid in vinegar can be determined by the following formula:

Strength of acetic acid = M_{CH COOH} x 60

Indicator:- Phenolphthalein End Point:- Colourless to pink

Experimental Procedure

Performing the Titration

1. Pour 1.5 ml of vinegar in an Conical flask.
   1. Add distilled water to dissolve the vinegar so that the volume of the solution becomes 20 mL.
   2. Add 3 drops of 0.5% phenolphthalein solution.
      1. 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.
      2. Use a funnel to fill the burette with a 0.1 M solution of sodium hydroxide.
      3. Note the starting level of the sodium hydroxide solution in the burette. Put the vinegar solution to be titrated under the burette.
      4. 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.
      5. 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.

1. 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.
2. Note the remaining level of the sodium hydroxide solution in the burette. Remember to read from the bottom of the meniscus.
3. Subtract the initial level from the remaining level to figure out how much titrating solution we have used.
4. For each vinegar that we test, repeat the titration at least three times.

EXPERIMENT – 1

I.   Take the household vinegar in the conical flask and do the titration with sodium hydroxide (NaOH) as mentioned.

OBSERVATIONS

S.no	Volume of vinegar solution	Burette Reading		Volume of NaOH solution used
		Initial (in mL)	Final (in mL)
1.	20	0	27	27
2.	20	0	27	27
3.	20	0	27	27

Concordant volume = 27 mL

CALCULATIONS

We know that,

^M CH ₃ COOH ^VCH ₃ COOH _ ^M NaOH ^VNaOH Continue reading “Amount of Acetic Acid In Vinegar – Chemistry Project”

Study of  the Adulterants in Food

 

S.No.		Contents	Page No.
I.		Objective
II.		Theory
III.		Experiment 1
IV.		Experiment 2
V.		Experiment 3
VI.		Result
VII.		Conclusion
VIII.		Bibliography

Objective

The Objective of this project is to study some of the common food adulterants present in different food stuffs.

Adulteration in food is normally present in its most crude form; prohibited substances are either added or partly or wholly substituted. Normally the contamination/adulteration in food is done either for financial gain or due to carelessness and lack in a proper hygienic condition of processing, storing, transportation and marketing. This ultimately results that the consumer is either cheated or often become a victim of diseases. Such types of adulteration are quite common in developing countries or backward countries. It is equally important for the consumer to know the common adulterants and their effect on health.

THEORY

The increasing number of food producers and the outstanding amount of import foodstuffs enables the producers to mislead and cheat consumers. To differentiate those who take advantage of legal rules from the ones who commit food adulteration is very difficult. The consciousness of consumers would be crucial. Ignorance and unfair market behaviour may endanger consumer health and misleading can lead to poisoning. So we need simple screening, tests for their detection.

In the past few decades, adulteration of food has become one of the serious problems. Consumption of adulterated food causes serious diseases like cancer, .diarrhoea., , .asthma., .ulcers., etc. Majority of fats, oils and butter are paraffin wax, castor oil and hydrocarbons. Red chilli powder is mixed with brick powder and pepper is mixed with dried papaya seeds. These adulterants can be easily identified by simple chemical tests.

Several agencies .have been set up by the Government of India to remove adulterants from food stuff.

AGMARK – Acronym for agricultural marketing. This organization certifies food products for their quality. Its objective is to promote the Grading and Standardization of agricultural and allied commodities.

EXPERIMENT 1

AIM

To detect the presence of adulterants in fat, oil and butter.

REQUIREMENTS

Test-tube, acetic anhydride, conc. H₂SO₄, acetic acid, conc. HNO₃.

PROCEDURE

Common adulterants present in ghee and oil are paraffin wax, hydrocarbons, dyes and argemone oil. These are detected as follows :

(i)           Adulteration of paraffin wax and hydrocarbon in vegetable ghee
Heat small amount of vegetable ghee with acetic anhydride. Droplets
of oil floating on the surface of unused acetic anhydride indicates the
presence of wax or hydrocarbons.

(ii)          Adulteration of dyes in fat

Heat 1mL of fat with a mixture of 1mL of conc. sulphuric acid and 4mL of acetic acid. Appearance of pink or red colour indicates presence of dye in fat.

(iii)        Adulteration of argemone oil in edible oils

To small amount of oil in a test-tube, add few drops of conc. HNO₃ and shake. Appearance of red colour in the acid layer indicates presence of argemone oil.

