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Question 1:

What is the stationary phase in Thin-Layer Chromatography (TLC)?

A) Liquid solvent
B) Solid support (usually a plate or sheet)
C) Gas phase
D) Detector

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Explanation: The correct answer is B) Solid support (usually a plate or sheet). In Thin-Layer Chromatography (TLC), the stationary phase is a solid support, commonly a thin layer of adsorbent material coated on a plate or sheet. The most commonly used adsorbent is silica gel, but other materials like alumina and cellulose can also be used. The analyte mixture is applied as spots or bands on the stationary phase for separation and analysis.

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Question 2:

What is the mobile phase in Thin-Layer Chromatography (TLC)?

A) Liquid solvent
B) Solid support (usually a plate or sheet)
C) Gas phase
D) Detector

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Explanation: The correct answer is A) Liquid solvent. In Thin-Layer Chromatography (TLC), the mobile phase is a liquid solvent or a mixture of solvents. The mobile phase moves through the stationary phase by capillary action, carrying the analyte spots or bands along. The choice of mobile phase and its composition depends on the analytes to be separated and their desired retention and resolution.

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Question 3:

How are analytes separated in Thin-Layer Chromatography (TLC)?

A) By partitioning between the mobile phase and the stationary phase
B) By size exclusion
C) By ion exchange
D) By affinity interactions

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Explanation: The correct answer is A) By partitioning between the mobile phase and the stationary phase. In Thin-Layer Chromatography (TLC), analytes are separated based on their partitioning or distribution between the mobile phase and the stationary phase. The analytes with higher affinity for the mobile phase will move faster, while those with higher affinity for the stationary phase will move slower. This differential partitioning leads to the separation of analyte spots or bands on the TLC plate.

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Question 4:

How are analytes visualized in Thin-Layer Chromatography (TLC)?

A) By measuring the absorbance of light
B) By spraying with a specific reagent or dye
C) By measuring the electrical conductivity
D) By measuring the mass spectrometry signal

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Explanation: The correct answer is B) By spraying with a specific reagent or dye. In Thin-Layer Chromatography (TLC), analytes are visualized by spraying the TLC plate with a specific reagent or dye that reacts with the analytes. This reaction produces colored spots or bands corresponding to the separated analytes. The reagent or dye selectively reacts with the analytes, making them visible for qualitative or quantitative analysis.

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Question 5:

What does Rf value represent in Thin-Layer Chromatography (TLC)?

A) The distance traveled by the mobile phase
B) The distance traveled by the stationary phase
C) The ratio of the distance traveled by the analyte to the distance traveled by the mobile phase
D) The ratio of the distance traveled by the analyte to the distance traveled by the stationary phase

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Explanation: The correct answer is C) The ratio of the distance traveled by the analyte to the distance traveled by the mobile phase. Rf value (Retention Factor) in Thin-Layer Chromatography (TLC) represents the ratio of the distance traveled by the analyte spot or band to the distance traveled by the mobile phase. It is calculated by dividing the distance from the application point to the center of the spot or band by the distance from the application point to the solvent front. Rf value is a characteristic property of each analyte and can be used for identification and comparison.