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Investigatory Project on Caffeine in Tea

Determination of caffeine in tea samples Investigatory Project (Class 12)

Tea leaves contain up to 4% caffeine. They also contain tannic acid and colouring matter. The relative amounts of these substances differ in different samples of tea.


Theory:


Caffeine is more soluble in chloroform than in water. So it can be extracted from aqueous solutions by chloroform. But the tannic acid present in tea leaves must be removed before the extraction of caffeine. Tannic acid is removed as calcium tannate.


Aim:


The aim of this experiment is to determine the percentage of caffeine present in different samples of tea leaves and to find out the best tea leaves.


Requirements:


1. Different brands of tea leaves

2. Beakers

3. CaCO3

4. Chloroform


Procedure:


Take 10g each of the given sample of tea leaves and boil with about 100mL of distilled water in a beaker for about 10 minutes. Cool and filter. Add 2g CaCO3 and boil. Remove the precipitated calcium tannate by filtration. Extract the filtrate at least 3 times with chloroform. Distil off the chloroform. The residue is caffeine. Weigh it. In the ssame way, determine the amounts of caffeine in other samples of tea and tabulate.


No:

Brand name of the tea

Mass of tea (x)

Mass of caffeine (y)

% of Caffeine (y x 100)/x

1

2

3

 

 

 

 

 

Conclusion:


The tea containing the highest percentage of caffeine is ……. Hence it is the beast tea among the samples analysed.


VIVA QUESTIONS WITH ANSWERS


1. What is the percentage of caffeine in tea leaves?


Ans: About 4%


2. How will you remove tannic acid from tea leaves?


Ans: By boiling with calcium carbonate


3. What is the product formed when tannic acid is boiled with CaCO3?


Ans: Calcium tannate


4. How will you determine the quality of a sample of tea based on the caffeine content?


Ans: The sample with maximum caffeine content is the best quality tea.


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