Question 1: Chromatography is a technique used to separate the different components of a mixture based on their movement through a medium under the influence of a solvent. It is commonly used to analyse the purity of substances and identify unknown compounds.

Answer: Chromatography separates mixture components based on their movement through a medium influenced by a solvent, used for purity analysis and compound identification.

Question 1: Define the term 'Rf value' in chromatography.

Answer: The Rf value is the ratio of the distance travelled by a substance to the distance travelled by the solvent front in chromatography.

Question 2: Explain why different substances move at different rates during chromatography.

Answer: Different substances move at different rates because of their varying affinities for the stationary phase and solubility in the solvent.

Question 1: A pigment spot travels 3.5 cm from the baseline, and the solvent front moves 10.5 cm. Calculate the Rf value for this pigment.

Answer: Rf = 0.33

Question 2: If a dye mixture shows three spots with Rf values of 0.25, 0.55, and 0.75, which spot is most soluble in the solvent? Explain your answer.

Answer: The spot with Rf 0.75 is most soluble because it travels the furthest with the solvent front.

Question 1: Describe a basic procedure to perform paper chromatography to separate a mixture of inks.

Answer: Apply small spots of the ink mixture onto the baseline of a strip of chromatography paper. Place the paper in a solvent without submerging the ink spots. Allow the solvent to rise and separate the components. Remove the paper once the solvent front is near the top and dry it.

Question 2: List two safety precautions to observe when handling solvents in chromatography experiments.

Answer: Work in a well-ventilated area and wear appropriate protective gear such as gloves and safety goggles.

Question 1: A chromatography experiment results in three distinct spots with Rf values of 0.20, 0.45, and 0.65. The solvent used was water. What can you infer about the polarity of these substances relative to water?

Answer: The substance with Rf 0.20 is more polar (less soluble in water), while the one with Rf 0.65 is less polar (more soluble in water).

Question 1: Describe how chromatography can be used to assess the purity of a sample. (6 marks)

Answer: Chromatography separates the components of a mixture based on their movement through a medium. A pure sample will typically produce a single spot with a consistent Rf value. Multiple spots indicate impurities or a mixture, whereas a single spot suggests high purity.

Question 1: Explain how chromatography is used in the food industry to ensure food additives are safe and correctly labelled.

Answer: Chromatography separates food additives from other ingredients, allowing analysis of their purity and concentration to ensure they meet safety standards and are accurately labelled.