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 protein structures 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 can be located using ninhydrin or ultraviolet light. Ninhydrin reacts with amino acids to produce visible colored spots, while ultraviolet light can reveal spots UV-active compounds.
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 is 7. This is inferred from the number of distinct spots observed on the TLC plate after separation.
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 amino acids did not separate or dissolve properly with the first solvent. Different solvents can yield better separation by exploiting differing affinities of amino acids for each solvent.
