This question is about thin-layer chromatography (TLC) - AQA - A-Level Chemistry - Question 9 - 2019 - Paper 2
Question 9
This question is about thin-layer chromatography (TLC).
A protein was hydrolyzed to form a mixture of amino acids.
A spot of this mixture was added to a TLC plate a... show full transcript
Worked Solution & Example Answer:This question is about thin-layer chromatography (TLC) - AQA - A-Level Chemistry - Question 9 - 2019 - Paper 2
Step 1
Suggest a suitable reagent for the hydrolysis of a protein.
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Answer
A suitable reagent for the hydrolysis of a protein is concentrated hydrochloric acid (HCl). This reagent effectively breaks down proteins into their constituent amino acids.
Step 2
Suggest how the positions of the amino acids on the TLC plate were located.
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Answer
The positions of the amino acids on the TLC plate were located using ninhydrin or ultraviolet light, which allows for the visualization of amino acids that are otherwise colorless.
Step 3
Deduce the minimum number of amino acids present in the original mixture.
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The minimum number of amino acids present in the original mixture can be deduced as 7 or seven, given that there are at least seven distinct spots visible after the TLC process.
Step 4
Suggest why it was necessary to use two different solvents.
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It was necessary to use two different solvents because some of the amino acids did not separate or dissolve with the first solvent. Using a second solvent allows for better separation of compounds that may have similar affinities.
