Three samples containing amino acids are analysed using paper chromatography. Sample 1 contains starting material. Sample 2 contains the reaction mixture. Sample 3 contains the product. The resulting chromatogram is shown below. From the chromatogram it could be concluded

Question

BlackTom AI · Accepted Answer

To analyze the chromatogram properly, I will evaluate each option against what the three samples represent and what the spots indicate.

Option a: 'the reaction has formed a different product.' If a different product had formed entirely, we would expect the reaction mixture (sample 2) to show a spot corresponding to the new product with a distinct Rf value, and the starting material spot might disappear or be greatly reduced. However, the description and the chromatogram suggest that the reaction mixture still shows unreacted starting material, meaning the starting material spot remains. Therefore, this option is not supported by the chromatogram.

Option b: 'the reaction has gone to completion.' Completion would mean no starting material remains in the reaction mixture (sample 2), with only the product spot present. Since the chromatogram shows a spot matching the starting material in sample 2, this option is contradicted by the data.

Option c: 'the reaction mixture still has unreacted starting material.' This statement aligns with the observation that sample 2 contains a spot at the same Rf as the starting material in sample 1, indicating that some starting material remains unreacted. It is a direct, data-supported interpretation of the chromatogram.

Option d: 'there is a large amount of starting material left to react.' While the presence of starting material shows incomplete reaction, the chromatogram alone does not provide quantitative information to claim a large amount, so this statement goes beyond what can be concluded from the image. It assumes a proportion that cannot be inferred from the visual spots without calibration or intensity data.

In summary, the key reasoning hinges on whether sample 2 contains the starting material spot that matches sample 1. The chromatogram indicates that the reaction mixture still contains unreacted starting material, which rules out completion and the idea of a different product dominating, while the claim of a large remaining amount cannot be justified from the provided image alone. Therefore, option c is the data-consistent conclusion, while the others either contradict the observed spots or over-interpret the data.

Three samples containing amino acids are analysed using paper chromatography. Sample 1 contains starting material. Sample 2 contains the reaction mixture. Sample 3 contains the product. The resulting chromatogram is shown below. From the chromatogram it could be concluded单项选择题

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