EXPERIMENT 2

AIM

To detect the presence of adulterants in sugar

REQUIREMENTS

Test-tubes, dil. HCl.

PROCEDURE

Sugar is usually contaminated with washing soda and other insoluble substances which are detected as follows :

(i)           Adulteration of various insoluble substances in sugar

Take small amount of sugar in a test-tube and shake it with little water. Pure sugar dissolves in water but insoluble impurities do not dissolve.

(ii)         Adulteration of chalk powder, washing soda in sugar

To small amount of sugar in a test-tube, add few drops of dil. HCl. Brisk effervescence of CO₂ shows the presence of chalk powder or washing soda in the given sample of sugar.

EXPERIMENT 3

AIM

To detect the presence of adulterants in samples of chilli powder, turmeric powder and pepper

REQUIREMENTS

Test-tubes, conc. HCl, dil. HNO3, KI solution

PROCEDURE

Common adulterants present in chilli powder, turmeric powder and pepper are red coloured lead salts, yellow lead salts and dried papaya seeds respectively. They are detected as follows :

(i)           Adulteration of red lead salts in chilli powder

To a sample of chilli powder, add dil. HNO₃. Filter the solution and add 2 drops of potassium iodide solution to the filtrate. Yellow ppt. indicates the presence of lead salts in chilli powder.

(ii)         Adulteration of yellow lead salts to turmeric powder

To a sample of turmeric powder add conc. HCl. Appearance of magenta colour shows the presence of yellow oxides of lead in turmeric powder.

(iii)        Adulteration of brick powder in red chilli powder

Add small amount of given red chilli powder in beaker containing water. Brick powder settles at the bottom while pure chilli powder floats over water.

(iv)        Adulteration of dried papaya seeds in pepper

Add small amount of sample of pepper to a beaker containing water and stir with a glass rod. Dried papaya seeds being lighter float over water while pure pepper settles at the bottom.

RESULT

EXPERIMENT	PROCEDURE	OBSERVATION
Adulteration of paraffin wax and hydrocarbon in vegetable ghee.	Heat small amount of vegetable ghee with acetic anhydride. Droplets of oil floating on the surface of unused acetic anhydride indicate the presence of wax or hydrocarbon	Appearance of oil floating on the surface.
Adulteration of dyes in fat	Heat 1mL of fat with a mixture of 1mL of conc. H2SO4 and 4mL of acetic acid.	Appearance of pink colour.
Adulteration of argemone oil in edible oils	To small amount of oil in a test tube, add few drops of conc. HNO3 & shake.	No red colour observed
Adulteration of various insoluble substances in sugar.	Take small amount of sugar in a test tube and shake it with little water.	Pure sugar dissolves in water but insoluble impurities do not dissolve.
Adulteration of chalk powder, washing soda in sugar.	To small amount of sugar in a test tube, add a few drops of dil. HCl.	No brisk effervescence observed.
Adulteration of yellow lead salts to turmeric powder.	To sample of turmeric powder, add conc. HCl.	Appearance of magenta colour.
Adulteration of red lead salts in chilli powder.	To a sample of chilli powder, add dil. HNO3. Filter the solution and add 2 drops of KI solution to the filtrate.	No yellow ppt.
Adulteration of brick powder in chilli powder.	Add small amount of given red chilli powder in a beaker containing water.	Brick powder settles at the bottom while pure chilli powder floats over water.
Adulteration of dried papaya seeds in pepper.	Add small amount of sample of pepper to beaker containing water and stir with a glass rod.	Dried papaya seeds being lighter float over water while pure pepper settles at the bottom.

CONCLUSION

Selection of wholesome and non-adulterated food is essential for daily life to make sure that such foods do not cause any health hazard. It is not possible to ensure wholesome food only on visual examination when the toxic contaminants are present in ppm level. However, visual examination of the food before purchase makes sure to ensure absence of insects, visual fungus, foreign matters, etc. Therefore, due care taken by the consumer at the time of purchase of food after thoroughly examining can be of great help. Secondly, label declaration on packed food is very important for knowing the ingredients and nutritional value. It also helps in checking the freshness of the food and the period of best before use. The consumer should avoid taking food from an unhygienic place and food being prepared under unhygienic conditions. Such types of food may cause various diseases. Consumption of cut fruits being sold in unhygienic conditions should be avoided. It is always better to buy certified food from a reputed shop.

BIBLIOGRAPHY

• NCERT CHEMISTRY XII
• ENCARTA ENCYCLOPEDIA

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