Question 1: Define chromatography and explain how it separates mixtures.

Answer: Chromatography is a technique used to separate the components of a mixture based on their different affinities to a stationary phase and a mobile phase.

Question 2: Describe the role of the stationary phase and the mobile phase in chromatography.

Answer: The stationary phase holds the substances in place, while the mobile phase moves through it, carrying the substances at different rates for separation.

Question 3: What is meant by the term 'retention factor' (Rf) in chromatography?

Answer: Rf is the ratio of the distance travelled by a substance to the distance travelled by the solvent front, used to identify substances.

Question 1: A spot of dye in a chromatography experiment travels 3.5 cm, while the solvent front travels 10 cm. Calculate the Rf value of the dye.

Answer: Rf = 0.35

Question 2: If a pure substance has an Rf value of 0.75 in a particular solvent, but a sample shows an Rf of 0.65, what does this suggest about the sample?

Answer: The sample may be impure or contain additional components that affect its movement on the chromatogram.

Question 1: List three safety precautions to consider when performing paper chromatography in a laboratory.

Answer: Use gloves and eye protection, work in a well-ventilated area, and handle solvents carefully to avoid spills and inhalation hazards.

Question 2: Identify two variables that can be changed to improve the separation of components in chromatography.

Answer: The type of solvent used (mobile phase) and the temperature during the process.

Question 3: Describe the procedure for preparing a chromatography paper for an analysis of a mixture.

Answer: Cut a strip of chromatography paper, draw a pencil line near the bottom as the baseline, spot small amounts of the mixture onto the baseline, and allow the spots to dry before placing it in the solvent to develop.

Question 1: A mixture of substances A, B, and C produces Rf values of 0.2, 0.5, and 0.8 respectively in a given solvent. If a new sample shows peaks at Rf 0.2 and 0.8 only, what can be inferred about the composition of the sample?

Answer: The sample contains substances A and C but not B.

Question 2: During an experiment, the Rf values of a sample vary slightly between runs. What factors could account for these variations?

Answer: Variations could be due to inconsistencies in solvent composition, temperature fluctuations, or differences in paper quality.

Question 1: Explain how chromatography can be used to assess the purity of a substance and discuss its limitations.

Answer: Chromatography separates components in a mixture, allowing identification of impurities based on additional spots. Limitations include overlapping spots, similar Rf values for different substances, and the need for standards for comparison.

Question 2: Describe the process of preparing a chromatography experiment to analyse an unknown dye mixture, including safety and accuracy considerations.

Answer: Prepare the paper by drawing a pencil baseline, spot small amounts of the dye mixture, use appropriate solvents, and conduct the experiment in a well-ventilated area with protective equipment. Ensure consistent application and solvent volume for accuracy.

Question 1: How is chromatography used in the pharmaceutical industry to ensure the purity of medicines?

Answer: Chromatography is used to detect impurities and verify the presence and concentration of active ingredients, ensuring medicines meet purity standards.

Question 2: Discuss how chromatography techniques can be adapted for analysing environmental samples, such as water or soil.

Answer: Chromatography can separate pollutants from environmental samples, allowing detection of contaminants like pesticides or heavy metals. Sample preparation and choosing appropriate solvents are crucial for accurate analysis.