Explain how paper and thin-layer chromatography separate a mixture through the different attractions of components to the mobile and stationary phases, and calculate and interpret retardation factor (Rf) values from a chromatogram.
Tę umiejętność sprawdza 17 zadań wzorowanych na arkuszach IB z lat 2023–2026.
A mixture of compounds X and Y is analysed by thin layer chromatography. The stationary phase is silica gel and the solvent used is hexane. The chromatogram is shown. Which option is consistent with this chromatogram? A. RF of Y is 0.80; compound Y…
A paper chromatogram is shown. The distances marked were measured along the paper. What is the retardation factor, RF, of compound Y? A. 0.40 B. 0.60 C. 0.70 D. 1.67
A mixture of biphenyl, C12H10, and 4-phenylphenol, C12H10O, was separated by thin-layer chromatography on a polar silica plate, using the non-polar solvent cyclohexane as the mobile phase. What are the position and the retardation factor…
Each beaker used as a chromatography chamber was covered with a watch glass while the solvent rose up the paper. Explain why the chamber has to be covered for the experiment to be properly designed.
Explain why the start line must be horizontal and must be above the level of the solvent when the strip is placed in the chamber.
For the orange dye, calculate the retardation factor, RF, obtained in each solvent system.
Deduce, giving a reason, which of the two dyes, orange or violet, is the more polar.
The student suspected that the ink contained more than four dyes, and that one of the spots was two dyes that had not separated. Suggest how the student could modify the chromatography experiment to test this idea.
Explain how the dyes are separated from one another in paper chromatography.
Two pigments extracted from a leaf are separated by thin-layer chromatography on a silica plate (a polar stationary phase) using a non-polar solvent as the mobile phase. Pigment X travels further up the plate than pigment Y. Which statement explains the…
A student used thin-layer chromatography to investigate the artificial colourings in a boiled sweet. A solution of the sweet was spotted on the start line and the plate was developed. The developed chromatogram is shown with a ruler in centimetres, whose zero…
A student separates the coloured dyes in a sample of black ink by paper chromatography, using water as the solvent. Explain how paper chromatography can separate and identify the dyes in a mixture.
Determine the identity of the amino acid in spot B by calculating its RF value from the chromatogram.
Spot X is known to be either glutamine or isoleucine. The structures of the two amino acids are shown. Predict, with reference to the structures, which amino acid is more likely to be in spot X. Use the RF values in the table.
A laboratory tests a urine sample for steroid drugs. Before the compounds in the extract are identified, they must be separated from one another. State a technique that can be used to separate the compounds.
A sample of the protein is completely hydrolysed to a mixture of amino acids. Outline how paper chromatography can be used to identify the amino acids in this mixture when samples of the pure amino acids are available for comparison.
A biochemist wants to find out which of the amino acids glycine, serine and leucine are present in a short peptide. Outline how paper chromatography can be used to do this.
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