I need help in answering my caffeine extraction lab report. Please answer the qu

Question

I need help in answering my caffeine extraction lab report. Please answer the question.

Was caffeine successfully isolated from tea?

How efficient was the isolation of caffeine from tea (compare % with 2-5% given in text)? Possible sources of loss?

How efficient was the vacuum sublimation? Possible sources of loss?

Was the caffeine obtained pure? Based on % error of mp, mp range?

What are possible impurities?

Tea in tea bag mass

2.312 g

Crude caffeine mass

0.04500 g

Pure caffeine mass

0.02800 g

Crude caffeine Melting point

235.6 °C

Pure caffeine Melting point (experimental)

233.3 °C

Pure caffeine Melting point (theoretical)

236.0 °C

Melting point range

232.1 - 233.3 °C

Melting point percent errors

1.144 %

Pure caffeine from tea percent recovery

1.211 %

Pure caffeine from crude percent recovery

62.22 %

Was caffeine successfully isolated from tea?

Tea in tea bag mass

2.312 g

Crude caffeine mass

0.04500 g

Pure caffeine mass

0.02800 g

Crude caffeine Melting point

235.6 °C

Pure caffeine Melting point (experimental)

233.3 °C

Pure caffeine Melting point (theoretical)

236.0 °C

Melting point range

232.1 - 233.3 °C

Melting point percent errors

1.144 %

Pure caffeine from tea percent recovery

1.211 %

Pure caffeine from crude percent recovery

62.22 %

Explanation / Answer

To measure how successfully caffeine was isolated from tea we look for recovery % values
which according to your result is 62.22 % . This is value seems to pretty good because 100%
recovery is impossible. If the value is around 70-75% then your experiment will be successful.

The error % which is 1.211% is less than 2 % so we can say that the isolation is efficient.
If the value lies in between 2-5% then it is less efficient, above 5% indicates experimental errors.
Possible source of loss could be due to calibration error, diluting beyond limits with water.

For high-boiing and sensitive materials like caffeine this method is very effective.
Possible sources of loss could be : dichloromethane could be left out in the caffeine as impurity,
loss of product is more in this case.

Difference in the MP range = 233.3-232.1 = 1.2oC
If this difference is greater than 5oC then the substance is impure otherwise pure.
Hence, the caffeine obtained is pure and it is within in the acceptable range.

Possible impurities could be : Dichloromethane, drying agents like CaCl2, to make it basic
medium bases like Na2CO3 are added which can be a impurity.

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